485BPOS

File Nos. 2-98772
811-04347

AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION
ON JULY 22, 2011

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

Pre-Effective Amendment No. __                                                                                                                                                                    o

Post-Effective Amendment No. 148                                                                                                       þ

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940

Amendment No. 187                                                                                                                                þ

GMO TRUST

(Exact Name of Registrant as Specified in Charter)

40 Rowes Wharf, Boston, Massachusetts 02110
(Address of principal executive offices)

617-330-7500
(Registrant’s telephone number, including area code)

with a copy to:

J.B. Kittredge, Esq.
GMO Trust
40 Rowes Wharf
Boston, Massachusetts 02110 Thomas R. Hiller, Esq.
Ropes & Gray LLP
Prudential Tower
800 Boylston Street
Boston, Massachusetts 02199

(Name and address of agents for service)

It is proposed that this filing will become effective:

þ      Immediately upon filing pursuant to paragraph (b), or

o      60 days after filing pursuant to paragraph (a)(1), or

o      On __________, pursuant to paragraph (b), or

o      75 days after filing pursuant to paragraph (a)(2), of Rule 485.

This filing relates only to the 48 series of the Registrant listed on the front cover of the GMO Trust Prospectus, dated June 30, 2011, and filed with the Securities and Exchange Commission on June 29, 2011 with Post-Effective Amendment No. 146 under the Securities Act of 1933, as amended, and Amendment No. 185 under the Investment Company Act of 1940, as amended.

GMO TRUST

SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933 (the “Securities Act”) and the Investment Company Act of 1940 (the “1940 Act”), each as amended, the Registrant, GMO Trust, certifies that it meets all of the requirements for effectiveness of this Registration Statement under Rule 485(b) under the Securities Act and has duly caused this Post-Effective Amendment No. 148 under the Securities Act and Amendment No. 187 under the 1940 Act to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Boston and The Commonwealth of Massachusetts, on the 22nd day of July, 2011.

GMO Trust
By:	J.B. KITTREDGE*
	J.B. Kittredge
	Title:	President; Chief Executive Officer; Principal Executive Officer

     Pursuant to the requirements of the Securities Act, this Post-Effective Amendment No. 148 to GMO Trust’s Registration Statement under the Securities Act has been signed below by the following persons in the capacities and on the date indicated.

Signatures	Title	Date
J.B. KITTREDGE* J.B. Kittredge	Trustee; President; Chief Executive  Officer; Principal Executive Officer	July 22, 2011
SHEPPARD N. BURNETT* Sheppard N. Burnett	Treasurer; Chief Financial Officer;  Principal Financial and Accounting Officer	July 22, 2011
DONALD W. GLAZER* Donald W. Glazer	Trustee	July 22, 2011
PETER TUFANO* Peter Tufano	Trustee	July 22, 2011
PAUL BRAVERMAN* Paul Braverman	Trustee	July 22, 2011

*By:	/s/ JASON HARRISON
	Jason Harrison
	Attorney-in-Fact**

** Pursuant to Powers of Attorney for each of Donald W. Glazer and Peter Tufano filed with the SEC as part of Post-Effective Amendment No. 138 to the Registration Statement under the 1933 Act and Amendment No. 173 to the Registration Statement under the 1940 Act on September 29, 2009, pursuant to Powers of Attorney for each of Sheppard N. Burnett and J.B. Kittredge (in his capacity as President, Chief Executive Officer, and Principal Executive Officer) filed with the SEC as part of Post-Effective Amendment No. 139 to the Registration Statement under the 1933 Act and Amendment No. 174 to the Registration Statement under the 1940 Act on October 30, 2009, and pursuant to Powers of Attorney for each of Paul Braverman and J.B. Kittredge (in his capacity as Trustee) filed with the SEC as part of Post-Effective Amendment No. 140 to the Registration Statement under the 1933 Act and Amendment No. 176 to the Registration Statement under the 1940 Act on April 30, 2010.

GMO TRUST JULY 2011 ANNUAL UPDATE 485(b) XBRL FILING

EXHIBIT INDEX

GMO TRUST

Exhibit Ref.	Title of Exhibit
EX-101.INS	XBRL Instance Document
EX-101.SCH	XBRL Taxonomy Extension Schema Document
EX-101.CAL	XBRL Taxonomy Extension Calculation Linkbase
EX.101.DEF	XBRL Taxonomy Extension Definition Linkbase
EX.101.LAB	XBRL Taxonomy Extension Labels Linkbase
EX-101.PRE	XBRL Taxonomy Extension Presentation Linkbase
Other.
1	Certificate of Clerk of the Trust certifying resolution by the Board of Trustees of the Trust required pursuant to Rule 483 under the Securities Act of 1933.

EX-99.1

GMO TRUST

CERTIFICATE OF CLERK

          I, Jason Harrison, hereby certify that I am the duly elected and acting Clerk of GMO Trust, a Massachusetts business trust (the “Trust”), and do hereby further certify as follows:

          1. Attached hereto as Exhibit A is a true and correct copy of a resolution from the meeting of the Board of Trustees of the Trust (the “Board”) held September 10, 2009 (the “Meeting”). The resolution was duly adopted by the Board at the Meeting. Such resolution has not been modified or rescinded since its adoption and is in full force and effect as of the date hereof.

          IN WITNESS WHEREOF, I have hereunto set my hand this 22nd day of July, 2011.

By:	/S/ JASON HARRISON
	Name:	Jason Harrison
	Title:	Clerk

Exhibit A

Resolution of the Board — September 10, 2009

                  Authorization of Power of Attorney

VOTED: That each of Sheppard N. Burnett and Jason Harrison be, and each of them acting singly hereby is, authorized to sign for J.B. Kittredge, in his name and in the capacity of President, Chief Executive Officer and Principal Executive Officer, on behalf of the Trust, any and all amendments to the Trust’s Registration Statement filed with the Securities and Exchange Commission, pursuant to a power of attorney executed by Mr. Kittredge.

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GMO U.S. CORE EQUITY FUND

GMO U.S. CORE EQUITY FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO U.S. CORE EQUITY FUND		Class III, GMO U.S. Core Equity Fund	Class IV, GMO U.S. Core Equity Fund	Class V, GMO U.S. Core Equity Fund	Class VI, GMO U.S. Core Equity Fund
Operating Expenses Column [Text]		Class III	Class IV	Class V	Class VI
Management fee		0.31%	0.31%	0.31%	0.31%
Shareholder service fee		0.15%	0.10%	0.085%	0.055%
Other expenses		0.03%	0.03%	0.03%	0.03%
Total annual operating expenses		0.49%	0.44%	0.43%	0.40%
Expense reimbursement	[1]	(0.03%)	(0.03%)	(0.03%)	(0.03%)
Total annual operating expenses after expense reimbursement		0.46%	0.41%	0.40%	0.37%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO U.S. CORE EQUITY FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO U.S. Core Equity Fund	Class III	47	[1]	154	271	613
Class IV, GMO U.S. Core Equity Fund	Class IV	42	[1]	138	243	552
Class V, GMO U.S. Core Equity Fund	Class V	41	[1]	135	238	539
Class VI, GMO U.S. Core Equity Fund	Class VI	38	[1]	125	221	502

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 96% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[1]

Highest Quarter: 16.59% (2Q2003)

Lowest Quarter: -17.14% (3Q2002)

Year-to-Date (as of 3/31/11): 4.41%

Average Annual Total Returns Periods Ending December 31, 2010

^[1]

Average Annual Total Returns GMO U.S. CORE EQUITY FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO U.S. Core Equity Fund	Class III	Return Before Taxes		8.82%	0.46%	0.88%	10.73%	Sep. 18, 1985
Return Before Taxes Class IV, GMO U.S. Core Equity Fund	Class IV	Return Before Taxes		8.84%	0.52%	0.93%	4.20%	Jan. 09, 1998
Return Before Taxes Class VI, GMO U.S. Core Equity Fund	Class VI	Return Before Taxes		8.95%	0.57%		3.96%	Jun. 30, 2003
Return After Taxes on Distributions Class III, GMO U.S. Core Equity Fund	Class III	Return After Taxes on Distributions		8.55%	(0.30%)	0.29%	7.93%	Sep. 18, 1985
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO U.S. Core Equity Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.05%	0.31%	0.62%	8.11%	Sep. 18, 1985
S&P 500 Index Class III, GMO U.S. Core Equity Fund	Class III	S&P 500 Index	(reflects no deduction for fees, expenses or taxes)	15.06%	2.29%	1.41%	10.52%	Sep. 18, 1985
S&P 500 Index Class IV, GMO U.S. Core Equity Fund	Class IV	S&P 500 Index	(reflects no deduction for fees, expenses or taxes)	15.06%	2.29%	1.41%	4.18%	Jan. 09, 1998
S&P 500 Index Class VI, GMO U.S. Core Equity Fund	Class VI	S&P 500 Index	(reflects no deduction for fees, expenses or taxes)	15.06%	2.29%		5.55%	Jun. 30, 2003

GMO TOBACCO-FREE CORE FUND

GMO TOBACCO-FREE CORE FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO TOBACCO-FREE CORE FUND Class III, GMO Tobacco-Free Core Fund
Operating Expenses Column [Text]		Class III
Management fee		0.33%
Shareholder service fee		0.15%
Other expenses		0.53%
Total annual operating expenses		1.01%
Expense reimbursement	[1]	(0.53%)
Total annual operating expenses after expense reimbursement		0.48%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO TOBACCO-FREE CORE FUND Class III, GMO Tobacco-Free Core Fund	Class III	49	[1]	271	511	1,199

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 87% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund's investment objective by investing primarily in U.S. equities or groups of U.S. equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets, and expects to invest substantially all of its assets, in investments in tobacco-free companies (see “Name Policies”). For these purposes, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts, and the term “tobacco-free companies” refers to companies that are not listed in the Tobacco Producing Issuer industry classification maintained by Ford Investor Services.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 15.80% (2Q2003)

Lowest Quarter: -17.27% (3Q2002)

Year-to-Date (as of 3/31/11): 4.43%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO TOBACCO-FREE CORE FUND Class III, GMO Tobacco-Free Core Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		9.28%	1.53%	1.05%	8.97%	Oct. 31, 1991
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		9.03%	0.72%	0.41%	6.49%	Oct. 31, 1991
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.33%	1.21%	0.74%	6.60%	Oct. 31, 1991
S&P 500 Index	Class III	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%	2.29%	1.41%	8.43%	Oct. 31, 1991

GMO QUALITY FUND

GMO QUALITY FUND

Investment objective

Total return.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO QUALITY FUND		Class III, GMO Quality Fund	Class IV, GMO Quality Fund	Class V, GMO Quality Fund	Class VI, GMO Quality Fund
Operating Expenses Column [Text]		Class III	Class IV	Class V	Class VI
Management fee		0.33%	0.33%	0.33%	0.33%
Shareholder service fee		0.15%	0.105%	0.085%	0.055%
Other expenses		0.02%	0.02%	0.02%	0.02%
Total annual operating expenses		0.50%	0.46%	0.44%	0.41%
Expense reimbursement	[1]	(0.02%)	(0.02%)	(0.02%)	(0.02%)
Total annual operating expenses after expense reimbursement		0.48%	0.44%	0.42%	0.39%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO QUALITY FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Quality Fund	Class III	49	[1]	158	278	626
Class IV, GMO Quality Fund	Class IV	45	[1]	146	256	577
Class V, GMO Quality Fund	Class V	43	[1]	139	244	553
Class VI, GMO Quality Fund	Class VI	40	[1]	130	228	516

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes to be of high quality.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In assessing a company’s quality, the Manager may consider several factors, including in particular, high return on equity, low debt to equity and the Manager’s assessment of the company relative to its competitors.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund may hold fewer than 100 stocks. The Fund may make tactical allocations of up to 20% of its net assets to investments in cash and high quality debt instruments.

The Fund is permitted to invest directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to any country in the world, including emerging countries. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Focused Investment Risk – Focusing investments in a limited number of countries, sectors or companies or in industries with high positive correlations to one another creates additional risk. The Fund invests its assets in the securities of a limited number of issuers, and a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund invested in the securities of a larger number of issuers.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Funds foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance. Performance information (before and after taxes) for certain periods reflects performance achieved prior to the change in the Fund’s principal investment strategies, effective June 1, 2009.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 11.53% (3Q2010)

Lowest Quarter: -13.13% (4Q2008)

Year-to-Date (as of 3/31/11): 3.48%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO QUALITY FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Quality Fund	Class III	Return Before Taxes		5.47%	2.77%		2.31%	Feb. 06, 2004
Return Before Taxes Class IV, GMO Quality Fund	Class IV	Return Before Taxes		5.51%	2.80%		2.35%	Feb. 06, 2004
Return Before Taxes Class V, GMO Quality Fund	Class V	Return Before Taxes		5.53%			0.75%	Dec. 08, 2006
Return Before Taxes Class VI, GMO Quality Fund	Class VI	Return Before Taxes		5.57%			0.78%	Dec. 08, 2006
Return After Taxes on Distributions Class III, GMO Quality Fund	Class III	Return After Taxes on Distributions		5.17%	2.44%		2.02%	Feb. 06, 2004
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Quality Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		3.91%	2.41%		2.00%	Feb. 06, 2004
S&P 500 Index Class III, GMO Quality Fund	Class III	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%	2.29%		3.47%	Feb. 06, 2004
S&P 500 Index Class IV, GMO Quality Fund	Class IV	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%	2.29%		3.47%	Feb. 06, 2004
S&P 500 Index Class V, GMO Quality Fund	Class V	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%			(0.65%)	Dec. 08, 2006
S&P 500 Index Class VI, GMO Quality Fund	Class VI	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%			(0.65%)	Dec. 08, 2006

GMO U.S. INTRINSIC VALUE FUND

GMO U.S. INTRINSIC VALUE FUND

Investment objective

Long-term capital growth.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. INTRINSIC VALUE FUND Class III, GMO U.S. Intrinsic Value Fund
Operating Expenses Column [Text]		Class III
Management fee		0.31%
Shareholder service fee		0.15%
Other expenses		1.30%
Total annual operating expenses		1.76%
Expense reimbursement	[1]	(1.30%)
Total annual operating expenses after expense reimbursement		0.46%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	1 Year		3 Years	5 Years	10 Years
GMO U.S. INTRINSIC VALUE FUND Class III, GMO U.S. Intrinsic Value Fund	47	[1]	427	832	1,965

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 53% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[2]

Highest Quarter: 19.25% (2Q2003)

Lowest Quarter: -18.29% (4Q2008)

Year-to-Date (as of 3/31/11): 9.10%

Average Annual Total Returns Periods Ending December 31, 2010

^[2]

Average Annual Total Returns GMO U.S. INTRINSIC VALUE FUND Class III, GMO U.S. Intrinsic Value Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		11.59%	(0.58%)	2.74%	3.24%	Aug. 02, 1999
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		11.31%	(1.79%)	1.43%	1.99%	Aug. 02, 1999
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		7.82%	(0.65%)	2.05%	2.46%	Aug. 02, 1999
Russell 1000 Value Index	Class III	Russell 1000 Value Index	(reflects no deduction for fees, expenses, or taxes)	15.51%	1.28%	3.26%	3.27%	Aug. 02, 1999

GMO U.S. GROWTH FUND

GMO U.S. GROWTH FUND

Investment objective

Long-term capital growth.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. GROWTH FUND Class III, GMO U.S. Growth Fund
Operating Expenses Column [Text]		Class III
Management fee		0.31%
Shareholder service fee		0.15%
Other expenses	[1]	4.82%
Total annual operating expenses		5.28%
Expense reimbursement	[2]	(4.81%)
Total annual operating expenses after expense reimbursement		0.47%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO U.S. GROWTH FUND Class III, GMO U.S. Growth Fund	Class III	48	[1]	1,149	2,243	4,953

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[3]

Highest Quarter: 15.03% (2Q2003)

Lowest Quarter: -21.46% (1Q2001)

Year-to-Date (as of 3/31/11): 4.78%

Average Annual Total Returns Periods Ending December 31, 2010

^[3]

Average Annual Total Returns GMO U.S. GROWTH FUND Class III, GMO U.S. Growth Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		13.94%	1.31%	(0.78%)	9.58%	Dec. 30, 1988
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		13.75%	0.88%	(1.31%)	5.35%	Dec. 30, 1988
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		9.29%	1.08%	(0.80%)	6.23%	Dec. 30, 1988
Russell 1000 Growth Index	Class III	Russell 1000 Growth Index	(reflects no deduction for fees, expenses, or taxes)	16.71%	3.75%	0.02%	9.04%	Dec. 30, 1988

GMO U.S. SMALL/MID CAP VALUE FUND

GMO U.S. SMALL/MID CAP VALUE FUND

Investment objective

Long-term capital growth.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO U.S. SMALL/MID CAP VALUE FUND Class III, GMO U.S. Small/Mid Cap Value Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. SMALL/MID CAP VALUE FUND Class III, GMO U.S. Small/Mid Cap Value Fund
Operating Expenses Column [Text]		Class III
Management fee		0.31%
Shareholder service fee		0.15%
Other expenses	[1]	1.77%
Total annual operating expenses		2.23%
Expense reimbursement	[2]	(1.76%)
Total annual operating expenses after expense reimbursement		0.47%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO U.S. SMALL/MID CAP VALUE FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO U.S. Small/Mid Cap Value Fund USD ($)		Class III	150	[1]	630	1,136	2,531		Class III	98	[1]	575	1,078	2,464

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 106% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 2500 Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of U.S. companies that issue stocks included in the Russell 2500 Index, a U.S. stock index, and in companies with similar market capitalizations (“small- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments in small- and mid-cap companies tied economically to the U.S. (see “Name Policies”). As of May 31, 2011, the market capitalization of companies that issue stocks included in the Russell 2500 Index ranged from approximately $11.9 million to $11.7 billion, with an average market capitalization of approximately $3.1 billion and a median market capitalization of approximately $2.8 billion. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[4]

Highest Quarter: 23.22% (2Q2003)

Lowest Quarter: -20.74% (4Q2008)

Year-to-Date (as of 3/31/11): 8.05%

Average Annual Total Returns Periods Ending December 31, 2010

^[4]

Average Annual Total Returns GMO U.S. SMALL/MID CAP VALUE FUND Class III, GMO U.S. Small/Mid Cap Value Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		24.89%	0.21%	6.42%	10.80%	Dec. 31, 1991
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		24.71%	(0.78%)	4.04%	7.87%	Dec. 31, 1991
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		15.96%	(0.03%)	4.79%	8.21%	Dec. 31, 1991
Russell 2500 Value Index (Fund benchmark)	Class III	Russell 2500 Value Index (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	24.82%	3.85%	8.53%	11.90%	Dec. 31, 1991
Russell 2500 Value + Index (Composite index)	Class III	Russell 2500 Value + Index (Composite index)		24.82%	3.85%	8.53%	11.28%	Dec. 31, 1991

GMO U.S. SMALL/MID CAP GROWTH FUND

GMO U.S. SMALL/MID CAP GROWTH FUND

Investment objective

Long-term capital growth.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO U.S. SMALL/MID CAP GROWTH FUND Class III, GMO U.S. Small/Mid Cap Growth Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. SMALL/MID CAP GROWTH FUND Class III, GMO U.S. Small/Mid Cap Growth Fund
Operating Expenses Column [Text]		Class III
Management fee		0.31%
Shareholder service fee		0.15%
Other expenses	[1]	2.73%
Total annual operating expenses		3.19%
Expense reimbursement	[2]	(2.72%)
Total annual operating expenses after expense reimbursement		0.47%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO U.S. SMALL/MID CAP GROWTH FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO U.S. Small/Mid Cap Growth Fund USD ($)		Class III	150	[1]	827	1,530	3,400		Class III	98	[1]	773	1,474	3,339

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 136% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 2500 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of U.S. companies that issue stocks included in the Russell 2500 Index, a U.S. stock index, and in companies with similar market capitalizations (“small- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments in small- and mid-cap companies tied economically to the U.S. (see “Name Policies”). As of May 31, 2011, the market capitalization of companies that issue stocks included in the Russell 2500 Index ranged from approximately $11.9 million to $11.7 billion, with an average market capitalization of approximately $3.1 billion and a median market capitalization of approximately $2.8 billion. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[5]

Highest Quarter: 22.74% (2Q2003)

Lowest Quarter: -27.98% (4Q2008)

Year-to-Date (as of 3/31/11): 14.43%

Average Annual Total Returns Periods Ending December 31, 2010

^[5]

Average Annual Total Returns GMO U.S. SMALL/MID CAP GROWTH FUND Class III, GMO U.S. Small/Mid Cap Growth Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		32.07%	0.94%	3.36%	5.60%	Dec. 31, 1996
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		32.00%	(0.64%)	1.89%	0.75%	Dec. 31, 1996
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		20.46%	0.36%	2.45%	2.35%	Dec. 31, 1996
Russell 2500 Growth Index	Class III	Russell 2500 Growth Index	(reflects no deduction for fees, expenses, or taxes)	28.86%	5.63%	4.19%	6.22%	Dec. 31, 1996

GMO REAL ESTATE FUND

GMO REAL ESTATE FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO REAL ESTATE FUND Class III, GMO Real Estate Fund
Operating Expenses Column [Text]		Class III
Management fee		0.33%
Shareholder service fee		0.15%
Other expenses		0.58%
Total annual operating expenses		1.06%
Expense reimbursement	[1]	(0.58%)
Total annual operating expenses after expense reimbursement		0.48%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO REAL ESTATE FUND Class III, GMO Real Estate Fund	Class III	49	[1]	282	533	1,252

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 25% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in investments or groups of investments that the Manager believes will provide higher returns than the MSCI U.S. REIT Index.

The Manager uses active investment management methods, which means that investments are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting investments for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify investments that the Manager believes present positive return potential relative to other investments. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an investment or a group of investments. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an investment or group of investments relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund has a fundamental policy to concentrate its investments in real estate-related investments. Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in real estate investment trusts (“REITs”) and other real estate-related investments (see “Name Policies”). REITs are managed vehicles that invest in real estate or real estate-related investments (both equity and fixed income securities). For purposes of this Prospectus, the term “real estate-related investments” includes securities of REITs and of companies that derive at least 50% of their revenues and profits from, or have at least 50% of their assets invested in, (i) the development, construction, management, or sale of real estate or (ii) real estate holdings.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended (the “1940 Act”), and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Real Estate Risk – Real estate-related investments may decline in value as a result of factors affecting the real estate industry, such as the supply of real property in particular markets, changes in zoning laws, delays in completion of construction, changes in real estate values, changes in property taxes, levels of occupancy, adequacy of rent to cover operating expenses, and local and regional market conditions. The value of real estate-related investments also may be affected by changes in interest rates and social and economic trends. REITs are subject to the risk of fluctuations in income from underlying real estate assets, their inability to manage effectively the cash flows generated by those assets, prepayments and defaults by borrowers, and failing to qualify for the special tax treatment granted to REITs under the Internal Revenue Code of 1986 and/or to maintain exempt status under the 1940 Act.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Models that have demonstrated an ability to explain prior market data often fail to accurately predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Focused Investment Risk – Focusing investments in sectors and industries with high positive correlations to one another creates additional risk. The Fund’s concentration in real estate-related investments make the Fund’s net asset value more susceptible to economic, market, political and other developments affecting the real estate industry.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Fund’s benchmark, which more accurately reflects the Fund’s investments. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 32.69% (3Q2009)

Lowest Quarter: -35.42% (4Q2008)

Year-to-Date (as of 3/31/11): 6.58%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO REAL ESTATE FUND Class III, GMO Real Estate Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		27.40%	3.52%	9.98%	9.34%	May 31, 1996
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		25.92%	(0.12%)	6.85%	6.37%	May 31, 1996
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		17.68%	1.57%	7.47%	6.79%	May 31, 1996
MSCI U.S. REIT Index (Fund benchmark)	Class III	MSCI U.S. REIT Index (Fund benchmark)	(returns reflect no deduction for fees, expenses, or taxes)	28.48%	2.99%	10.57%	10.42%	May 31, 1996
S&P 500 Index	Class III	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%	2.29%	1.41%	6.29%	May 31, 1996

GMO TAX-MANAGED U.S. EQUITIES FUND

GMO TAX-MANAGED U.S. EQUITIES FUND

Investment objective

High after-tax total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO TAX-MANAGED U.S. EQUITIES FUND Class III, GMO Tax-Managed U.S. Equities Fund
Operating Expenses Column [Text]		Class III
Management fee		0.33%
Shareholder service fee		0.15%
Other expenses		0.56%
Total annual operating expenses		1.04%
Expense reimbursement	[1]	(0.56%)
Total annual operating expenses after expense reimbursement		0.48%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO TAX-MANAGED U.S. EQUITIES FUND Class III, GMO Tax-Managed U.S. Equities Fund	Class III	49	[1]	277	524	1,231

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 70% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 3000 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

The Manager considers the tax effects of a proposed trade in conjunction with the return forecast of the identified equities, and their potential contribution to the overall portfolio. The Manager also may consider the Fund’s realized and unrealized gains and losses, and current market conditions, because these factors also influence the decision to buy or sell securities.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. There can be no assurance that the Fund’s tax management strategies will be effective, and you may incur tax liabilities that exceed your economic return. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Models that have demonstrated an ability to explain prior market data often fail to accurately predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares (Before Tax) Years Ending December 31

Highest Quarter: 16.69% (2Q2003)

Lowest Quarter: -17.54% (3Q2002)

Year-to-Date (as of 3/31/11): 3.92%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO TAX-MANAGED U.S. EQUITIES FUND Class III, GMO Tax-Managed U.S. Equities Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		8.81%	0.36%	0.53%	2.71%	Jul. 23, 1998
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		8.54%	0.07%	0.22%	2.36%	Jul. 23, 1998
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.05%	0.30%	0.37%	2.22%	Jul. 23, 1998
Russell 3000 Index (Fund benchmark)	Class III	Russell 3000 Index (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	16.93%	2.74%	2.16%	3.25%	Jul. 23, 1998
Russell 3000 + Index (Composite index)	Class III	Russell 3000 + Index (Composite index)		16.93%	2.77%	1.65%	2.78%	Jul. 23, 1998

GMO INTERNATIONAL CORE EQUITY FUND

GMO INTERNATIONAL CORE EQUITY FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO INTERNATIONAL CORE EQUITY FUND		Class III, GMO International Core Equity Fund	Class IV, GMO International Core Equity Fund	Class VI, GMO International Core Equity Fund
Operating Expenses Column [Text]		Class III	Class IV	Class VI
Management fee		0.38%	0.38%	0.38%
Shareholder service fee		0.15%	0.09%	0.055%
Other expenses		0.05%	0.05%	0.05%
Total annual operating expenses		0.58%	0.52%	0.49%
Expense reimbursement	[1]	(0.05%)	(0.05%)	(0.05%)
Total annual operating expenses after expense reimbursement		0.53%	0.47%	0.44%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL CORE EQUITY FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO International Core Equity Fund	Class III	54	[1]	181	319	721
Class IV, GMO International Core Equity Fund	Class IV	48	[1]	162	286	648
Class VI, GMO International Core Equity Fund	Class VI	45	[1]	152	269	611

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[6]

Highest Quarter: 22.30% (2Q2009)

Lowest Quarter: -19.92% (3Q2008)

Year-to-Date (as of 3/31/11): 3.48%

Average Annual Total Returns Periods Ending December 31, 2010

^[6]

Average Annual Total Returns GMO INTERNATIONAL CORE EQUITY FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO International Core Equity Fund	Class III	Return Before Taxes		10.29%	2.09%		8.65%	Jan. 29, 2002
Return Before Taxes Class IV, GMO International Core Equity Fund	Class IV	Return Before Taxes		10.34%	2.15%		9.14%	Jun. 30, 2003
Return Before Taxes Class VI, GMO International Core Equity Fund	Class VI	Return Before Taxes		10.39%			0.59%	Mar. 28, 2006
Return After Taxes on Distributions Class III, GMO International Core Equity Fund	Class III	Return After Taxes on Distributions		10.11%	1.28%		7.88%	Jan. 29, 2002
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO International Core Equity Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		7.28%	1.73%		7.50%	Jan. 29, 2002
MSCI EAFE Index Class III, GMO International Core Equity Fund	Class III	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%		7.41%	Jan. 29, 2002
MSCI EAFE Index Class IV, GMO International Core Equity Fund	Class IV	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%		9.32%	Jun. 30, 2003
MSCI EAFE Index Class VI, GMO International Core Equity Fund	Class VI	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%			0.82%	Mar. 28, 2006

GMO INTERNATIONAL INTRINSIC VALUE FUND

GMO INTERNATIONAL INTRINSIC VALUE FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO INTERNATIONAL INTRINSIC VALUE FUND		Class II, GMO International Intrinsic Value Fund	Class III, GMO International Intrinsic Value Fund	Class IV, GMO International Intrinsic Value Fund
Operating Expenses Column [Text]		Class II	Class III	Class IV
Management fee		0.50%	0.50%	0.50%
Shareholder service fee		0.22%	0.15%	0.09%
Other expenses		0.05%	0.05%	0.05%
Total annual operating expenses		0.77%	0.70%	0.64%
Expense reimbursement	[1]	(0.05%)	(0.05%)	(0.05%)
Total annual operating expenses after expense reimbursement		0.72%	0.65%	0.59%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL INTRINSIC VALUE FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class II, GMO International Intrinsic Value Fund	Class II	74	[1]	241	423	949
Class III, GMO International Intrinsic Value Fund	Class III	66	[1]	219	385	866
Class IV, GMO International Intrinsic Value Fund	Class IV	60	[1]	200	352	794

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After tax returns are shown for Class III Shares only; after tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 22.40% (2Q2009)

Lowest Quarter: -18.13% (3Q2008)

Year-to-Date (as of 3/31/11): 4.16%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL INTRINSIC VALUE FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class II, GMO International Intrinsic Value Fund	Class II	Return Before Taxes		7.53%	1.41%	6.73%	6.98%	Sep. 26, 1996
Return Before Taxes Class III, GMO International Intrinsic Value Fund	Class III	Return Before Taxes		7.59%	1.48%	6.80%	8.45%	Mar. 31, 1987
Return Before Taxes Class IV, GMO International Intrinsic Value Fund	Class IV	Return Before Taxes		7.61%	1.54%	6.88%	7.54%	Jan. 09, 1998
Return After Taxes on Distributions Class III, GMO International Intrinsic Value Fund	Class III	Return After Taxes on Distributions		7.58%	0.24%	5.72%	6.78%	Mar. 31, 1987
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO International Intrinsic Value Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		5.43%	1.36%	5.84%	6.78%	Mar. 31, 1987
MSCI EAFE Index Class II, GMO International Intrinsic Value Fund	Class II	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	4.67%	Sep. 26, 1996
MSCI EAFE Index Class III, GMO International Intrinsic Value Fund	Class III	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	5.31%	Mar. 31, 1987
MSCI EAFE Index Class IV, GMO International Intrinsic Value Fund	Class IV	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	5.05%	Jan. 09, 1998
MSCI EAFE Value Index (Fund benchmark) Class II, GMO International Intrinsic Value Fund	Class II	MSCI EAFE Value Index (Fund benchmark)	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	3.25%	1.37%	4.19%	5.80%	Sep. 26, 1996
MSCI EAFE Value Index (Fund benchmark) Class III, GMO International Intrinsic Value Fund	Class III	MSCI EAFE Value Index (Fund benchmark)	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	3.25%	1.37%	4.19%	7.27%	Mar. 31, 1987
MSCI EAFE Value Index (Fund benchmark) Class IV, GMO International Intrinsic Value Fund	Class IV	MSCI EAFE Value Index (Fund benchmark)	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	3.25%	1.37%	4.19%	6.26%	Jan. 09, 1998

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND

Investment Objective

High total return.

Fees and Expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO INTERNATIONAL LARGE/MID CAP VALUE FUND		Class III, GMO International Large/Mid Cap Value Fund	Class IV, GMO International Large/Mid Cap Value Fund	Class V, International Large/Mid Cap Value Fund	Class VI, GMO International Large/Mid Cap Value Fund
Operating Expenses Column [Text]		Class III	Class IV	Class V	Class VI
Management fee		0.50%	0.50%	0.50%	0.50%
Shareholder service fee		0.15%	0.09%	0.085%	0.055%
Other expenses	[1]	0.15%	0.15%	0.15%	0.15%
Total annual operating expenses	[1]	0.80%	0.74%	0.74%	0.71%
Expense reimbursement	[1][2]	(0.14%)	(0.14%)	(0.14%)	(0.14%)
Total annual operating expenses after expense reimbursement	[1]	0.66%	0.60%	0.60%	0.57%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL LARGE/MID CAP VALUE FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year	3 Years
Class III, GMO International Large/Mid Cap Value Fund	Class III	82	255
Class IV, GMO International Large/Mid Cap Value Fund	Class IV	76	237
Class V, International Large/Mid Cap Value Fund	Class V	76	237
Class VI, GMO International Large/Mid Cap Value Fund	Class VI	73	227

Portfolio Turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.

Principal Investment Strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. companies that issue stocks included in the MSCI Standard Indices, international stock indices, and in companies with similar market capitalizations (“large- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of large- and mid-cap companies (see “Name Policies”). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S. and include both developed and emerging countries. For purposes of the Fund’s investments, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal Risks of Investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO INTERNATIONAL GROWTH EQUITY FUND

GMO INTERNATIONAL GROWTH EQUITY FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO INTERNATIONAL GROWTH EQUITY FUND		Class III, GMO International Growth Equity Fund	Class IV, GMO International Growth Equity Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.50%	0.50%
Shareholder service fee		0.15%	0.09%
Other expenses		0.05%	0.05%
Total annual operating expenses		0.70%	0.64%
Expense reimbursement	[1]	(0.05%)	(0.05%)
Total annual operating expenses after expense reimbursement		0.65%	0.59%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL GROWTH EQUITY FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO International Growth Equity Fund	Class III	66	[1]	221	389	877
Class IV, GMO International Growth Equity Fund	Class IV	60	[1]	202	356	805

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 59% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[7]

Highest Quarter: 17.83% (3Q2010)

Lowest Quarter: -19.33% (3Q2008)

Year-to-Date (as of 3/31/11): 1.77%

Average Annual Total Returns Periods Ending December 31, 2010

^[7]

Average Annual Total Returns GMO INTERNATIONAL GROWTH EQUITY FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO International Growth Equity Fund	Class III	Return Before Taxes		14.02%	4.48%		8.02%	Nov. 30, 2001
Return Before Taxes Class IV, GMO International Growth Equity Fund	Class IV	Return Before Taxes		14.13%			3.28%	Jul. 12, 2006
Return After Taxes on Distributions Class III, GMO International Growth Equity Fund	Class III	Return After Taxes on Distributions		14.02%	2.88%		6.82%	Nov. 30, 2001
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO International Growth Equity Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		9.49%	3.55%		6.77%	Nov. 30, 2001
MSCI EAFE Index Class III, GMO International Growth Equity Fund	Class III	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%		6.73%	Nov. 30, 2001
MSCI EAFE Index Class IV, GMO International Growth Equity Fund	Class IV	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%			0.79%	Jul. 12, 2006
MSCI EAFE Growth Index (Fund benchmark) Class III, GMO International Growth Equity Fund	Class III	MSCI EAFE Growth Index (Fund benchmark)	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	12.25%	3.46%		6.28%	Nov. 30, 2001
MSCI EAFE Growth Index (Fund benchmark) Class IV, GMO International Growth Equity Fund	Class IV	MSCI EAFE Growth Index (Fund benchmark)	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	12.25%			2.07%	Jul. 12, 2006

GMO DEVELOPED WORLD STOCK FUND

GMO DEVELOPED WORLD STOCK FUND

Investment objective

High total return.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO DEVELOPED WORLD STOCK FUND		Class III, GMO Developed World Stock Fund	Class IV, GMO Developed World Stock Fund
Shareholder Fees Column [Text]		Class III	Class IV
Purchase premium (as a percentage of amount invested)	[1]	0.25%	0.25%
Redemption fee (as a percentage of amount redeemed)	[1]	0.25%	0.25%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO DEVELOPED WORLD STOCK FUND		Class III, GMO Developed World Stock Fund	Class IV, GMO Developed World Stock Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.45%	0.45%
Shareholder service fee		0.15%	0.10%
Other expenses		0.11%	0.11%
Total annual operating expenses		0.71%	0.66%
Expense reimbursement	[1]	(0.11%)	(0.11%)
Total annual operating expenses after expense reimbursement		0.60%	0.55%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO DEVELOPED WORLD STOCK FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Developed World Stock Fund USD ($)		Class III	112	[1]	269	439	933		Class III	86	[1]	240	408	895
Class IV, GMO Developed World Stock Fund USD ($)		Class IV	107	[1]	253	412	873		Class IV	81	[1]	225	381	835

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 34% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in stocks or groups of stocks that the Manager believes will provide higher returns than the MSCI World Index.

The Manager uses active investment management methods, which means that stocks are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting stocks for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify stocks that the Manager believes present positive return potential relative to other stocks. Some of these methods evaluate individual stocks or a group of stocks (e.g., stocks of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of a stock or a group of stocks. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of a stock or group of stocks relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in stocks, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in stocks tied economically to developed markets (see “Name Policies”). For this purpose, the term “stocks” refers to investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts, and the term “developed markets” refers to those countries included in the MSCI World Index, a global developed markets equity index, and countries with similar characteristics (e.g., countries that have sustained economic development, sufficient liquidity for listed companies and accessible markets). The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 18.37% (2Q2009)

Lowest Quarter: -19.92% (4Q2008)

Year-to-Date (as of 3/31/11): 4.62%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO DEVELOPED WORLD STOCK FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Developed World Stock Fund	Class III	Return Before Taxes		9.82%	1.78%		2.64%	Aug. 01, 2005
Return Before Taxes Class IV, GMO Developed World Stock Fund	Class IV	Return Before Taxes		9.93%	1.83%		2.51%	Sep. 01, 2005
Return After Taxes on Distributions Class III, GMO Developed World Stock Fund	Class III	Return After Taxes on Distributions		9.30%	0.85%		1.76%	Aug. 01, 2005
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Developed World Stock Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.64%	1.31%		2.06%	Aug. 01, 2005
MSCI World Index Class III, GMO Developed World Stock Fund	Class III	MSCI World Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%	2.43%		3.38%	Aug. 01, 2005
MSCI World Index Class IV, GMO Developed World Stock Fund	Class IV	MSCI World Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%	2.43%		3.17%	Sep. 01, 2005

GMO INTERNATIONAL SMALL COMPANIES FUND

GMO INTERNATIONAL SMALL COMPANIES FUND

Investment objective

High total return.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO INTERNATIONAL SMALL COMPANIES FUND Class III, GMO International Small Companies Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO INTERNATIONAL SMALL COMPANIES FUND Class III, GMO International Small Companies Fund
Operating Expenses Column [Text]		Class III
Management fee		0.60%
Shareholder service fee		0.15%
Other expenses	[1]	0.13%
Total annual operating expenses		0.88%
Expense reimbursement	[2]	(0.13%)
Total annual operating expenses after expense reimbursement		0.75%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL SMALL COMPANIES FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO International Small Companies Fund USD ($)		Class III	178	[1]	373	583	1,192		Class III	126	[1]	316	523	1,117

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Small Cap Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. small companies. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies (see “Name Policies”). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S., and include both developed and emerging companies (“Non-U.S. Companies”). The Manager considers “small companies” to be all Non-U.S. Companies other than (i) the largest 500 companies in developed countries based on full, non-float adjusted market capitalization and (ii) any company in an emerging country with a full, non-float adjusted market capitalization that is greater than or equal to that of the smallest excluded developed country companies. A company’s full, non-float adjusted market capitalization includes all of the company’s outstanding equity securities. As of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company included within the Fund’s definition of small companies was approximately $8.3 billion. For purposes of the Fund’s investments, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 32.07% (2Q2009)

Lowest Quarter: -21.15% (3Q2008)

Year-to-Date (as of 3/31/11): 1.71%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL SMALL COMPANIES FUND Class III, GMO International Small Companies Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		19.97%	4.81%	11.94%	9.83%	Oct. 14, 1991
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		19.52%	1.91%	9.08%	7.53%	Oct. 14, 1991
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		13.01%	3.46%	9.78%	7.86%	Oct. 14, 1991
MSCI EAFE Small Cap Index (Fund benchmark)	Class III	MSCI EAFE Small Cap Index (Fund benchmark)	(returns reflect no deductions for fees or expenses, but are net of withholding tax on dividend reinvestments)	22.04%	2.81%	9.45%		Oct. 14, 1991
MSCI EAFE Small Cap + Index (Composite index)	Class III	MSCI EAFE Small Cap + Index (Composite index)		22.04%	5.70%	9.56%	7.20%	Oct. 14, 1991

GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND

GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND

Investment Objective

High total return.

Fees and Expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees	GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND Class III, GMO Asset Allocation International Small Companies Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND Class III, GMO Asset Allocation International Small Companies Fund
Operating Expenses Column [Text]		Class III
Management fee		0.60%
Shareholder service fee		0.15%
Other expenses	[1]	0.14%
Total annual operating expenses	[1]	0.89%
Expense reimbursement	[1][2]	(0.14%)
Total annual operating expenses after expense reimbursement	[1]	0.75%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year	3 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year	3 Years
GMO Trust	If you sell your shares				If you do not sell your shares
Class III, GMO Asset Allocation International Small Companies Fund USD ($)		Class III	192	389		Class III	140	332

Portfolio Turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund's portfolio turnover rate is not available.

Principal Investment Strategies

The Manager pursues the Fund's investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund's strategic direction.

The Manager typically seeks to achieve the Fund's investment objective by investing in equities or groups of equities of non-U.S. small companies.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter ("OTC") derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. small companies. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies (see "Name Policies"). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S., and include both developed and emerging companies ("Non-U.S. Companies"). The Manager considers “small companies” to be all Non-U.S. Companies other than (i) the largest 500 companies in developed countries based on full, non-float adjusted market capitalization and (ii) any company in an emerging country with a full, non-float adjusted market capitalization that is greater than or equal to that of the smallest excluded developed country companies. A company's full, non-float adjusted market capitalization includes all of the company's outstanding equity securities. As of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company included within the Fund's definition of small companies was approximately $8.3 billion. For purposes of the Fund's investments, the term "equities" refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal Risks of Investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND

Investment objective

High after-tax total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND Class III, GMO Tax-Managed International Equities Fund
Operating Expenses Column [Text]		Class III
Management fee		0.50%
Shareholder service fee		0.15%
Other expenses		0.11%
Total annual operating expenses		0.76%
Expense reimbursement	[1]	(0.11%)
Total annual operating expenses after expense reimbursement		0.65%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND Class III, GMO Tax-Managed International Equities Fund	Class III	66	[1]	232	412	932

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Index (after tax).

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

The Manager considers the tax effects of a proposed trade in conjunction with the return forecast of the identified equities, and their potential contribution to the overall portfolio. The Manager also may consider the Fund’s realized and unrealized gains and losses, and current market conditions, because these factors also influence the decision to buy or sell securities.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries. These investments generally will represent 15% or less of the Fund’s total assets.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. There can be no assurance that the Fund’s tax management strategies will be effective, and you may incur tax liabilities that exceed your economic return. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is computed by the Manager) and a broad-based international stock index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares (Before Tax) Years Ending December 31

Highest Quarter: 21.51% (2Q2009)

Lowest Quarter: -20.34% (3Q2008)

Year-to-Date (as of 3/31/11): 4.05%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND Class III, GMO Tax-Managed International Equities Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		9.49%	2.76%	7.67%	7.10%	Jul. 29, 1998
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		9.30%	1.99%	6.98%	6.47%	Jul. 29, 1998
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.82%	2.57%	6.76%	6.24%	Jul. 29, 1998
MSCI EAFE Index (after tax) (Fund benchmark)	Class III	MSCI EAFE Index (after tax) (Fund benchmark)	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	6.85%	1.55%	2.88%	3.05%	Jul. 29, 1998
MSCI EAFE Index	Class III	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	3.74%	Jul. 29, 1998

GMO FOREIGN FUND

GMO FOREIGN FUND

Investment objective

Total return in excess of that of its benchmark, the MSCI EAFE Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO FOREIGN FUND		Class II, GMO Foreign Fund	Class III, GMO Foreign Fund	Class IV, GMO Foreign Fund
Operating Expenses Column [Text]		Class II	Class III	Class IV
Management fee		0.60%	0.60%	0.60%
Shareholder service fee		0.22%	0.15%	0.09%
Other expenses		0.06%	0.06%	0.06%
Total annual operating expenses		0.88%	0.81%	0.75%
Expense reimbursement	[1]	(0.06%)	(0.06%)	(0.06%)
Total annual operating expenses after expense reimbursement		0.82%	0.75%	0.69%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO FOREIGN FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class II, GMO Foreign Fund	Class II	84	[1]	275	482	1,079
Class III, GMO Foreign Fund	Class III	77	[1]	253	444	996
Class IV, GMO Foreign Fund	Class IV	70	[1]	234	411	925

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to non-U.S. countries, including companies that issue equity investments included in the MSCI international developed country universe (the universe of securities from which the MSCI EAFE Index, a developed markets index, is constructed) and companies whose equity investments are traded in the securities markets of the world’s non-developed countries (“emerging countries”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to countries outside the U.S. (see “Name Policies”).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Information on the Fund’s return after taxes is unavailable prior to June 28, 1996, the date the Fund commenced operations as a registered investment company. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 21.67% (2Q2009)

Lowest Quarter: -19.12% (3Q2008)

Year-to-Date (as of 3/31/11): 3.95%

Average Annual Total Returns Periods Ending December 31, 2010

^[8]

Average Annual Total Returns GMO FOREIGN FUND	Column		Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.		Inception Date
Return Before Taxes Class II, GMO Foreign Fund	Class II		Return Before Taxes		4.62%	1.51%	5.92%	7.45%		Sep. 30, 1996
Return Before Taxes Class III, GMO Foreign Fund	Class III	[1]	Return Before Taxes		4.77%	1.60%	6.00%	12.68%		Aug. 31, 1984
Return Before Taxes Class IV, GMO Foreign Fund	Class IV		Return Before Taxes		4.82%	1.63%	6.06%	7.42%		Jan. 09, 1998
Return After Taxes on Distributions Class III, GMO Foreign Fund	Class III	[1]	Return After Taxes on Distributions		4.58%	0.62%	5.16%		[2]	Aug. 31, 1984
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Foreign Fund	Class III	[1]	Return After Taxes on Distributions and Sale of Fund Shares		3.60%	1.46%	5.22%		[2]	Aug. 31, 1984
MSCI EAFE Index Class II, GMO Foreign Fund	Class II		MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	4.64%		Sep. 30, 1996
MSCI EAFE Index Class III, GMO Foreign Fund	Class III	[1]	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	9.76%		Aug. 31, 1984
MSCI EAFE Index Class IV, GMO Foreign Fund	Class IV		MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	5.05%		Jan. 09, 1998

GMO FOREIGN SMALL COMPANIES FUND

GMO FOREIGN SMALL COMPANIES FUND

Investment objective

Total return in excess of that of its benchmark, the S&P Developed ex-U.S. Small Cap Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO FOREIGN SMALL COMPANIES FUND	Class III, GMO Foreign Small Companies Fund	Class IV, GMO Foreign Small Companies Fund
Shareholder Fees Column [Text]	Class III	Class IV
Purchase premium (as a percentage of amount invested)	0.50%	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%	0.50%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO FOREIGN SMALL COMPANIES FUND		Class III, GMO Foreign Small Companies Fund	Class IV, GMO Foreign Small Companies Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.70%	0.70%
Shareholder service fee		0.15%	0.10%
Other expenses		0.14%	0.14%
Total annual operating expenses		0.99%	0.94%
Expense reimbursement	[1]	(0.14%)	(0.14%)
Total annual operating expenses after expense reimbursement		0.85%	0.80%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO FOREIGN SMALL COMPANIES FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Foreign Small Companies Fund USD ($)		Class III	188	[1]	406	641	1,318		Class III	136	[1]	350	581	1,244
Class IV, GMO Foreign Small Companies Fund USD ($)		Class IV	183	[1]	390	615	1,260		Class IV	131	[1]	334	554	1,186

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to countries other than the U.S. whose outstanding publicly traded equities are in the lowest 25% of available market capitalization (float) in a particular country (“small companies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies that are tied economically to countries outside the U.S. (see “Name Policies”). The market capitalization range of companies whose equity investments are held by the Fund is generally within the market capitalization range of companies in the Fund’s benchmark, which represents the lowest 15% of available market capitalization (float) of the S&P Broad Market Index in each country. Depending on the country, as of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company (in a particular country) included in the S&P Developed ex-U.S. Small Cap Index ranged from approximately $563 million (Greece) to $15.8 billion (Germany). Depending upon the country, as of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company (in a particular country) included within the Fund’s definition of small companies ranged from approximately $772 million (Greece) to $22 billion (Switzerland) (based on exchange rates as of May 31, 2011).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments (excluding investments in companies tied economically to emerging countries included in the Fund’s benchmark) generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III, tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 31.25% (2Q2009)

Lowest Quarter: -24.05% (3Q2008)

Year-to-Date (as of 3/31/11): 3.94%

Average Annual Total Returns Periods Ending December 31, 2010

^[9]

Average Annual Total Returns GMO FOREIGN SMALL COMPANIES FUND	Column		Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.		Inception Date
Return Before Taxes Class III, GMO Foreign Small Companies Fund	Class III	[1]	Return Before Taxes		23.59%	7.69%	13.59%	12.09%		Jan. 04, 1995
Return Before Taxes Class IV, GMO Foreign Small Companies Fund	Class IV	[2]	Return Before Taxes		23.67%	7.71%		13.93%		Jun. 14, 2002
Return After Taxes on Distributions Class III, GMO Foreign Small Companies Fund	Class III	[1]	Return After Taxes on Distributions		23.58%	5.66%	11.92%		[3]	Jan. 04, 1995
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Foreign Small Companies Fund	Class III	[1]	Return After Taxes on Distributions and Sale of Fund Shares		15.29%	6.21%	11.75%		[3]	Jan. 04, 1995
S&P Developed ex-U.S. Small Cap Index Class III, GMO Foreign Small Companies Fund	Class III	[1]	S&P Developed ex-U.S. Small Cap Index	(reflects no deduction for fees, expenses, or taxes)	21.96%	5.16%	9.28%	7.39%		Jan. 04, 1995
S&P Developed ex-U.S. Small Cap Index Class IV, GMO Foreign Small Companies Fund	Class IV	[2]	S&P Developed ex-U.S. Small Cap Index	(reflects no deduction for fees, expenses, or taxes)	21.96%	5.16%		12.28%		Jun. 14, 2002

GMO EMERGING MARKETS FUND

GMO EMERGING MARKETS FUND

Investment objective

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO EMERGING MARKETS FUND	Class II, GMO Emerging Markets Fund		Class III, GMO Emerging Markets Fund		Class IV, GMO Emerging Markets Fund		Class V, GMO Emerging Markets Fund	Class VI, GMO Emerging Markets Fund
Shareholder Fees Column [Text]	Class II		Class III		Class IV		Class V	Class VI
Purchase premium (as a percentage of amount invested)	0.80%		0.80%		0.80%		0.80%	0.80%
Redemption fee (as a percentage of amount redeemed)	0.80%	[1]	0.80%	[1]	0.80%	[1]	0.80%	0.80%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO EMERGING MARKETS FUND		Class II, GMO Emerging Markets Fund	Class III, GMO Emerging Markets Fund	Class IV, GMO Emerging Markets Fund	Class V, GMO Emerging Markets Fund	Class VI, GMO Emerging Markets Fund
Operating Expenses Column [Text]		Class II	Class III	Class IV	Class V	Class VI
Management fee		0.75%	0.75%	0.75%	0.75%	0.75%
Shareholder service fee		0.22%	0.15%	0.105%	0.085%	0.055%
Other expenses		0.13%	0.13%	0.13%	0.13%	0.13%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.01%	0.01%	0.01%	0.01%	0.01%
Total annual operating expenses		1.11%	1.04%	1.00%	0.98%	0.95%
Expense reimbursement	[2]	(0.03%)	(0.01%)	(0.01%)	(0.04%)	(0.04%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		1.08%	1.03%	0.99%	0.94%	0.91%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO EMERGING MARKETS FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class II, GMO Emerging Markets Fund USD ($)		Class II	272	[1]	516	780	1,534		Class II	189	[1]	427	684	1,418
Class III, GMO Emerging Markets Fund USD ($)		Class III	267	[1]	496	745	1,457		Class III	184	[1]	407	648	1,340
Class IV, GMO Emerging Markets Fund USD ($)		Class IV	263	[1]	484	724	1,411		Class IV	180	[1]	395	627	1,294
Class V, GMO Emerging Markets Fund USD ($)		Class V	258	[1]	475	710	1,386		Class V	175	[1]	386	613	1,268
Class VI, GMO Emerging Markets Fund USD ($)		Class VI	255	[1]	466	694	1,352		Class VI	172	[1]	376	597	1,233

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 114% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging markets. “Emerging markets” include all markets that are not treated as “developed markets” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging markets (see “Name Policies”). In addition to investing in companies tied economically to emerging markets, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging markets, the economies of which tend to be more volatile than the economies of developed markets.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 31.90% (2Q2009)

Lowest Quarter: -30.50% (4Q2008)

Year-to-Date (as of 3/31/11): 4.49%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO EMERGING MARKETS FUND	Column		Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class II, GMO Emerging Markets Fund	Class II	[1]	Return Before Taxes		18.55%	9.91%	18.18%	11.80%	Nov. 29, 1996
Return Before Taxes Class III, GMO Emerging Markets Fund	Class III		Return Before Taxes		18.59%	9.98%	18.28%	10.60%	Dec. 09, 1993
Return Before Taxes Class IV, GMO Emerging Markets Fund	Class IV		Return Before Taxes		18.67%	10.03%	18.33%	13.92%	Jan. 09, 1998
Return Before Taxes Class V, GMO Emerging Markets Fund	Class V	[2]	Return Before Taxes		18.78%	10.07%		20.37%	Aug. 04, 2003
Return Before Taxes Class VI, GMO Emerging Markets Fund	Class VI		Return Before Taxes		18.77%	10.10%		20.77%	Jun. 30, 2003
Return After Taxes on Distributions Class III, GMO Emerging Markets Fund	Class III		Return After Taxes on Distributions		18.69%	7.30%	16.21%	9.00%	Dec. 09, 1993
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Emerging Markets Fund	Class III		Return After Taxes on Distributions and Sale of Fund Shares		12.01%	8.15%	16.06%	8.96%	Dec. 09, 1993
S&P/IFCI Composite Index Class II, GMO Emerging Markets Fund	Class II	[1]	S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%	17.68%	10.11%	Nov. 29, 1996
S&P/IFCI Composite Index Class III, GMO Emerging Markets Fund	Class III		S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%	17.68%	8.12%	Dec. 09, 1993
S&P/IFCI Composite Index Class IV, GMO Emerging Markets Fund	Class IV		S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%	17.68%	13.29%	Jan. 09, 1998
S&P/IFCI Composite Index Class V, GMO Emerging Markets Fund	Class V	[2]	S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%		21.47%	Aug. 04, 2003
S&P/IFCI Composite Index Class VI, GMO Emerging Markets Fund	Class VI		S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%		22.03%	Jun. 30, 2003

GMO EMERGING COUNTRIES FUND

GMO EMERGING COUNTRIES FUND

Investment objective

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO EMERGING COUNTRIES FUND Class III, GMO Emerging Countries Fund
Operating Expenses Column [Text]		Class III
Management fee		0.65%
Shareholder service fee		0.15%
Other expenses		0.50%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.02%
Total annual operating expenses		1.32%
Expense reimbursement	[2]	(0.15%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		1.17%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO EMERGING COUNTRIES FUND Class III, GMO Emerging Countries Fund	Class III	119	[1]	404	709	1,577

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 124% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging countries. “Emerging countries” include all countries that are not treated as “developed market countries” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging countries (see “Name Policies”). In addition to investing in companies tied economically to emerging countries, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 31.14% (2Q2009)

Lowest Quarter: -31.38% (4Q2008)

Year-to-Date (as of 3/31/11): 4.63%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO EMERGING COUNTRIES FUND Class III, GMO Emerging Countries Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		20.47%	10.23%	17.59%	11.64%	Aug. 29, 1997
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		20.59%	7.33%	15.28%	9.85%	Aug. 29, 1997
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		13.88%	8.44%	15.35%	9.97%	Aug. 29, 1997
S&P/IFCI Composite Index	Class III	S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%	17.68%	10.48%	Aug. 29, 1997

GMO EMERGING DOMESTIC OPPORTUNITIES FUND

GMO EMERGING DOMESTIC OPPORTUNITIES FUND

Investment objective

Total return.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO EMERGING DOMESTIC OPPORTUNITIES FUND	Class II, GMO Emerging Domestic Opportunities Fund	Class III, GMO Emerging Domestic Opportunities Fund	Class IV, GMO Emerging Domestic Opportunities Fund	Class V, GMO Emerging Domestic Opportunities Fund	Class VI, GMO Emerging Domestic Opportunities Fund
Shareholder Fees Column [Text]	Class II	Class III	Class IV	Class V	Class VI
Purchase premium (as a percentage of amount invested)	0.80%	0.80%	0.80%	0.80%	0.80%
Redemption fee (as a percentage of amount redeemed)	0.80%	0.80%	0.80%	0.80%	0.80%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO EMERGING DOMESTIC OPPORTUNITIES FUND		Class II, GMO Emerging Domestic Opportunities Fund	Class III, GMO Emerging Domestic Opportunities Fund	Class IV, GMO Emerging Domestic Opportunities Fund	Class V, GMO Emerging Domestic Opportunities Fund	Class VI, GMO Emerging Domestic Opportunities Fund
Operating Expenses Column [Text]		Class II	Class III	Class IV	Class V	Class VI
Management fee		0.75%	0.75%	0.75%	0.75%	0.75%
Shareholder service fee		0.22%	0.15%	0.105%	0.085%	0.055%
Other expenses	[1]	3.55%	3.55%	3.55%	3.55%	3.55%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.01%	0.01%	0.01%	0.01%	0.01%
Total annual operating expenses	[1]	4.53%	4.46%	4.42%	4.40%	4.37%
Expense reimbursement	[1][2]	(3.45%)	(3.45%)	(3.45%)	(3.45%)	(3.45%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)	[1]	1.08%	1.01%	0.97%	0.95%	0.92%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO EMERGING DOMESTIC OPPORTUNITIES FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year	3 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year	3 Years
GMO Trust	If you sell your shares				If you do not sell your shares
Class II, GMO Emerging Domestic Opportunities Fund USD ($)		Class II	610	1,518		Class II	530	1,438
Class III, GMO Emerging Domestic Opportunities Fund USD ($)		Class III	603	1,499		Class III	524	1,418
Class IV, GMO Emerging Domestic Opportunities Fund USD ($)		Class IV	600	1,488		Class IV	520	1,407
Class V, GMO Emerging Domestic Opportunities Fund USD ($)		Class V	598	1,482		Class V	518	1,401
Class VI, GMO Emerging Domestic Opportunities Fund USD ($)		Class VI	596	1,474		Class VI	515	1,393

Portfolio Turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund had not commenced operations as of the fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate is not available.

Principal Investment Strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies whose prospects are linked to the internal (“domestic”) development and growth of the world's non-developed markets (“emerging markets”), including companies that provide goods and services to emerging market consumers. “Emerging markets” include all markets that are not treated as “developed markets” in the MSCI World Index or MSCI EAFE Index.

The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments related to emerging markets (see “Name Policy”). The Fund’s investments are not limited to investments in companies located in any particular country or geographic region, and may include investments in companies located in developed markets (e.g., the U.S.) that are related to, or whose prospects are linked to, emerging markets. The Fund does not control risk relative to the MSCI Emerging Markets (EM) Index or any other securities index.

The Manager uses fundamental analysis to evaluate and select countries, sectors and companies that it believes are most likely to benefit from domestic growth in emerging markets. In evaluating and selecting investments, the Manager may consider many factors, including the Manager’s assessment of a country’s and/or sector’s fundamentals or growth prospects as well as a company’s positioning relative to its competitors.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal Risks of Investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments related to emerging markets, the economies of which tend to be more volatile than the economies of developed markets.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – The Fund’s investments in companies whose prospects are linked to the internal development and growth of emerging markets create additional risk because the performance of those companies is likely to be highly correlated.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security.

The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations. The Fund is also subject to risk because the Fund does not seek to control risk relative to a particular securities market index or benchmark.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

Performance

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO TAIWAN FUND

GMO TAIWAN FUND

Investment objective

Total return in excess of that of its benchmark, the MSCI Taiwan Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO TAIWAN FUND Class III, GMO Taiwan Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.15%
Redemption fee (as a percentage of amount redeemed)	0.45%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO TAIWAN FUND Class III, GMO Taiwan Fund
Operating Expenses Column [Text]		Class III
Management fee		0.81%
Shareholder service fee		0.15%
Other expenses		0.37%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.02%
Total annual fund operating expenses (Fund and underlying fund expenses)		1.35%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO TAIWAN FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Taiwan Fund USD ($)		Class III	199	[1]	492	807	1,701		Class III	152	[1]	442	753	1,636

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 129% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies doing business in, or otherwise tied economically to, Taiwan. The Fund may invest in companies of any market capitalization. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to Taiwan (see “Name Policies”).

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select sectors and equity investments. In evaluating and selecting investments, the Manager may consider many factors, including the Manager’s assessment of a sector’s fundamentals as well as a company’s positioning relative to its competitors.

The Fund may invest a significant portion of its assets in securities of issuers in industries with high positive correlations to one another (e.g., different industries within broad sectors, such as technology or financial services).

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries. Certain characteristics of Taiwan’s economy and geographic location also subject the Fund to risks. For example, Taiwan is a small island state with few raw material resources and limited land area and thus it relies heavily on imports for its commodity needs. Any fluctuations or shortages in the commodity markets could have a negative impact on the Taiwanese economy. Also, rising labor costs and increasing environmental consciousness have led some labor-intensive industries to relocate to countries with cheaper work forces, and continued labor outsourcing may adversely affect the Taiwanese economy. Taiwan’s economy also is intricately linked with economies of other Asian countries, which, like emerging market economies, often experience over-extensions of credit, frequent and pronounced currency fluctuations, devaluations and restrictions, rising unemployment and fluctuations in inflation. Currency devaluations in any one country can have a significant effect on the entire region. Political and social unrest in Asian countries could cause further economic and market uncertainty in Taiwan. In particular, the Taiwanese economy is dependent on the economies of Japan and China, and also the United States, and a reduction in purchases by any of them of Taiwanese products and services or negative changes in their economies would likely have an adverse impact on the Taiwanese economy. Taiwan’s geographic proximity to the People’s Republic of China and Taiwan’s history of political contention with China have resulted in ongoing tensions with China, including the continual risk of war with China. These tensions may materially affect the Taiwanese economy and securities markets. All of these risks could reduce the value of an investment in Taiwan Fund.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments tied economically to Taiwan, creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 22.85% (3Q2010)

Lowest Quarter: -23.74% (4Q2008)

Year-to-Date (as of 3/31/11): -0.04%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO TAIWAN FUND Class III, GMO Taiwan Fund	Column	Label		Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Inception	Inception Date
Return Before Taxes	Class III	Return Before Taxes			24.09%	8.44%		11.12%	Oct. 04, 2002
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions	[1]		23.80%	6.56%		9.72%	Oct. 04, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares	[1]		15.76%	6.82%		9.47%	Oct. 04, 2002
MSCI Taiwan Index	Class III	MSCI Taiwan Index		(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	21.84%	8.74%		13.15%	Oct. 04, 2002

GMO FLEXIBLE EQUITIES FUND

GMO FLEXIBLE EQUITIES FUND

Investment objective

Total return in excess of that of its benchmark, the MSCI World Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO FLEXIBLE EQUITIES FUND		Class III, GMO Flexible Equities Fund	Class VI, GMO Flexible Equities Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.55%	0.55%
Shareholder service fee		0.15%	0.055%
Other expenses		0.11%	0.11%
Total annual operating expenses		0.81%	0.72%
Expense reimbursement	[1]	(0.11%)	(0.11%)
Total annual operating expenses after expense reimbursement		0.70%	0.61%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO FLEXIBLE EQUITIES FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Flexible Equities Fund	Class III	72	[1]	248	439	991
Class VI, GMO Flexible Equities Fund	Class VI	62	[1]	219	390	884

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 71% of the average value of its portfolio.

Principal investment strategies

The Fund may invest directly and indirectly (e.g., through underlying funds or derivatives) in equity investments traded in any of the world’s securities markets. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Fund is permitted to make equity investments of all types, including equity investments issued by foreign and/or U.S. companies, growth and/or value style equities, and equity investments of companies of any market capitalization. In addition, the Fund is not limited in how much it may invest in any market or in the types of equity investments it may pursue, and it may often invest all its assets in a limited number of equity investments of companies in a single country and/or capitalization range. The Fund could experience material losses from a single investment. As of the date of this Prospectus, substantially all of the Fund’s assets were invested in equity investments tied economically to Japan.

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ significantly from the currency exposure represented by its equity investments. For investment and hedging purposes, the Fund also may make short sales of securities, including short sales of securities the Fund does not own. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

The Fund may identify and measure its performance against one or more secondary benchmarks from time to time. The Fund does not seek to control risk relative to the MSCI World Index or any other benchmark.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk. As noted above, as of the date of this Prospectus, substantially all of the Fund’s assets were invested in equity investments tied economically to Japan.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that the Fund’s loss on a short sale of securities that the Fund does not own is unlimited.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 20.74% (2Q2009)

Lowest Quarter: -24.04% (1Q2009)

Year-to-Date (as of 3/31/11): -0.65%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO FLEXIBLE EQUITIES FUND	Column	Label		Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Flexible Equities Fund	Class III	Return Before Taxes			2.22%			(1.66%)	Dec. 12, 2008
Return Before Taxes Class VI, GMO Flexible Equities Fund	Class VI	Return Before Taxes			2.27%			(1.56%)	Dec. 12, 2008
Return After Taxes on Distributions Class III, GMO Flexible Equities Fund	Class III	Return After Taxes on Distributions	[1]		2.13%			(1.88%)	Dec. 12, 2008
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Flexible Equities Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares	[1]		1.81%			(1.37%)	Dec. 12, 2008
MSCI World Index Class III, GMO Flexible Equities Fund	Class III	MSCI World Index		(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%			22.29%	Dec. 12, 2008
MSCI World Index Class VI, GMO Flexible Equities Fund	Class VI	MSCI World Index		(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%			22.29%	Dec. 12, 2008

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND

Investment objective

Total return greater than that of its benchmark, the MSCI EAFE Index (Hedged).

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND Class III, GMO Currency Hedged International Equity Fund
Operating Expenses Column [Text]		Class III
Management fee		0.54%
Shareholder service fee	[1]	0.15%
Other expenses		0.08%
Acquired fund fees and expenses (underlying fund expenses)		0.58%
Total annual operating expenses		1.35%
Expense reimbursement/waiver	[1]	(0.65%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.70%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND Class III, GMO Currency Hedged International Equity Fund	Class III	72	[1]	374	699	1,619

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in other GMO Funds. The Fund may invest in International Core Equity Fund, International Intrinsic Value Fund, International Growth Equity Fund, International Small Companies Fund and Flexible Equities Fund (collectively, the “underlying Funds”). In addition, the Fund may invest in securities directly. Under normal circumstances, the Fund invests directly and indirectly (through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among major sectors in the international equity markets (e.g., large-cap value, large-cap growth, large-cap core, small- and mid-cap value and small- and mid-cap growth) to select the underlying Funds and decide how much to invest in each. The Manager shifts investments among the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments.

The Manager assesses the currency exposure of the underlying Funds’ holdings and then attempts to hedge at least 70% of that exposure relative to the U.S. dollar through the use of currency forwards and other derivatives. While the Fund’s benchmark is fully hedged, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds. The Fund also may lend its portfolio securities.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund’s or the underlying Fund’s performance more than if the Fund or underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund or an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund or an underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests will not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged by the Fund or an underlying Fund.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The use of derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 16.08% (2Q2003)

Lowest Quarter: -15.63% (3Q2002)

Year-to-Date (as of 3/31/11): 0.43%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND Class III, GMO Currency Hedged International Equity Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		7.72%	0.81%	4.10%	7.65%	Jun. 30, 1995
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		7.72%	(2.90%)	0.90%	3.56%	Jun. 30, 1995
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		5.02%	3.99%	4.46%	6.06%	Jun. 30, 1995
MSCI EAFE Index (Hedged) (Fund benchmark)	Class III	MSCI EAFE Index (Hedged) (Fund benchmark)	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	5.60%	0.07%	0.59%	5.97%	Jun. 30, 1995
MSCI EAFE Index	Class III	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%	3.50%	5.09%	Jun. 30, 1995

GMO DOMESTIC BOND FUND

GMO DOMESTIC BOND FUND

Investment objective

Total return in excess of that of its benchmark, the Barclays Capital U.S. Government Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO DOMESTIC BOND FUND		Class III, GMO Domestic Bond Fund	Class VI, GMO Domestic Bond Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee	[1]	0.10%	0.10%
Shareholder service fee	[1]	0.15%	0.055%
Other expenses		0.03%	0.03%
Acquired fund fees and expenses (underlying fund expenses)	[2]	0.01%	0.01%
Total annual operating expenses		0.29%	0.20%
Expense reimbursement/waiver	[1]	(0.03%)	(0.03%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.26%	0.17%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO DOMESTIC BOND FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Domestic Bond Fund	Class III	27	[1]	95	169	388
Class VI, GMO Domestic Bond Fund	Class VI	17	[1]	64	114	264

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 8% of the average value of its portfolio.

Principal investment strategies

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

Historically, the Fund has implemented its strategies: (i) synthetically by using exchange-traded and over-the-counter (“OTC”) derivatives and investing in other GMO Funds and/or (ii) directly by purchasing bonds. The Fund principally holds shares of Short-Duration Collateral Fund (“SDCF”) (a Fund that primarily holds U.S. asset-backed securities).

The Fund has also invested in and may continue to hold:

• U.S. bonds (including U.S. government bonds, U.S. corporate bonds and asset-backed securities);

• derivatives, including without limitation, futures contracts, reverse repurchase agreements, credit default swaps and other swap contracts;

• shares of U.S. Treasury Fund (for cash management purposes); and

• foreign bonds.

Because of the deterioration in credit markets that became acute in 2008, the Fund, including through its investment in SDCF, currently has and is expected to continue to have material exposure to below investment grade U.S. asset-backed securities (also known as “junk bonds”). The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds tied economically to the U.S. (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 7.29% (3Q2009)

Lowest Quarter: -6.39% (4Q2008)

Year-to-Date (as of 3/31/11): 1.51%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO DOMESTIC BOND FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Domestic Bond Fund	Class III	Return Before Taxes		9.06%	5.39%	5.71%	6.54%	Aug. 18, 1994
Return Before Taxes Class VI, GMO Domestic Bond Fund	Class VI	Return Before Taxes		9.14%	5.47%		5.18%	Jul. 26, 2005
Return After Taxes on Distributions Class III, GMO Domestic Bond Fund	Class III	Return After Taxes on Distributions		8.64%	3.52%	3.78%	4.13%	Aug. 18, 1994
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Domestic Bond Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		5.88%	3.51%	3.63%	4.14%	Aug. 18, 1994
Barclays Capital U.S. Government Index Class III, GMO Domestic Bond Fund	Class III	Barclays Capital U.S. Government Index	(reflects no deduction for fees, expenses, or taxes)	5.52%	5.45%	5.42%	6.34%	Aug. 18, 1994
Barclays Capital U.S. Government Index Class VI, GMO Domestic Bond Fund	Class VI	Barclays Capital U.S. Government Index	(reflects no deduction for fees, expenses, or taxes)	5.52%	5.45%		5.16%	Jul. 26, 2005

GMO CORE PLUS BOND FUND

GMO CORE PLUS BOND FUND

Investment objective

Total return in excess of that of its benchmark, the Barclays Capital U.S. Aggregate Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO CORE PLUS BOND FUND		Class III, GMO Core Plus Bond Fund	Class IV, GMO Core Plus Bond Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.25%	0.25%
Shareholder service fee	[1]	0.15%	0.10%
Other expenses	[2]	0.13%	0.13%
Acquired fund fees and expenses (underlying fund expenses)	[3]	0.04%	0.04%
Total annual operating expenses		0.57%	0.52%
Expense reimbursement/waiver	[1]	(0.14%)	(0.14%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.43%	0.38%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO CORE PLUS BOND FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Core Plus Bond Fund	Class III	44	[1]	173	313	723
Class IV, GMO Core Plus Bond Fund	Class IV	39	[1]	157	286	662

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 46% of the average value of its portfolio.

Principal investment strategies

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 5.2 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy.

Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 9.12% (3Q2009)

Lowest Quarter: -15.24% (4Q2008)

Year-to-Date (as of 3/31/11): 1.54%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO CORE PLUS BOND FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Core Plus Bond Fund	Class III	Return Before Taxes		13.27%	2.91%	5.14%	5.62%	Apr. 30, 1997
Return Before Taxes Class IV, GMO Core Plus Bond Fund	Class IV	Return Before Taxes		13.31%	2.93%		3.08%	Jul. 26, 2005
Return After Taxes on Distributions Class III, GMO Core Plus Bond Fund	Class III	Return After Taxes on Distributions		10.56%	(0.60%)	2.19%	2.75%	Apr. 30, 1997
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Core Plus Bond Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		8.62%	0.36%	2.62%	3.08%	Apr. 30, 1997
Barclays Capital U.S. Aggregate Index Class III, GMO Core Plus Bond Fund	Class III	Barclays Capital U.S. Aggregate Index	(reflects no deduction for fees, expenses, or taxes)	6.54%	5.80%	5.84%	6.30%	Apr. 30, 1997
Barclays Capital U.S. Aggregate Index Class IV, GMO Core Plus Bond Fund	Class IV	Barclays Capital U.S. Aggregate Index	(reflects no deduction for fees, expenses, or taxes)	6.54%	5.80%		5.46%	Jul. 26, 2005

GMO INTERNATIONAL BOND FUND

GMO INTERNATIONAL BOND FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO INTERNATIONAL BOND FUND Class III, GMO International Bond Fund
Operating Expenses Column [Text]		Class III
Management fee		0.25%
Shareholder service fee	[1]	0.15%
Other expenses	[2]	0.21%
Acquired fund fees and expenses (underlying fund expenses)	[3]	0.07%
Total annual operating expenses		0.68%
Expense reimbursement/waiver	[1]	(0.22%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.46%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO INTERNATIONAL BOND FUND Class III, GMO International Bond Fund	Class III	47	[1]	200	366	848

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 46% of the average value of its portfolio.

Principal investment strategies

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• foreign bonds and other bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.9 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

•Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

•Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

•Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

•Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

•Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

•Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

•Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

•Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

•Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

•Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

•Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

•Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

•Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

•Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 15.75% (2Q2002)

Lowest Quarter: -12.23% (4Q2008)

Year-to-Date (as of 3/31/11): 1.86%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL BOND FUND Class III, GMO International Bond Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		14.03%	5.16%	6.99%	7.07%	Dec. 22, 1993
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		12.10%	1.22%	3.43%	3.78%	Dec. 22, 1993
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		9.09%	2.04%	3.86%	4.07%	Dec. 22, 1993
J.P. Morgan Non-U.S. Government Bond Index	Class III	J.P. Morgan Non-U.S. Government Bond Index	(reflects no deduction for fees, expenses, or taxes)	6.78%	8.01%	7.64%	6.41%	Dec. 22, 1993

GMO STRATEGIC FIXED INCOME FUND

GMO STRATEGIC FIXED INCOME FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO STRATEGIC FIXED INCOME FUND		Class III, GMO Strategic Fixed Income Fund	Class VI, GMO Strategic Fixed Income Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.25%	0.25%
Shareholder service fee	[1]	0.15%	0.055%
Other expenses		0.03%	0.03%
Acquired fund fees and expenses (underlying fund expenses)	[2]	0.03%	0.03%
Total annual operating expenses		0.46%	0.37%
Expense reimbursement/waiver	[1]	(0.04%)	(0.04%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.42%	0.33%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO STRATEGIC FIXED INCOME FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Strategic Fixed Income Fund	Class III	43	[1]	150	267	609
Class VI, GMO Strategic Fixed Income Fund	Class VI	34	[1]	119	213	487

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 19% of the average value of its portfolio.

Principal investment strategies

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in fixed income securities (see “Name Policies”). The term “fixed income security” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in fixed income securities of any kind (e.g., fixed income securities of any maturity, duration or credit quality). The Fund may invest in any sector of the fixed income market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The Fund may invest all of its assets in below investment grade securities (also known as “junk bonds”). The sectors and types of fixed income securities in which the Fund may invest or hold include, but are not limited to:

• investment grade bonds denominated in various currencies, including bonds issued by the U.S. and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds;

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including below investment grade bonds); and

• asset-backed securities.

The Fund has substantial holdings of Short-Duration Collateral Fund (“SDCF”) (a Fund that primarily holds U.S. asset-backed securities) and World Opportunity Overlay Fund (“Overlay Fund”) (a Fund that invests in asset-backed securities and uses derivatives to attempt to exploit misvaluations in world interest rates, currencies and credit markets).

The Fund may also invest in exchange traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including SDCF and Overlay Fund, and also Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets), High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). For cash management purposes, the Fund may invest in unaffiliated money market funds.

The Fund, primarily though its investments in SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund’s interest rate duration will change depending on the Fund’s investments and the Manager’s assessment of different sectors of the bond market.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 8.76% (2Q2009)

Lowest Quarter: -17.50% (4Q2008)

Year-to-Date (as of 3/31/11): 2.05%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO STRATEGIC FIXED INCOME FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Strategic Fixed Income Fund	Class III	Return Before Taxes		5.18%			1.45%	Jul. 13, 2006
Return Before Taxes Class VI, GMO Strategic Fixed Income Fund	Class VI	Return Before Taxes		5.22%			1.54%	May 31, 2006
Return After Taxes on Distributions Class III, GMO Strategic Fixed Income Fund	Class III	Return After Taxes on Distributions		3.96%			(0.10%)	Jul. 13, 2006
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Strategic Fixed Income Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		3.35%			0.31%	Jul. 13, 2006
J.P. Morgan U.S. 3 Month Cash Index Class III, GMO Strategic Fixed Income Fund	Class III	J.P. Morgan U.S. 3 Month Cash Index	(reflects no deduction for fees, expenses, or taxes)	0.45%			3.19%	Jul. 13, 2006
J.P. Morgan U.S. 3 Month Cash Index Class VI, GMO Strategic Fixed Income Fund	Class VI	J.P. Morgan U.S. 3 Month Cash Index	(reflects no deduction for fees, expenses, or taxes)	0.45%			3.24%	May 31, 2006

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan).

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO CURRENCY HEDGED INTERNATIONAL BOND FUND Class III, GMO Currency Hedged International Bond Fund
Operating Expenses Column [Text]		Class III
Management fee		0.25%
Shareholder service fee	[1]	0.15%
Other expenses	[2]	0.25%
Acquired fund fees and expenses (underlying fund expenses)	[3]	0.05%
Total annual operating expenses		0.70%
Expense reimbursement/waiver	[1]	(0.26%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.44%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO CURRENCY HEDGED INTERNATIONAL BOND FUND Class III, GMO Currency Hedged International Bond Fund	Class III	45	[1]	202	373	868

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 51% of the average value of its portfolio.

Principal investment strategies

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund generally attempts to hedge at least 75% of its net foreign currency exposure into U.S. dollars.

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.6 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 8.23% (3Q2009)

Lowest Quarter: -11.09% (4Q2008)

Year-to-Date (as of 3/31/11): -0.37%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO CURRENCY HEDGED INTERNATIONAL BOND FUND Class III, GMO Currency Hedged International Bond Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		11.70%	2.44%	4.62%	8.02%	Sep. 30, 1994
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		9.94%	0.93%	2.37%	4.62%	Sep. 30, 1994
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		7.61%	1.19%	2.57%	4.79%	Sep. 30, 1994
J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) (Fund benchmark)	Class III	J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	3.71%	4.18%	5.03%	7.05%	Sep. 30, 1994
J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) + (Composite index)	Class III	J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) + (Composite index)		3.71%	4.18%	4.91%	7.11%	Sep. 30, 1994

GMO GLOBAL BOND FUND

GMO GLOBAL BOND FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan Global Government Bond Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO GLOBAL BOND FUND Class III, GMO Global Bond Fund
Operating Expenses Column [Text]		Class III
Management fee		0.19%
Shareholder service fee	[1]	0.15%
Other expenses	[2]	0.12%
Acquired fund fees and expenses (underlying fund expenses)	[3]	0.04%
Total annual operating expenses		0.50%
Expense reimbursement/waiver	[1]	(0.07%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.43%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO GLOBAL BOND FUND Class III, GMO Global Bond Fund	Class III	44	[1]	160	286	655

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 45% of the average value of its portfolio.

Principal investment strategies

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• foreign bonds and other bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.4 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 13.28% (2Q2002)

Lowest Quarter: -12.70% (4Q2008)

Year-to-Date (as of 3/31/11): 1.67%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO GLOBAL BOND FUND Class III, GMO Global Bond Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		14.14%	5.27%	6.54%	6.19%	Dec. 28, 1995
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		11.10%	2.81%	3.37%	3.40%	Dec. 28, 1995
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		9.12%	3.04%	3.65%	3.58%	Dec. 28, 1995
J.P. Morgan Global Government Bond Index	Class III	J.P. Morgan Global Government Bond Index	(reflects no deduction for fees, expenses, or taxes)	6.42%	7.35%	7.12%	5.88%	Dec. 28, 1995

GMO EMERGING COUNTRY DEBT FUND

GMO EMERGING COUNTRY DEBT FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan EMBI Global.

Fees and expenses

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO EMERGING COUNTRY DEBT FUND	Class III, GMO Emerging Country Debt Fund	Class IV, GMO Emerging Country Debt Fund
Shareholder Fees Column [Text]	Class III	Class IV
Purchase premium (as a percentage of amount invested)	0.50%	0.50%
Redemption fee (as a percentage of amount redeemed)	0.50%	0.50%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO EMERGING COUNTRY DEBT FUND		Class III, GMO Emerging Country Debt Fund	Class IV, GMO Emerging Country Debt Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.35%	0.35%
Shareholder service fee	[1]	0.15%	0.10%
Other expenses	[2]	0.15%	0.15%
Total annual operating expenses		0.65%	0.60%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO EMERGING COUNTRY DEBT FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Emerging Country Debt Fund USD ($)		Class III	168	[1]	314	472	933		Class III	116	[1]	257	410	856
Class IV, GMO Emerging Country Debt Fund USD ($)		Class IV	163	[1]	298	445	873		Class IV	111	[1]	241	383	796

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 21% of the average value of its portfolio.

Principal investment strategies

The Fund invests primarily in sovereign debt of emerging countries denominated in currencies of developed markets (e.g., U.S. dollar, Euro, Japanese yen, Swiss franc and British pound sterling). Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in debt investments tied economically to emerging countries (see “Name Policies”). The term “emerging countries” means the world’s less developed countries. The Fund typically gains its investment exposure by purchasing debt of sovereign issuers of emerging countries or by using derivatives, typically credit default swaps. The Fund also invests in U.S. and foreign asset-backed securities (including through Short-Duration Collateral Fund (“SDCF”) and World Opportunity Overlay Fund (“Overlay Fund”)). The Fund invests a substantial portion of its assets in below investment grade securities (also known as “junk bonds”). Generally, at least 75% of the Fund’s assets are denominated in, or hedged into, U.S. dollars.

In pursuing its investment objective, the Fund also typically uses exchange-traded and over-the-counter (“OTC”) derivatives, including options, swap contracts (in addition to credit default swaps), currency forwards (including currency forwards on currencies of developed markets), reverse repurchase agreements and futures. The Fund’s performance is likely to be more volatile than that of its benchmark.

The Manager emphasizes a “bottom-up” approach to examining and selecting investments and uses analytical techniques to identify inefficiencies in the pricing of emerging country debt investments and to identify investments the Manager believes are undervalued. The Manager also determines country allocations based on its outlook for a country.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets. The Manager normally seeks to cause the Fund’s estimated interest rate duration to approximate that of its benchmark (approximately 7.1 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities. Because the Fund typically invests in securities that are of lesser quality than those in its benchmark, in rapidly declining markets, the percentage decline in the value of the Fund is likely to exceed that of its benchmark.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. Sovereign debt of emerging countries is not widely traded and may be subject to purchase and sale restrictions. In addition, because the Fund typically invests in securities that are less liquid than those in its benchmark, in rapidly declining markets the percentage decline in the Fund’s investments is likely to exceed that of its benchmark.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in a limited number of countries, regions, sectors or companies creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 20.29% (3Q2009)

Lowest Quarter: -23.39% (4Q2008)

Year-to-Date (as of 3/31/11): 2.53%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO EMERGING COUNTRY DEBT FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Emerging Country Debt Fund	Class III	Return Before Taxes		24.39%	9.34%	14.88%	17.00%	Apr. 19, 1994
Return Before Taxes Class IV, GMO Emerging Country Debt Fund	Class IV	Return Before Taxes		24.50%	9.40%	14.95%	12.79%	Jan. 09, 1998
Return After Taxes on Distributions Class III, GMO Emerging Country Debt Fund	Class III	Return After Taxes on Distributions		19.02%	5.30%	10.08%	10.87%	Apr. 19, 1994
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Emerging Country Debt Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		15.35%	5.64%	10.06%	10.94%	Apr. 19, 1994
J.P. Morgan EMBI Global (Fund benchmark) Class III, GMO Emerging Country Debt Fund	Class III	J.P. Morgan EMBI Global (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	12.04%	8.36%	10.29%	12.08%	Apr. 19, 1994
J.P. Morgan EMBI Global (Fund benchmark) Class IV, GMO Emerging Country Debt Fund	Class IV	J.P. Morgan EMBI Global (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	12.04%	8.36%	10.29%	9.94%	Jan. 09, 1998
J.P. Morgan EMBI Global+ (Composite index) Class III, GMO Emerging Country Debt Fund	Class III	J.P. Morgan EMBI Global+ (Composite index)		12.04%	8.36%	10.29%	11.98%	Apr. 19, 1994
J.P. Morgan EMBI Global+ (Composite index) Class IV, GMO Emerging Country Debt Fund	Class IV	J.P. Morgan EMBI Global+ (Composite index)		12.04%	8.36%	10.29%	9.83%	Jan. 09, 1998

GMO SHORT-DURATION INVESTMENT FUND

GMO SHORT-DURATION INVESTMENT FUND

Investment objective

Provide current income.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO SHORT-DURATION INVESTMENT FUND Class III, GMO Short-Duration Investment Fund
Operating Expenses Column [Text]		Class III
Management fee		0.05%
Shareholder service fee		0.15%
Other expenses		0.94%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.02%
Total annual operating expenses		1.16%
Expense reimbursement	[2]	(0.94%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.22%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO SHORT-DURATION INVESTMENT FUND Class III, GMO Short-Duration Investment Fund	Class III	23	[1]	290	578	1,399

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 20% of the average value of its portfolio.

Principal investment strategies

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

Historically, the Fund has sought to provide current income to the extent consistent with the preservation of capital and liquidity. The Fund primarily holds shares of Short Duration Collateral Fund (“SDCF”). SDCF primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, SDCF has invested in government securities, corporate debt securities, money market instruments and commercial paper and has entered into credit default swaps, reverse repurchase agreements, and repurchase agreements. SDCF has also used other exchange-traded and over-the-counter (“OTC”) derivatives. The Fund also has invested directly in asset-backed securities issued by private issuers, U.S. government and agency securities (including securities neither guaranteed nor insured by the U.S. government), corporate debt securities, money market instruments, prime commercial paper and master demand notes, and certificates of deposit, bankers’ acceptances and other bank obligations.

Because of the deterioration in credit markets that became acute in 2008, the Fund, in particular through its investment in SDCF, currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

The Fund is not a money market fund and is not subject to the duration, quality, diversification and other requirements applicable to money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 6.11% (2Q2009)

Lowest Quarter: -10.36% (4Q2008)

Year-to-Date (as of 3/31/11): 0.72%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO SHORT-DURATION INVESTMENT FUND Class III, GMO Short-Duration Investment Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.		Inception Date
Return Before Taxes	Class III	Return Before Taxes		4.90%	2.42%	2.00%	4.10%	[1]	Apr. 18, 1990
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		4.68%	1.20%	0.76%	2.30%	[1]	Apr. 18, 1990
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		3.18%	1.35%	0.98%	2.42%	[1]	Apr. 18, 1990
J.P. Morgan U.S. 3 Month Cash Index	Class III	J.P. Morgan U.S. 3 Month Cash Index	(reflects no deduction for fees, expenses, or taxes)	0.45%	3.37%	2.99%	4.43%	[1]	Apr. 18, 1990

GMO SHORT-DURATION COLLATERAL FUND

GMO SHORT-DURATION COLLATERAL FUND

Investment objective

Total return comparable to that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO SHORT-DURATION COLLATERAL FUND
Management fee		none
Other expenses	[1]	0.03%
Total annual operating expenses		0.03%
Expense reimbursement	[2]	(0.02%)
Total annual operating expenses after expense reimbursement		0.01%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO SHORT-DURATION COLLATERAL FUND	GMO Short-Duration Collateral Fund	1	[1]	8	15	37

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 0% of the average value of its portfolio.

Principal investment strategies

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

The Fund primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, the Fund has invested in government securities, corporate debt securities, money market instruments and commercial paper and has entered into credit default swaps, reverse repurchase agreements and repurchase agreements. The Fund has also used other exchange-traded and over-the-counter (“OTC”) derivatives.

Because of the deterioration in credit markets that became acute in 2008, the Fund currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

Since October 2008, the Fund has declared and paid distributions when it has acquired a meaningful cash position rather than reinvesting that cash in portfolio securities. The Fund currently intends to continue this practice. A substantial portion of any such distributions could constitute a return of capital to shareholders for tax purposes. See “Distributions and Taxes” below for more information on the tax implications of such distributions.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns Years Ending December 31

Highest Quarter: 9.78% (2Q2009)

Lowest Quarter: -15.22% (4Q2008)

Year-to-Date (as of 3/31/11): 1.56%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO SHORT-DURATION COLLATERAL FUND	Label		Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Return Before Taxes			10.14%	3.65%		3.21%	Nov. 26, 2002
Return After Taxes on Distributions	Return After Taxes on Distributions	[1]		9.61%	2.31%		2.12%	Nov. 26, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Return After Taxes on Distributions and Sale of Fund Shares	[1]		6.57%	2.31%		2.06%	Nov. 26, 2002
J.P. Morgan U.S. 3 Month Cash Index	J.P. Morgan U.S. 3 Month Cash Index		(reflects no deduction for fees, expenses, or taxes)	0.45%	3.37%		2.86%	Nov. 26, 2002

GMO SHORT-DURATION COLLATERAL SHARE FUND

GMO SHORT-DURATION COLLATERAL SHARE FUND

Investment objective

Total return comparable to that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO SHORT-DURATION COLLATERAL SHARE FUND		Class III, GMO Short-Duration Collateral Share Fund	Class VI, GMO Short-Duration Collateral Share Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.05%	0.05%
Shareholder service fee		0.15%	0.055%
Other expenses		0.16%	0.16%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.01%	0.01%
Total annual operating expenses		0.37%	0.28%
Expense reimbursement	[2]	(0.16%)	(0.16%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.21%	0.12%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO SHORT-DURATION COLLATERAL SHARE FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Short-Duration Collateral Share Fund	Class III	22	[1]	107	201	475
Class VI, GMO Short-Duration Collateral Share Fund	Class VI	12	[1]	78	150	363

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 5% of the average value of its portfolio.

Principal investment strategies

The Fund invests substantially all of its assets in Short-Duration Collateral Fund (“SDCF”) (see page 100 for a discussion of SDCF). The Fund also may invest in U.S. Treasury Fund, unaffiliated money market funds, cash and cash equivalents. Its investment objective and principal investment strategies, therefore, are substantially similar to those of SDCF. SDCF is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

SDCF primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, SDCF has invested in government securities, corporate debt securities, money market instruments, and commercial paper, and has entered into credit default swaps, reverse repurchase agreements and repurchase agreements. SDCF has also used exchange-traded and over-the-counter (“OTC”) derivatives. Because of the deterioration in credit markets that became acute in 2008, the Fund, through its holdings of SDCF, currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for SDCF.

Since October of 2008, SDCF has declared and paid distributions when it has acquired a meaningful cash position rather than reinvesting that cash in portfolio securities. SDCF currently intends to continue this practice. A substantial portion of any such distributions could constitute a return of capital to SDCF shareholders, including the Fund, for tax purposes. Therefore, if the Fund, in turn, distributes these amounts to its shareholders, the Fund’s distributions similarly could constitute a return of capital to Fund shareholders for tax purposes. See “Distributions and Taxes” below for more information on the tax implications of such distributions.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. Because the Fund invests substantially all of its assets in SDCF, the most significant risks of investing in the Fund are the risks to which the Fund is exposed through SDCF, which include those outlined in the following brief summary of principal risks. For a more complete discussion of these risks, see “Description of Principal Risks.” The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified.

• Market Risk – Fixed Income Securities – Typically, the market value of SDCF’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent SDCF from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 9.62% (2Q2009)

Lowest Quarter: -14.97% (4Q2008)

Year-to-Date (as of 3/31/11): 1.52%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO SHORT-DURATION COLLATERAL SHARE FUND	Column		Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Short-Duration Collateral Share Fund	Class III		Return Before Taxes		9.92%			3.00%	Dec. 28, 2006
Return Before Taxes Class VI, GMO Short-Duration Collateral Share Fund	Class VI	[1]	Return Before Taxes		9.92%			3.43%	Mar. 01, 2006
Return After Taxes on Distributions Class III, GMO Short-Duration Collateral Share Fund	Class III		Return After Taxes on Distributions		9.54%			1.78%	Dec. 28, 2006
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Short-Duration Collateral Share Fund	Class III		Return After Taxes on Distributions and Sale of Fund Shares		6.45%			1.81%	Dec. 28, 2006
J.P. Morgan U.S. 3 Month Cash Index Class III, GMO Short-Duration Collateral Share Fund	Class III		J.P. Morgan U.S. 3 Month Cash Index	(reflects no deduction for fees, expenses, or taxes)	0.45%			2.90%	Dec. 28, 2006
J.P. Morgan U.S. 3 Month Cash Index Class VI, GMO Short-Duration Collateral Share Fund	Class VI	[1]	J.P. Morgan U.S. 3 Month Cash Index	(reflects no deduction for fees, expenses, or taxes)	0.45%			3.33%	Mar. 01, 2006

GMO INFLATION INDEXED PLUS BOND FUND

GMO INFLATION INDEXED PLUS BOND FUND

Investment objective

Total return in excess of that of its benchmark, the Barclays Capital U.S. Treasury Inflation Notes Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO INFLATION INDEXED PLUS BOND FUND		Class III, GMO Inflation Indexed Plus Bond Fund	Class VI, GMO Inflation Indexed Plus Bond Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.25%	0.25%
Shareholder service fee	[1]	0.15%	0.055%
Other expenses	[2]	0.19%	0.19%
Acquired fund fees and expenses (underlying fund expenses)	[3]	0.08%	0.08%
Total annual operating expenses		0.67%	0.58%
Expense reimbursement/waiver	[1]	(0.20%)	(0.20%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.47%	0.38%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INFLATION INDEXED PLUS BOND FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Inflation Indexed Plus Bond Fund	Class III	48	[1]	199	362	838
Class VI, GMO Inflation Indexed Plus Bond Fund	Class VI	39	[1]	168	308	718

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 81% of the average value of its portfolio.

Principal investment strategies

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to inflation indexed bonds and/or the global interest rate, credit and currency markets);

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• non-inflation indexed (or nominal) fixed income securities issued by the U.S. and foreign governments and their agencies or instrumentalities (including securities neither guaranteed nor insured by the U.S. government) and by corporations (to gain direct exposure to such securities and/or for use as part of a synthetic position);

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposures to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in inflation indexed bonds (see “Name Policies”). For purposes of this Prospectus, the term “inflation indexed bonds” includes instruments that are “linked” to general measures of inflation because their principal and/or interest components change with general movements of inflation in the country of issue.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads. In addition, increases in real interest rates may not be accompanied by increases in nominal interest rates. In such instances, the value of inflation indexed bonds may experience greater declines than non-inflation indexed (or nominal) fixed income investments with similar maturities. There can be no assurance that the value of the Fund’s inflation indexed bond investments will change in the same proportion as changes in nominal interest rates, and short-term increases in inflation may lead to a decline in their value.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 9.31% (3Q2009)

Lowest Quarter: -21.90% (4Q2008)

Year-to-Date (as of 3/31/11): 2.92%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INFLATION INDEXED PLUS BOND FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Inflation Indexed Plus Bond Fund	Class III	Return Before Taxes		13.93%			3.96%	Jun. 29, 2006
Return Before Taxes Class VI, GMO Inflation Indexed Plus Bond Fund	Class VI	Return Before Taxes		14.15%			3.98%	May 31, 2006
Return After Taxes on Distributions Class III, GMO Inflation Indexed Plus Bond Fund	Class III	Return After Taxes on Distributions		11.45%			0.70%	Jun. 29, 2006
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Inflation Indexed Plus Bond Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		9.20%			1.41%	Jun. 29, 2006
Barclays Capital U.S. Treasury Inflation Notes Index Class III, GMO Inflation Indexed Plus Bond Fund	Class III	Barclays Capital U.S. Treasury Inflation Notes Index	(reflects no deduction for fees, expenses, or taxes)	6.31%			6.46%	Jun. 29, 2006
Barclays Capital U.S. Treasury Inflation Notes Index Class VI, GMO Inflation Indexed Plus Bond Fund	Class VI	Barclays Capital U.S. Treasury Inflation Notes Index	(reflects no deduction for fees, expenses, or taxes)	6.31%			6.31%	May 31, 2006

GMO U.S. TREASURY FUND

GMO U.S. TREASURY FUND

Investment objective

Liquidity and safety of principal with

current income as a secondary objective.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. TREASURY FUND
Management fee	[1]	0.08%
Other expenses		0.03%
Total annual operating expenses		0.11%
Expense reimbursement	[1]	(0.03%)
Total annual operating expenses after expense reimbursement		0.08%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO U.S. TREASURY FUND	GMO U.S. Treasury Fund	8	[1]	32	59	138

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 0% of the average value of its portfolio.

Principal investment strategies

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in Direct U.S. Treasury Obligations and repurchase agreements collateralized by these Obligations (see “Name Policies”). “Direct U.S. Treasury Obligations” include U.S. Treasury bills, bonds and notes and other securities issued by the U.S. Treasury, as well as Separately Traded Registered Interest and Principal Securities (STRIPS) and other zero-coupon securities. The Manager normally seeks to maintain an interest rate duration of one year or less for the Fund’s portfolio. For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses — Fixed Income Funds — Duration.”

The Fund may also enter into repurchase agreements, under which the Fund purchases a security backed by the full faith and credit of the U.S. government from a seller who simultaneously commits to repurchase, on an agreed upon date in the future, the security from the Fund at the original purchase price plus an agreed upon amount representing the original purchase price plus interest. The counterparties in repurchase agreements are typically broker-dealers and banks, and the safety of the arrangement is dependent on, among other things, the Fund having an interest in the security that can be realized in the event of the insolvency of the counterparty.

In addition to Direct U.S. Treasury Obligations, the Fund may invest in other fixed-income securities that are backed by the full faith and credit of the U.S. government, such as guaranteed securities issued by the Government National Mortgage Association (GNMA) and the Federal Deposit Insurance Corporation (FDIC). For cash management purposes, the Fund may invest in unaffiliated money market funds.

Although the fixed-income securities purchased by the Fund normally will have a stated or remaining maturity of one year or less, Direct U.S. Treasury Obligations purchased pursuant to repurchase agreements may not, and, therefore, if the counterparty to the repurchase agreement defaults, the Fund may end up owning a security with a stated or remaining maturity of more than one year.

The Fund is not a money market fund and is not subject to the duration, quality, diversification and other requirements applicable to money market funds.

In selecting U.S. Treasury securities for the Fund’s portfolio, the Manager focuses primarily on the relative attractiveness of different obligations (such as bonds, notes or bills), which can vary depending on the general level of interest rates as well as supply/demand imbalances and other market conditions.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s U.S. Treasury and other fixed income securities will decline during periods of rising interest rates, and yields on the Fund’s securities may equal or approach zero under some market conditions.

• Credit Risk – Securities issued by the U.S. Treasury or U.S. government agencies generally present minimal credit risk. However, a security backed by the full faith and credit of the U.S. government is guaranteed only as to the timely payment of interest and principal when held to maturity. The market prices for such securities are not guaranteed and will fluctuate.

• Focused Investment Risk – Focusing investments in a particular type of security (e.g., Direct U.S. Treasury Obligations) creates additional risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns Year Ending December 31

Highest Quarter: 0.07% (2Q2010)

Lowest Quarter: -0.02% (1Q2010)

Year-to-Date (as of 3/31/11): 0.03%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO U.S. TREASURY FUND	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Return Before Taxes		0.10%			0.21%	Mar. 17, 2009
Return After Taxes on Distributions	Return After Taxes on Distributions		0.05%			0.14%	Mar. 17, 2009
Return After Taxes on Distributions and Sale of Fund Shares	Return After Taxes on Distributions and Sale of Fund Shares		0.06%			0.14%	Mar. 17, 2009
Citigroup 3-Month Treasury Bill Index	Citigroup 3-Month Treasury Bill Index	(reflects no deduction for fees, expenses, or taxes)	0.13%			0.14%	Mar. 17, 2009

GMO ASSET ALLOCATION BOND FUND

GMO ASSET ALLOCATION BOND FUND

Investment objective

Total return in excess of that of its benchmark, the Citigroup 3-Month Treasury Bill Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO ASSET ALLOCATION BOND FUND		Class III, GMO Asset Allocation Bond Fund	Class VI, GMO Asset Allocation Bond Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.25%	0.25%
Shareholder service fee	[1]	0.15%	0.055%
Other expenses	[2]	0.08%	0.08%
Total annual operating expenses		0.48%	0.39%
Expense reimbursement/waiver	[1]	(0.04%)	(0.04%)
Total annual operating expenses after expense reimbursement/waiver		0.44%	0.35%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO ASSET ALLOCATION BOND FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
Class III, GMO Asset Allocation Bond Fund	Class III	45	[1]	148	260	589
Class VI, GMO Asset Allocation Bond Fund	Class VI	36	[1]	119	210	477

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 315% of the average value of its portfolio.

Principal investment strategies

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in bonds of any kind (e.g., bonds of any maturity, duration or credit quality).

The Fund may invest in any sector of the bond market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The sectors and types of bonds in which the Fund may invest include, but are not limited to:

• investment grade bonds denominated in various currencies, including bonds issued by the U.S. and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds (also known as “junk bonds”);

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including junk bonds); and

• asset-backed securities, including mortgage related and mortgage-backed securities.

The Fund may also invest in exchange traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). The Fund also may invest in unaffiliated money market funds for cash management purposes.

The Fund may invest up to 100% of its assets in junk bonds.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund’s interest rate duration will change depending on the Fund’s investments and the Manager’s assessment of different sectors of the bond market.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund's fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. The Fund's investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund's use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Year Ending December 31

Highest Quarter: 1.83% (3Q2010)

Lowest Quarter: -0.36% (4Q2010)

Year-to-Date (as of 3/31/11): 1.94%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO ASSET ALLOCATION BOND FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Asset Allocation Bond Fund	Class III	Return Before Taxes		4.02%			5.85%	Mar. 27, 2009
Return Before Taxes Class VI, GMO Asset Allocation Bond Fund	Class VI	Return Before Taxes		4.14%			6.24%	Mar. 18, 2009
Return After Taxes on Distributions Class III, GMO Asset Allocation Bond Fund	Class III	Return After Taxes on Distributions		0.95%			3.49%	Mar. 27, 2009
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Asset Allocation Bond Fund	Class III	Return After Taxes on Distribution and Sale of Fund Shares		2.63%			3.66%	Mar. 27, 2009
Citigroup 3-Month Treasury Bill Index Class III, GMO Asset Allocation Bond Fund	Class III	Citigroup 3-Month Treasury Bill Index	(reflects no deduction for fees, expenses, or taxes)	0.13%			0.14%	Mar. 27, 2009
Citigroup 3-Month Treasury Bill Index Class VI, GMO Asset Allocation Bond Fund	Class VI	Citigroup 3-Month Treasury Bill Index	(reflects no deduction for fees, expenses, or taxes)	0.13%			0.14%	Mar. 18, 2009

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND

Investment objective

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index.

Fees and expenses

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO ASSET ALLOCATION INTERNATIONAL BOND FUND		Class III, GMO Asset Allocation International Bond Fund	Class VI, GMO Asset Allocation International Bond Fund
Operating Expenses Column [Text]		Class III	Class VI
Management fee		0.25%	0.25%
Shareholder service fee	[1]	0.15%	0.055%
Other expenses	[2]	0.18%	0.18%
Total annual operating expenses	[2]	0.58%	0.49%
Expense reimbursement/waiver	[1][2]	(0.18%)	(0.18%)
Total annual operating expenses after expense reimbursement/waiver	[2]	0.40%	0.31%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO ASSET ALLOCATION INTERNATIONAL BOND FUND (USD $)	Expense Example, By Year, Column [Text]	1 Year	3 Years
Class III, GMO Asset Allocation International Bond Fund	Class III	59	186
Class VI, GMO Asset Allocation International Bond Fund	Class VI	50	157

Portfolio turnover

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.

Principal investment strategies

The Manager pursues the Fund's investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund's strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in bonds of any kind (e.g., bonds of any maturity, duration or credit quality). While the Fund principally invests in non-U.S. bonds, it may invest in any sector of the bond market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The sectors and types of bonds in which the Fund may invest include, but are not limited to:

• foreign government securities and other investment grade bonds denominated in various currencies, including bonds issued by the U.S. government, and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds (also known as “junk bonds”);

• inflation indexed bonds issued by foreign governments and the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including junk bonds); and

• asset-backed securities, including mortgage related and mortgage-backed securities.

The Fund may also invest in exchange-traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). The Fund also may invest in unaffiliated money market funds for cash management purposes.

The Fund may invest up to 100% of its assets in junk bonds.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund's interest rate duration will change depending on the Fund's investments and the Manager's assessment of different sectors of the bond market.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Currency Risk – Fluctuations in exchange rates will adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund's fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. The Fund's investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Leveraging Risk – The Fund's use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions or sectors or in industries with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO U.S. EQUITY ALLOCATION FUND

GMO U.S. EQUITY ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the Russell 3000 Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO U.S. EQUITY ALLOCATION FUND Class III, GMO U.S. Equity Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	none
Redemption fee (as a percentage of amount redeemed)	none

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. EQUITY ALLOCATION FUND Class III, GMO U.S. Equity Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.06%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.39%
Total annual operating expenses		0.45%
Expense reimbursement	[2]	(0.06%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.39%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO U.S. EQUITY ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO U.S. Equity Allocation Fund USD ($)		Class III	40	[1]	151	273	629		Class III	40	[1]	151	273	629

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 7% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of the U.S. Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of Flexible Equities Fund (together with the U.S. Equity Funds, the “underlying Funds”). In addition, the Fund may hold securities directly. The Fund primarily seeks exposure to U.S. equity investments (which may include both growth and value style equities and equities of any market capitalization). The Fund also may have exposure to foreign equity investments. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among major sectors in the U.S. equity market (large-cap value, large-cap growth, large-cap core, small- and mid-cap value, small- and mid-cap growth and real estate/REIT) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund's or the underlying Fund's performance more than if the Fund or the underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Leveraging Risk – The use of derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

^[10]

Highest Quarter: 18.06% (2Q2003)

Lowest Quarter: -16.54% (3Q2002)

Year to Date (as of 3/31/11): 4.15%

Average Annual Total Returns Periods Ending December 31, 2010

^[10]

Average Annual Total Returns GMO U.S. EQUITY ALLOCATION FUND Class III, GMO U.S. Equity Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		7.70%	1.24%	4.15%	9.97%	Dec. 31, 1992
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		7.38%	0.17%	3.24%	6.15%	Dec. 31, 1992
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		5.38%	1.90%	3.59%	7.07%	Dec. 31, 1992
Russell 3000 Index (Fund benchmark)	Class III	Russell 3000 Index (Fund benchmark)	(reflects no deduction for fees, expenses, or taxes)	16.93%	2.74%	2.16%	8.29%	Dec. 31, 1992
Russell 3000 ++ Index (Composite index)	Class III	Russell 3000 ++ Index (Composite index)		16.93%	2.74%	2.03%	8.51%	Dec. 31, 1992

GMO INTERNATIONAL EQUITY ALLOCATION FUND

GMO INTERNATIONAL EQUITY ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the MSCI ACWI ex-U.S. Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO INTERNATIONAL EQUITY ALLOCATION FUND Class III, GMO International Equity Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.21%
Redemption fee (as a percentage of amount redeemed)	0.21%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO INTERNATIONAL EQUITY ALLOCATION FUND Class III, GMO International Equity Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.01%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.72%
Total annual operating expenses		0.73%
Expense reimbursement	[2]	(0.01%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.72%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL EQUITY ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO International Equity Allocation Fund USD ($)		Class III	116	[1]	287	473	1,011		Class III	94	[1]	264	447	979

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 13% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), as well as to the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 21.94% (2Q2009)

Lowest Quarter: -20.16% (3Q2008)

Year-to-Date (as of 3/31/11): 3.35%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL EQUITY ALLOCATION FUND Class III, GMO International Equity Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		12.55%	4.55%	9.89%	8.61%	Oct. 11, 1996
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		12.29%	2.28%	8.11%	6.73%	Oct. 11, 1996
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		8.32%	3.51%	8.23%	6.83%	Oct. 11, 1996
MSCI ACWI ex-U.S. Index	Class III	MSCI ACWI ex-U.S. Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.15%	4.82%	5.55%	5.93%	Oct. 11, 1996

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the MSCI EAFE Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO International Opportunities Equity Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	none
Redemption fee (as a percentage of amount redeemed)	none

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO International Opportunities Equity Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.02%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.63%
Total annual operating expenses		0.65%
Expense reimbursement	[2]	(0.02%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.63%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO International Opportunities Equity Allocation Fund USD ($)		Class III	64	[1]	217	383	864		Class III	64	[1]	217	383	864

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 14% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), as well as to the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 19.55% (2Q2009)

Lowest Quarter: -18.80% (3Q2008)

Year-to-Date (as of 3/31/11): 2.96%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO International Opportunities Equity Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		10.86%			1.29%	Jun. 05, 2006
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		10.65%			(0.24%)	Jun. 05, 2006
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		7.33%			0.79%	Jun. 05, 2006
MSCI EAFE Index	Class III	MSCI EAFE Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%			0.31%	Jun. 05, 2006

GMO GLOBAL EQUITY ALLOCATION FUND

GMO GLOBAL EQUITY ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the MSCI ACWI Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO GLOBAL EQUITY ALLOCATION FUND Class III, GMO Global Equity Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.13%
Redemption fee (as a percentage of amount redeemed)	0.13%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO GLOBAL EQUITY ALLOCATION FUND Class III, GMO Global Equity Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.02%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.58%
Total annual operating expenses		0.60%
Expense reimbursement	[2]	(0.02%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.58%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO GLOBAL EQUITY ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Global Equity Allocation Fund USD ($)		Class III	86	[1]	226	379	825		Class III	72	[1]	212	363	805

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 6% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds and the U.S. Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., U.S. equity, foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 18.79% (2Q2003)

Lowest Quarter: -15.65% (4Q2008)

Year-to-Date (as of 3/31/11): 3.49%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO GLOBAL EQUITY ALLOCATION FUND Class III, GMO Global Equity Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		9.69%	3.14%	6.87%	8.30%	Nov. 26, 1996
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		9.45%	1.49%	5.38%	6.00%	Nov. 26, 1996
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.52%	2.40%	5.59%	6.22%	Nov. 26, 1996
MSCI ACWI Index (Fund benchmark)	Class III	MSCI ACWI Index (Fund benchmark)	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	12.67%	3.44%	3.20%	5.26%	Nov. 26, 1996
MSCI ACWI + Index (Composite index)	Class III	MSCI ACWI + Index (Composite index)		12.67%	2.24%	2.12%	5.37%	Nov. 26, 1996

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the MSCI World Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO World Opportunities Equity Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	none
Redemption fee (as a percentage of amount redeemed)	none

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO World Opportunities Equity Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.02%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.53%
Total annual operating expenses		0.55%
Expense reimbursement	[2]	(0.01%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.54%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO World Opportunities Equity Allocation Fund USD ($)		Class III	55	[1]	184	324	733		Class III	55	[1]	184	324	733

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 20% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds and the U.S. Equity Funds (see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund’s primary exposure is to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., U.S. equity, foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund’s holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund’s loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 14.41% (3Q2010)

Lowest Quarter: -15.27% (4Q2008)

Year-to-Date (as of 3/31/11): 3.34%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND Class III, GMO World Opportunities Equity Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		9.00%	3.25%		4.76%	Jun. 16, 2005
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		8.75%	2.12%		3.61%	Jun. 16, 2005
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		6.18%	2.59%		3.87%	Jun. 16, 2005
MSCI World Index	Class III	MSCI World Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%	2.43%		3.88%	Jun. 16, 2005

GMO GLOBAL BALANCED ASSET ALLOCATION FUND

GMO GLOBAL BALANCED ASSET ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the GMO Global Balanced Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO GLOBAL BALANCED ASSET ALLOCATION FUND Class III, GMO Global Balance Asset Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.10%
Redemption fee (as a percentage of amount redeemed)	0.10%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO GLOBAL BALANCED ASSET ALLOCATION FUND Class III, GMO Global Balance Asset Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.01%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.53%
Total annual operating expenses		0.54%
Expense reimbursement	[2]	(0.01%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.53%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO GLOBAL BALANCED ASSET ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Global Balance Asset Allocation Fund USD ($)		Class III	75	[1]	217	372	824		Class III	64	[1]	206	360	808

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund may be exposed to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), U.S. and foreign fixed income securities (including asset-backed securities and other fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, U.S. fixed income, foreign fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund’s holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments. The Manager, however, intends to invest at least 25% of the Fund’s assets in fixed income investments and at least 25% in equity investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund’s loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices, and composite indices, including the Fund’s benchmark, computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 14.27% (2Q2003)

Lowest Quarter: -9.87% (3Q2001)

Year-to-Date (as of 3/31/11): 2.60%

Average Annual Total Returns Periods Ending December 31, 2009

^[11]

Average Annual Total Returns GMO GLOBAL BALANCED ASSET ALLOCATION FUND Class III, GMO Global Balance Asset Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		7.17%	5.18%	7.63%	7.95%	Jun. 28, 1996
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		6.70%	3.22%	5.86%	5.74%	Jun. 28, 1996
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		4.81%	3.55%	5.77%	5.73%	Jun. 28, 1996
MSCI ACWI Index	Class III	MSCI ACWI Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	12.67%	3.44%	3.20%	5.62%	Jun. 28, 1996
Barclays Capital U.S. Aggregate Index	Class III	Barclays Capital U.S. Aggregate Index	(reflects no deduction for fees, expenses, or taxes)	6.54%	5.80%	5.84%	6.35%	Jun. 28, 1996
GMO Global Balanced Index (Fund benchmark)	Class III	GMO Global Balanced Index (Fund benchmark)		11.05%	4.31%	3.98%	6.61%	Jun. 28, 1996
Global Balanced Benchmark+ Index (Composite index)	Class III	Global Balanced Benchmark+ Index (Composite index)		11.05%	4.31%	2.49%	5.12%	Jun. 28, 1996

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND

Investment objective

Total return greater than that of its benchmark, the GMO Strategic Opportunities Allocation Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND Class III, GMO Strategic Opportunities Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	none
Redemption fee (as a percentage of amount redeemed)	none

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND Class III, GMO Strategic Opportunities Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.01%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.54%
Total annual operating expenses		0.55%
Expense reimbursement	[2]	(0.01%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.54%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Strategic Opportunities Allocation Fund USD ($)		Class III	55	[1]	190	338	767		Class III	55	[1]	190	338	767

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 36% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund may have exposure to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), U.S. and foreign fixed income securities (including asset-backed securities and other fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, U.S. fixed income, foreign fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices and the Fund’s benchmark (which is a composite index computed by the Manager). Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 11.73% (2Q2009)

Lowest Quarter: -10.19% (4Q2008)

Year-to-Date (as of 3/31/11): 2.98%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND Class III, GMO Strategic Opportunities Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		7.96%	5.53%		6.72%	May 31, 2005
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		7.57%	3.86%		5.09%	May 31, 2005
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		5.42%	4.03%		5.08%	May 31, 2005
MSCI World Index	Class III	MSCI World Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%	2.43%		4.14%	May 31, 2005
Barclays Capital U.S. Aggregate Index	Class III	Barclays Capital U.S. Aggregate Index	(reflects no deduction for fees, expenses, or taxes)	6.54%	5.80%		5.26%	May 31, 2005
GMO Strategic Opportunities Allocation Index (Fund benchmark)	Class III	GMO Strategic Opportunities Allocation Index (Fund benchmark)		10.90%	3.63%		4.76%	May 31, 2005

GMO BENCHMARK-FREE ALLOCATION FUND

GMO BENCHMARK-FREE ALLOCATION FUND

Investment objective

The Fund seeks a positive total return. The Fund does not have a particular securities market index as a benchmark and does not seek to outperform a particular index or blend of indices (i.e., the Fund seeks positive return, not “relative” return).

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees	GMO BENCHMARK-FREE ALLOCATION FUND Class III, GMO Benchmark-Free Allocation Fund
Shareholder Fees Column [Text]	Class III
Purchase premium (as a percentage of amount invested)	0.09%
Redemption fee (as a percentage of amount redeemed)	0.09%

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

^[12]

Annual Fund Operating Expenses		GMO BENCHMARK-FREE ALLOCATION FUND Class III, GMO Benchmark-Free Allocation Fund
Operating Expenses Column [Text]		Class III
Management fee		none
Shareholder service fee		none
Other expenses		0.02%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.57%
Total annual operating expenses		0.59%
Expense reimbursement	[2]	(0.01%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		0.58%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO BENCHMARK-FREE ALLOCATION FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do not sell your shares
Class III, GMO Benchmark-Free Allocation Fund USD ($)		Class III	78	[1]	252	442	991		Class III	68	[1]	242	431	977

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 19% of the average value of its portfolio.

Principal investment strategies

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund implements its strategy by allocating its assets among asset classes represented by the underlying Funds (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities). The Fund is not restricted in its exposure to any particular asset class, and at times may be substantially invested in underlying Funds that primarily invest in a single asset class (e.g., Fixed Income Funds). In addition, the Fund is not restricted in its exposure to any particular market. Although the Fund generally will have exposure to both emerging countries and developed countries, including the U.S., at times, it also may have substantial exposure to a particular country or type of country (e.g., emerging countries).

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments. The Manager's ability to shift investments among the underlying Funds is not subject to any limits. The Fund may invest substantially all of its assets in a few underlying Funds that primarily invest in the same asset class and may, at times, also invest a substantial portion of its assets in a single underlying Fund.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk — Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of companies with smaller market capitalizations often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalization.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Consumer Price Index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 9.19% (2Q2009)

Lowest Quarter: -6.90% (4Q2008)

Year-to-Date (as of 3/31/11): 1.92%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO BENCHMARK-FREE ALLOCATION FUND Class III, GMO Benchmark-Free Allocation Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class III	Return Before Taxes		4.72%	7.11%		12.00%	Jul. 23, 2003
Return After Taxes on Distributions	Class III	Return After Taxes on Distributions		4.19%	4.42%		9.27%	Jul. 23, 2003
Return After Taxes on Distributions and Sale of Fund Shares	Class III	Return After Taxes on Distributions and Sale of Fund Shares		3.14%	4.86%		9.18%	Jul. 23, 2003
MSCI World Index	Class III	MSCI World Index	(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)	11.76%	2.43%		7.14%	Jul. 23, 2003
Consumer Price Index	Class III	Consumer Price Index	(reflects no deduction for fees, expenses, or taxes)	1.25%	2.18%		2.47%	Jul. 23, 2003

GMO ALPHA ONLY FUND

GMO ALPHA ONLY FUND

Investment objective

Seeks to outperform the Fund’s benchmark, the Citigroup 3-Month Treasury Bill Index.

Fees and expenses

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees (fees paid directly from your investment)

Shareholder Fees GMO ALPHA ONLY FUND	Class III, GMO Alpha Only Fund	Class IV, GMO Alpha Only Fund
Shareholder Fees Column [Text]	Class III	Class IV
Purchase premium (as a percentage of amount invested)	none	none
Redemption fee (as a percentage of amount redeemed)	none	none

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses GMO ALPHA ONLY FUND		Class III, GMO Alpha Only Fund	Class IV, GMO Alpha Only Fund
Operating Expenses Column [Text]		Class III	Class IV
Management fee		0.50%	0.50%
Shareholder service fee	[1]	0.15%	0.10%
Other expenses		0.04%	0.04%
Acquired fund fees and expenses (underlying fund expenses)	[2]	0.44%	0.44%
Total annual operating expenses		1.13%	1.08%
Expense reimbursement/waiver	[1]	(0.46%)	(0.46%)
Total annual operating expenses after expense reimbursement/waiver (Fund and underlying fund expenses)		0.67%	0.62%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example GMO ALPHA ONLY FUND	Expense Example by, Year, Caption [Text]	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years	Expense Example, No Redemption, By Year, Caption [Text]	Expense Example, No Redemption, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO Trust	If you sell your shares							If you do no sell your shares
Class III, GMO Alpha Only Fund USD ($)		Class III	68	[1]	320	591	1,365		Class III	68	[1]	320	591	1,365
Class IV, GMO Alpha Only Fund USD ($)		Class IV	63	[1]	304	564	1,308		Class IV	63	[1]	304	564	1,308

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 89% of the average value of its portfolio.

Principal investment strategies

The Fund's investment program involves having both long and short investment exposures. The Fund seeks to construct a portfolio in which it has long investment exposure to asset classes and sub-asset classes that it expects will outperform relative to the asset classes and sub-asset classes to which it has short investment exposure.

To gain long investment exposure, the Fund invests primarily in shares of the U.S. Equity Funds and the International Equity Funds, and also may invest in shares of Emerging Country Debt Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may gain long investment exposure by investing in securities directly, rather than through the underlying Funds.

To gain short investment exposure, the Fund may use over-the-counter (“OTC”) and exchange-traded derivatives (including futures, swap contracts and currency forwards) and make short sales of securities (e.g., shares of exchange-traded funds), including short sales of securities the Fund does not own. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity and emerging country debt) and sub-asset classes (e.g., small- to mid-cap stocks in the foreign equity asset class and quality stocks in the U.S. equity and emerging country equity asset classes) to select the underlying Funds and securities in which the Fund invests or takes short positions and to decide how much to invest and/or short in each. The Manager changes the Fund's holdings in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund's or the underlying Fund's performance more than if the Fund or the underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund or an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund or an underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. In addition, the value of the Fund's shares will be adversely affected if the equity investments that are the subject of the Fund's short positions appreciate in value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent a Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests will not perform as expected or that the Fund will invest in underlying funds with higher fees or expenses.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives may cause the Fund's portfolio to be leveraged. The Fund and some underlying Funds are not limited in the extent to which they may use derivatives or in the absolute face value of their derivative positions. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Short Sales Risk – The Fund runs the risk that the Fund's loss on a short sale of securities that the Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds, or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class III Shares Years Ending December 31

Highest Quarter: 7.39% (1Q2001)

Lowest Quarter: -4.81% (2Q2009)

Year-to-Date (as of 3/31/11): -1.43%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO ALPHA ONLY FUND	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes Class III, GMO Alpha Only Fund	Class III	Return Before Taxes		(4.02%)	1.95%	4.59%	4.18%	Jul. 29, 1994
Return Before Taxes Class IV, GMO Alpha Only Fund	Class IV	Return Before Taxes		(3.98%)			1.80%	Mar. 02, 2006
Return After Taxes on Distributions Class III, GMO Alpha Only Fund	Class III	Return After Taxes on Distributions		(4.02%)	(2.36%)	1.86%	1.64%	Jul. 29, 1994
Return After Taxes on Distributions and Sale of Fund Shares Class III, GMO Alpha Only Fund	Class III	Return After Taxes on Distributions and Sale of Fund Shares		(2.62%)	2.55%	3.77%	3.05%	Jul. 29, 1994
Citigroup 3-Month Treasury Bill Index Class III, GMO Alpha Only Fund	Class III	Citigroup 3-Month Treasury Bill Index	(reflects no deduction for fees, expenses, or taxes)	0.13%	2.30%	2.26%	3.44%	Jul. 29, 1994
Citigroup 3-Month Treasury Bill Index Class IV, GMO Alpha Only Fund	Class IV	Citigroup 3-Month Treasury Bill Index	(reflects no deduction for fees, expenses, or taxes)	0.13%			2.23%	Mar. 02, 2006

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.33% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.33% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.33% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.33% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.38% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] An additional purchase premium and redemption fee of 0.005% is charged for any purchases/redemptions (or any portion of a purchase/redemption) effected in a currency other than the U.S. dollar.

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.45% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under 'Expense Reimbursement' in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Performance of Class III shares prior to June 28, 1996 is that of the private investment pool and reflects the pool's higher annual operating expenses. The pool was not registered as an investment company and therefore was not subject to restrictions imposed on the Fund by the Investment Company Act of 1940 and the Internal Revenue Code of 1986. Had the pool been subject to these restrictions, its performance may have been adversely affected.

[2] Information on the Fund's return after taxes is unavailable prior to June 28, 1996, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.70% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without consent by the Fund's Board of Trustees.

[1] After reimbursement

[1] Performance of Class III shares prior to June 30, 2000 is that of the private investment pool, restated to reflect the Fund's higher annual operating expenses. The pool was not registered as an investment company and therefore was not subject to certain restrictions imposed on the Fund by the Investment Company Act of 1940 and the Internal Revenue Code of 1986. Had the pool been subject to these restrictions, its performance may have been adversely affected.

[2] For the period from March 16, 2009 to August 12, 2009, no Class IV shares were outstanding. The returns shown in the table for that period are those of Class III shares, which have higher expenses.

[3] Information on the Fund's return after taxes is unavailable prior to June 30, 2000, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[1] Applies only to shares acquired on or after June 1, 1995 (including shares acquired by reinvestment of dividends or other distribution). With respect to Class III shares purchased through third-party intermediaries and any shares acquired prior to March 27, 2002, the level of redemption fee charged by the Fund is 0.40%.

[1] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were approximately 0.01% and less than 0.01%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse each class of the Fund to the extent the class's total annual operating expenses exceed the following amounts of the class's average daily net assets: 0.95% for Class II shares, 0.90% for Class III shares, 0.85% for Class IV shares, 0.80% for Class V shares, and 0.77% for Class VI shares. Excluded Fund Fees and Expenses include underlying fund expenses, custodial fees, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] For the period from January 9, 1998 to August 12, 2009, no Class II shares were outstanding. The returns shown in the table for that period are those of Class III shares, which have been adjusted downward to reflect Class II's higher total annual operating expenses (Class II's expenses during these periods were calculated by adjusting Class III's actual total annual operating expenses during such periods upward by the current differential between "Total annual operating expenses" for Class II and Class III shares shown in the Fund's "Annual Fund operating expenses" table).

[2] For the period from October 26, 2004 to February 11, 2005, no Class V shares were outstanding. The returns shown in the table for that period are those of Class IV shares, which have higher expenses.

[1] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.01% and 0.01%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 1.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.75% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, all of a portion of the Fund's custodial fee (up to 10% per annum), independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.01% and 0.01%, respectively.

[1] After reimbursement

[1] For periods prior to the public offering of the Fund's shares, which began on October 29, 2009, the Fund's after-tax returns reflect dividends that included certain non-deductible investment expenses.

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.55% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] For periods prior to the public offering of the Fund's shares, which began on October 29, 2009, the Fund's after-tax returns reflect dividends that included certain non-deductible investment expenses.

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.54% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.54% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.10% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its direct or indirect investment in U.S. Treasury Fund (excluding U.S. Treasury Fund's Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.10% of the Fund's average daily net assets. These contractual expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amounts have been restated to reflect current fees of certain underlying funds.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] "Other expenses" have been restated to reflect current fees.

[3] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.01%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] "Other expenses" have been restated to reflect current fees. The amount includes interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.20% and 0.01%, respectively.

[3] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.03%, 0.01%, and 0.03%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.02%, 0.01%, and less than 0.01%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] "Other expenses" have been restated to reflect current fees.

[3] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.03%, 0.01%, and 0.01%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amount includes interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.11% and 0.01%, respectively.

[3] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.01%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above.

[2] "Other expenses" have been restated to reflect current fees. The amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.09% and 0.06%, respectively.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.05% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. In addition, the Manager has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.05% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without consent by the Fund's Board of Trustees.

[1] After reimbursement

[1] For the period from April 18, 1990 until June 30, 1991, the Fund operated as a money market fund.

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] For periods prior to the public offering of the Fund's shares, which began on October 29, 2009, the Fund's after-tax returns reflect dividends that included certain non-deductible investment expenses.

[1] The amounts reflect the indirect net expenses associated with the Fund's investment in Short-Duration Collateral Fund ("SDCF").

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.05% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. In addition, the Manager has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in SDCF and other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.05% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] As of the date of this Prospectus, no Class VI shares of the Fund have been outstanding since February 27, 2007. The returns shown in the table for that period are those of Class III shares, which have higher expenses than Class VI shares.

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Fund's Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] "Other expenses" have been restated to reflect current fees. These amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were approximately 0.19% and less than 0.01%, respectively.

[3] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.05%, respectively.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.08% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.05% and 0.03%, respectively.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were approximately 0.39% and less than 0.01%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.67% and 0.05%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.61% and 0.02%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.52% and 0.06%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.50% and 0.03%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.48%, less than 0.01%, and 0.05%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation continues through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.49%, less than 0.01%, and 0.05%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.51%, less than 0.01%, and 0.06%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.50% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[2] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, commission fees and purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.43% and 0.01%, respectively.

[1] After reimbursement

[1] The Fund is the successor to GMO U.S. Core Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO U.S. Core Fund and reflects GMO U.S. Core Fund's annual operating expenses (0.02% higher than those of the Fund). As of the date of this Prospectus, no Class V shares of the Fund or its predecessor have been outstanding since February 11, 2005. Class V shares would be invested in the same portfolio of securities as Class III shares. Annual returns would principally differ to the extent Class V shares do not have the same expenses as Class III shares.

[2] The Fund is the successor to GMO Intrinsic Value Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Intrinsic Value Fund and reflects GMO Intrinsic Value Fund's annual operating expenses (0.02% higher than those of the Fund).

[3] The Fund is the successor to GMO Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Growth Fund and reflects GMO Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[4] The Fund is the successor to GMO Small/Mid Cap Value Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Small/Mid Cap Value Fund and reflects GMO Small/Mid Cap Value Fund's annual operating expenses (0.02% higher than those of the Fund).

[5] The Fund is the successor to GMO Small/Mid Cap Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Small/Mid Cap Growth Fund and reflects GMO Small/Mid Cap Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[6] The Fund is the successor to GMO International Disciplined Equity Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO International Disciplined Equity Fund and reflects GMO International Disciplined Equity Fund's annual operating expenses (0.02% higher than those of the Fund).

[7] The Fund is the successor to GMO International Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO International Growth Fund and reflects GMO International Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[8] Information on the Fund's return after taxes is unavailable prior to June 28, 1996, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[9] Information on the Fund's return after taxes is unavailable prior to June 30, 2000, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[10] The Fund's performance during 2001 was positively affected by approximately 7.50% as a result of the Fund's receipt of proceeds from litigation settlements relating to securities held by the Fund during prior periods and accounted for by the Fund during 2001.

[11] The Fund commenced operations on June 28, 1996 with two classes of shares - Class I shares and Class II shares. No Class II shares were outstanding as of October 16, 1996. Class III shares were first issued on October 22, 1996. Class I shares converted to Class III shares on January 9, 1998. Class III performance information presented in the table represents Class II performance from June 28, 1996 to October 16, 1996, Class I performance from October 16, 1996 to October 21, 1996, and Class III performance thereafter. The performance information (before and after taxes) for all periods prior to June 30, 2002 was achieved prior to the change in the Fund's principal investment strategies, effective June 30, 2002.

[12] The Fund's Board of Trustees has approved amendments to the Fund's management agreement and shareholder servicing agreement pursuant to which the Fund would pay the Manager an investment management fee equal to 0.65% of the average daily net assets and a shareholder service fee of 0.15% with respect to the Fund's Class III shares. The Fund currently pays no management or shareholder service fees directly to the Manager, but bears indirectly the management and shareholder service fees charged by the underlying Funds (defined below) in which the Fund invests. Under this new fee arrangement, the Manager would agree to reduce its management and shareholder service fees from the Fund by an amount equal to the management and shareholder service fees received by the Manager from the underlying Funds in respect of the Fund's investments. The new fee arrangements will go into effect only if the amended management agreement is approved by the Fund's shareholders.

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GMO U.S. CORE EQUITY FUND

GMO U.S. CORE EQUITY FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. CORE EQUITY FUND Class M, GMO U.S. Core Equity Fund
Management fee		0.31%
Distribution (12b-1) fee		0.25%
Other expenses		0.03%
Administration fee		0.20%
Total annual operating expenses		0.79%
Expense reimbursement	[1]	(0.03%)
Total annual operating expenses after expense reimbursement		0.76%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO U.S. CORE EQUITY FUND Class M, GMO U.S. Core Equity Fund	Class M	78	[1]	249	436	975

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 96% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class M Shares Years Ending December 31

^[1]

Highest Quarter: 16.57% (2Q2003)

Lowest Quarter: -16.46% (4Q2008)

Year-to-Date (as of 3/31/11): 4.23%

Average Annual Total Returns Periods Ending December 31, 2010

^[1]

Average Annual Total Returns GMO U.S. CORE EQUITY FUND Class M, GMO U.S. Core Equity Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class M	Return Before Taxes		8.58%	0.18%		1.89%	Apr. 15, 2002
Return After Taxes on Distributions	Class M	Return After Taxes on Distributions		8.36%	(0.53%)		1.34%	Apr. 15, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Class M	Return After Taxes on Distributions and Sale of Fund Shares		5.84%	0.07%		1.54%	Apr. 15, 2002
S&P 500 Index	Class M	S&P 500 Index	(reflects no deduction for fees, expenses, or taxes)	15.06%	2.29%		3.54%	Apr. 15, 2002

GMO U.S. GROWTH FUND

GMO U.S. GROWTH FUND

Investment objective

Long-term capital growth.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO U.S. GROWTH FUND Class M, GMO U.S. Growth Fund
Management fee		0.31%
Distribution (12b-1) fee		0.25%
Other expenses	[1]	4.82%
Administration fee		0.20%
Total annual operating expenses		5.58%
Expense reimbursement	[2]	(4.81%)
Total annual operating expenses after expense reimbursement		0.77%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO U.S. GROWTH FUND Class M, GMO U.S. Growth Fund	Class M	79	[1]	1,235	2,378	5,178

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class M Shares Years Ending December 31

^[2]

Highest Quarter: 14.98% (2Q2003)

Lowest Quarter: -16.89% (4Q2008)

Year-to-Date (as of 3/31/11): 4.73%

Average Annual Total Returns Periods Ending December 31, 2010

^[2]

Average Annual Total Returns GMO U.S. GROWTH FUND Class M, GMO U.S. Growth Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class M	Return Before Taxes		13.54%	0.99%		4.24%	Sep. 11, 2002
Return After Taxes on Distributions	Class M	Return After Taxes on Distributions		13.40%	0.62%		3.65%	Sep. 11, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Class M	Return After Taxes on Distributions and Sale of Fund Shares		8.97%	0.82%		3.53%	Sep. 11, 2002
Russell 1000 Growth Index	Class M	Russell 1000 Growth Index	(reflects no deduction for fees, expenses, or taxes)	16.71%	3.75%		6.43%	Sep. 11, 2002

GMO INTERNATIONAL INTRINSIC VALUE FUND

GMO INTERNATIONAL INTRINSIC VALUE FUND

Investment objective

High total return.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO INTERNATIONAL INTRINSIC VALUE FUND Class M, GMO International Intrinsic Value Fund
Management fee		0.50%
Distribution (12b-1) fee		0.25%
Other expenses		0.05%
Administration fee		0.20%
Total annual operating expenses		1.00%
Expense reimbursement	[1]	(0.05%)
Total annual operating expenses after expense reimbursement		0.95%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO INTERNATIONAL INTRINSIC VALUE FUND Class M, GMO International Intrinsic Value Fund	Class M	97	[1]	313	548	1,220

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Principal investment strategies

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund's use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Fund's), the Fund is subject to the risk that these shareholders will disrupt the Funds operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class M Shares Years Ending December 31

Highest Quarter: 22.37% (2Q2009)

Lowest Quarter: -18.21% (3Q2008)

Year-to-Date (as of 3/31/11): 4.13%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO INTERNATIONAL INTRINSIC VALUE FUND Class M, GMO International Intrinsic Value Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class M	Return Before Taxes		7.28%	1.18%		7.66%	Oct. 02, 2003
Return After Taxes on Distributions	Class M	Return After Taxes on Distributions		7.31%	(0.02%)		6.59%	Oct. 02, 2003
Return After Taxes on Distributions and Sale of Fund Shares	Class M	Return After Taxes on Distributions and Sale of Fund Shares		5.18%	1.12%		6.80%	Oct. 02, 2003
MSCI EAFE Value Index (Fund benchmark)	Class M	MSCI EAFE Value Index (Fund benchmark)	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	3.25%	1.37%		7.92%	Oct. 02, 2003
MSCI EAFE Index	Class M	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%		8.06%	Oct. 02, 2003

GMO FOREIGN FUND

GMO FOREIGN FUND

Investment objective

Total return in excess of its benchmark, the MSCI EAFE Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO FOREIGN FUND Class M, GMO Foreign Fund
Management fee		0.60%
Distribution (12b-1) fee		0.25%
Other expenses		0.06%
Administration fee		0.20%
Total annual operating expenses		1.11%
Expense reimbursement	[1]	(0.06%)
Total annual operating expenses after expense reimbursement		1.05%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO FOREIGN FUND Class M, GMO Foreign Fund	Class M	107	[1]	347	606	1,346

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to non-U.S. countries, including companies that issue equity investments included in the MSCI international developed country universe (the universe of securities from which the MSCI EAFE Index, a developed markets index, is constructed) and companies whose equity investments are traded in the securities markets of the world’s non-developed countries (“emerging countries”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to countries outside the U.S. (see “Name Policies”).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class M Shares Years Ending December 31

Highest Quarter: 21.55% (2Q2009)

Lowest Quarter: -19.19% (3Q2008)

Year-to-Date (as of 3/31/11): 3.87%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO FOREIGN FUND Class M, GMO Foreign Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class M	Return Before Taxes		4.47%	1.30%		7.93%	Jan. 25, 2002
Return After Taxes on Distributions	Class M	Return After Taxes on Distributions		4.33%	0.37%		7.09%	Jan. 25, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Class M	Return After Taxes on Distributions and Sale of Fund Shares		3.36%	1.22%		7.00%	Jan. 25, 2002
MSCI EAFE Index	Class M	MSCI EAFE Index	(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)	7.75%	2.46%		7.31%	Jan. 25, 2002

GMO EMERGING COUNTRIES FUND

GMO EMERGING COUNTRIES FUND

Investment objective

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Annual Fund Operating Expenses		GMO EMERGING COUNTRIES FUND Class M, GMO Emerging Countries Fund
Management fee		0.65%
Distribution (12b-1) fee		0.25%
Other expenses		0.50%
Administration fee		0.20%
Acquired fund fees and expenses (underlying fund expenses)	[1]	0.02%
Total annual operating expenses		1.62%
Expense reimbursement	[2]	(0.15%)
Total annual operating expenses after expense reimbursement (Fund and underlying fund expenses)		1.47%

Example

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example (USD $)	Expense Example, By Year, Column [Text]	1 Year		3 Years	5 Years	10 Years
GMO EMERGING COUNTRIES FUND Class M, GMO Emerging Countries Fund	Class M	150	[1]	496	867	1,909

Portfolio turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 124% of the average value of its portfolio.

Principal investment strategies

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging countries. “Emerging countries” include all countries that are not treated as “developed market countries” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities, and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging countries (see “Name Policies”). In addition to investing in companies tied economically to emerging countries, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors, and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts, and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Principal risks of investing in the Fund

The value of the Fund's shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements, or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation, or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds, or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns/Class M Shares Years Ending December 31

Highest Quarter: 31.00% (2Q2009)

Lowest Quarter: -31.47% (4Q2008)

Year-to-Date (as of 3/31/11): 4.61%

Average Annual Total Returns Periods Ending December 31, 2010

Average Annual Total Returns GMO EMERGING COUNTRIES FUND Class M, GMO Emerging Countries Fund	Column	Label	Index No Deduction For Fees, Expenses, Taxes [Text]	1 Year	5 Years	10 Years	Incept.	Inception Date
Return Before Taxes	Class M	Return Before Taxes		20.01%	9.91%		17.77%	Jul. 09, 2002
Return After Taxes on Distributions	Class M	Return After Taxes on Distributions		20.17%	7.06%		15.17%	Jul. 09, 2002
Return After Taxes on Distributions and Sale of Fund Shares	Class M	Return After Taxes on Distributions and Sale of Fund Shares		13.54%	8.19%		15.37%	Jul. 09, 2002
S&P/IFCI Composite Index	Class M	S&P/IFCI Composite Index	(reflects no deduction for fees, expenses, or taxes)	20.64%	13.87%		19.82%	Jul. 09, 2002

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] "Other expenses" have been restated to reflect current fees.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.01% and 0.01%, respectively.

[2] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 1.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[1] After reimbursement

[1] The Fund is the successor to GMO U.S. Core Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO U.S. Core Fund and reflects GMO U.S. Core Fund's annual operating expenses (0.02% higher than those of the Fund).

[2] The Fund is the successor to GMO Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Growth Fund and reflects GMO Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

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GMO U.S. CORE EQUITY FUND | GMO Trust

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High total return.

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June 30, 2012

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rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 96% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

96.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[1]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 16.59% (2Q2003)

Lowest Quarter: -17.14% (3Q2002)

Year-to-Date (as of 3/31/11): 4.41%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[1]

GMO U.S. CORE EQUITY FUND | GMO Trust, Class M Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. CORE EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 96% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

96.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class M Shares Years Ending December 31

^[2]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 16.57% (2Q2003)

Lowest Quarter: -16.46% (4Q2008)

Year-to-Date (as of 3/31/11): 4.23%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[2]

GMO U.S. CORE EQUITY FUND | Class III, GMO U.S. Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.03%

Total annual operating expenses

rr_ExpensesOverAssets

0.49%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.46%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

47

^[4]

3 Years

rr_ExpenseExampleYear03

154

5 Years

rr_ExpenseExampleYear05

271

10 Years

rr_ExpenseExampleYear10

613

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(7.68%)

2002

rr_AnnualReturn2002

(19.67%)

2003

rr_AnnualReturn2003

26.61%

2004

rr_AnnualReturn2004

9.80%

2005

rr_AnnualReturn2005

3.41%

2006

rr_AnnualReturn2006

9.57%

2007

rr_AnnualReturn2007

1.57%

2008

rr_AnnualReturn2008

(30.29%)

2009

rr_AnnualReturn2009

21.23%

2010

rr_AnnualReturn2010

8.82%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.59%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(17.14%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2002

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.41%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. CORE EQUITY FUND | Class IV, GMO U.S. Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

Other expenses

rr_OtherExpensesOverAssets

0.03%

Total annual operating expenses

rr_ExpensesOverAssets

0.44%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.41%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

42

^[4]

3 Years

rr_ExpenseExampleYear03

138

5 Years

rr_ExpenseExampleYear05

243

10 Years

rr_ExpenseExampleYear10

552

GMO U.S. CORE EQUITY FUND | Class V, GMO U.S. Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class V

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.085%

Other expenses

rr_OtherExpensesOverAssets

0.03%

Total annual operating expenses

rr_ExpensesOverAssets

0.43%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.40%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class V

1 Year

rr_ExpenseExampleYear01

41

^[4]

3 Years

rr_ExpenseExampleYear03

135

5 Years

rr_ExpenseExampleYear05

238

10 Years

rr_ExpenseExampleYear10

539

GMO U.S. CORE EQUITY FUND | Class VI, GMO U.S. Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.03%

Total annual operating expenses

rr_ExpensesOverAssets

0.40%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.37%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

38

^[4]

3 Years

rr_ExpenseExampleYear03

125

5 Years

rr_ExpenseExampleYear05

221

10 Years

rr_ExpenseExampleYear10

502

GMO U.S. CORE EQUITY FUND | Class M, GMO U.S. Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.31%

Distribution (12b-1) fee

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.03%

Administration fee

rr_Component1OtherExpensesOverAssets

0.20%

Total annual operating expenses

rr_ExpensesOverAssets

0.79%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[5]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.76%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class M

1 Year

rr_ExpenseExampleYear01

78

^[4]

3 Years

rr_ExpenseExampleYear03

249

5 Years

rr_ExpenseExampleYear05

436

10 Years

rr_ExpenseExampleYear10

975

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

26.34%

2004

rr_AnnualReturn2004

9.51%

2005

rr_AnnualReturn2005

3.10%

2006

rr_AnnualReturn2006

9.33%

2007

rr_AnnualReturn2007

1.18%

2008

rr_AnnualReturn2008

(30.53%)

2009

rr_AnnualReturn2009

20.94%

2010

rr_AnnualReturn2010

8.58%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.57%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(16.46%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.23%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. CORE EQUITY FUND | Return Before Taxes | Class III, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.82%

5 Years

rr_AverageAnnualReturnYear05

0.46%

10 Years

rr_AverageAnnualReturnYear10

0.88%

Incept.

rr_AverageAnnualReturnSinceInception

10.73%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 18, 1985

GMO U.S. CORE EQUITY FUND | Return Before Taxes | Class IV, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.84%

5 Years

rr_AverageAnnualReturnYear05

0.52%

10 Years

rr_AverageAnnualReturnYear10

0.93%

Incept.

rr_AverageAnnualReturnSinceInception

4.20%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO U.S. CORE EQUITY FUND | Return Before Taxes | Class VI, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.95%

5 Years

rr_AverageAnnualReturnYear05

0.57%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO U.S. CORE EQUITY FUND | Return Before Taxes | Class M, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.58%

5 Years

rr_AverageAnnualReturnYear05

0.18%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.89%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 15, 2002

GMO U.S. CORE EQUITY FUND | Return After Taxes on Distributions | Class III, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

8.55%

5 Years

rr_AverageAnnualReturnYear05

(0.30%)

10 Years

rr_AverageAnnualReturnYear10

0.29%

Incept.

rr_AverageAnnualReturnSinceInception

7.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 18, 1985

GMO U.S. CORE EQUITY FUND | Return After Taxes on Distributions | Class M, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

8.36%

5 Years

rr_AverageAnnualReturnYear05

(0.53%)

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.34%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 15, 2002

GMO U.S. CORE EQUITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.05%

5 Years

rr_AverageAnnualReturnYear05

0.31%

10 Years

rr_AverageAnnualReturnYear10

0.62%

Incept.

rr_AverageAnnualReturnSinceInception

8.11%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 18, 1985

GMO U.S. CORE EQUITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class M, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.84%

5 Years

rr_AverageAnnualReturnYear05

0.07%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 15, 2002

GMO U.S. CORE EQUITY FUND | S&P 500 Index | Class III, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

1.41%

Incept.

rr_AverageAnnualReturnSinceInception

10.52%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 18, 1985

GMO U.S. CORE EQUITY FUND | S&P 500 Index | Class IV, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

1.41%

Incept.

rr_AverageAnnualReturnSinceInception

4.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO U.S. CORE EQUITY FUND | S&P 500 Index | Class VI, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.55%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO U.S. CORE EQUITY FUND | S&P 500 Index | Class M, GMO U.S. Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 15, 2002

GMO TOBACCO-FREE CORE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO TOBACCO-FREE CORE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 87% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

87.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund's investment objective by investing primarily in U.S. equities or groups of U.S. equities that the Manager believes will provide higher returns than the S&P 500 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets, and expects to invest substantially all of its assets, in investments in tobacco-free companies (see “Name Policies”). For these purposes, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts, and the term “tobacco-free companies” refers to companies that are not listed in the Tobacco Producing Issuer industry classification maintained by Ford Investor Services.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 15.80% (2Q2003)

Lowest Quarter: -17.27% (3Q2002)

Year-to-Date (as of 3/31/11): 4.43%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO TOBACCO-FREE CORE FUND | Class III, GMO Tobacco-Free Core Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.53%

Total annual operating expenses

rr_ExpensesOverAssets

1.01%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.53%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.48%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

49

^[4]

3 Years

rr_ExpenseExampleYear03

271

5 Years

rr_ExpenseExampleYear05

511

10 Years

rr_ExpenseExampleYear10

1,199

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(8.82%)

2002

rr_AnnualReturn2002

(20.25%)

2003

rr_AnnualReturn2003

26.52%

2004

rr_AnnualReturn2004

9.26%

2005

rr_AnnualReturn2005

2.35%

2006

rr_AnnualReturn2006

9.99%

2007

rr_AnnualReturn2007

1.65%

2008

rr_AnnualReturn2008

(28.66%)

2009

rr_AnnualReturn2009

23.80%

2010

rr_AnnualReturn2010

9.28%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.80%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(17.27%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2002

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.43%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO TOBACCO-FREE CORE FUND | Return Before Taxes | Class III, GMO Tobacco-Free Core Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.28%

5 Years

rr_AverageAnnualReturnYear05

1.53%

10 Years

rr_AverageAnnualReturnYear10

1.05%

Incept.

rr_AverageAnnualReturnSinceInception

8.97%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 31, 1991

GMO TOBACCO-FREE CORE FUND | Return After Taxes on Distributions | Class III, GMO Tobacco-Free Core Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.03%

5 Years

rr_AverageAnnualReturnYear05

0.72%

10 Years

rr_AverageAnnualReturnYear10

0.41%

Incept.

rr_AverageAnnualReturnSinceInception

6.49%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 31, 1991

GMO TOBACCO-FREE CORE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Tobacco-Free Core Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.33%

5 Years

rr_AverageAnnualReturnYear05

1.21%

10 Years

rr_AverageAnnualReturnYear10

0.74%

Incept.

rr_AverageAnnualReturnSinceInception

6.60%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 31, 1991

GMO TOBACCO-FREE CORE FUND | S&P 500 Index | Class III, GMO Tobacco-Free Core Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

1.41%

Incept.

rr_AverageAnnualReturnSinceInception

8.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 31, 1991

GMO QUALITY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO QUALITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

32.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes to be of high quality.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In assessing a company’s quality, the Manager may consider several factors, including in particular, high return on equity, low debt to equity and the Manager’s assessment of the company relative to its competitors.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund may hold fewer than 100 stocks. The Fund may make tactical allocations of up to 20% of its net assets to investments in cash and high quality debt instruments.

The Fund is permitted to invest directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to any country in the world, including emerging countries. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Focused Investment Risk – Focusing investments in a limited number of countries, sectors or companies or in industries with high positive correlations to one another creates additional risk. The Fund invests its assets in the securities of a limited number of issuers, and a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund invested in the securities of a larger number of issuers.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Funds foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance. Performance information (before and after taxes) for certain periods reflects performance achieved prior to the change in the Fund’s principal investment strategies, effective June 1, 2009.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 11.53% (3Q2010)

Lowest Quarter: -13.13% (4Q2008)

Year-to-Date (as of 3/31/11): 3.48%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO QUALITY FUND | Class III, GMO Quality Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.02%

Total annual operating expenses

rr_ExpensesOverAssets

0.50%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.48%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

49

^[4]

3 Years

rr_ExpenseExampleYear03

158

5 Years

rr_ExpenseExampleYear05

278

10 Years

rr_ExpenseExampleYear10

626

Annual Total Returns

rr_BarChartTableAbstract

2005

rr_AnnualReturn2005

(0.90%)

2006

rr_AnnualReturn2006

12.74%

2007

rr_AnnualReturn2007

6.01%

2008

rr_AnnualReturn2008

(24.12%)

2009

rr_AnnualReturn2009

19.85%

2010

rr_AnnualReturn2010

5.47%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.53%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(13.13%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.48%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO QUALITY FUND | Class IV, GMO Quality Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.105%

Other expenses

rr_OtherExpensesOverAssets

0.02%

Total annual operating expenses

rr_ExpensesOverAssets

0.46%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.44%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

45

^[4]

3 Years

rr_ExpenseExampleYear03

146

5 Years

rr_ExpenseExampleYear05

256

10 Years

rr_ExpenseExampleYear10

577

GMO QUALITY FUND | Class V, GMO Quality Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class V

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.085%

Other expenses

rr_OtherExpensesOverAssets

0.02%

Total annual operating expenses

rr_ExpensesOverAssets

0.44%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.42%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class V

1 Year

rr_ExpenseExampleYear01

43

^[4]

3 Years

rr_ExpenseExampleYear03

139

5 Years

rr_ExpenseExampleYear05

244

10 Years

rr_ExpenseExampleYear10

553

GMO QUALITY FUND | Class VI, GMO Quality Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.02%

Total annual operating expenses

rr_ExpensesOverAssets

0.41%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.39%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

40

^[4]

3 Years

rr_ExpenseExampleYear03

130

5 Years

rr_ExpenseExampleYear05

228

10 Years

rr_ExpenseExampleYear10

516

GMO QUALITY FUND | Return Before Taxes | Class III, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.47%

5 Years

rr_AverageAnnualReturnYear05

2.77%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | Return Before Taxes | Class IV, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.51%

5 Years

rr_AverageAnnualReturnYear05

2.80%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.35%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | Return Before Taxes | Class V, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class V

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.53%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.75%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 08, 2006

GMO QUALITY FUND | Return Before Taxes | Class VI, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.57%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 08, 2006

GMO QUALITY FUND | Return After Taxes on Distributions | Class III, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

5.17%

5 Years

rr_AverageAnnualReturnYear05

2.44%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.02%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.91%

5 Years

rr_AverageAnnualReturnYear05

2.41%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | S&P 500 Index | Class III, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | S&P 500 Index | Class IV, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Feb. 06, 2004

GMO QUALITY FUND | S&P 500 Index | Class V, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class V

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(0.65%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 08, 2006

GMO QUALITY FUND | S&P 500 Index | Class VI, GMO Quality Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(0.65%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 08, 2006

GMO U.S. INTRINSIC VALUE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. INTRINSIC VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Long-term capital growth.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 53% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

53.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[7]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 19.25% (2Q2003)

Lowest Quarter: -18.29% (4Q2008)

Year-to-Date (as of 3/31/11): 9.10%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[7]

GMO U.S. INTRINSIC VALUE FUND | Class III, GMO U.S. Intrinsic Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

1.30%

Total annual operating expenses

rr_ExpensesOverAssets

1.76%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(1.30%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.46%

Example

rr_ExpenseExampleAbstract

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

Class III

1 Year

rr_ExpenseExampleYear01

47

^[4]

3 Years

rr_ExpenseExampleYear03

427

5 Years

rr_ExpenseExampleYear05

832

10 Years

rr_ExpenseExampleYear10

1,965

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

3.31%

2002

rr_AnnualReturn2002

(15.75%)

2003

rr_AnnualReturn2003

29.68%

2004

rr_AnnualReturn2004

12.76%

2005

rr_AnnualReturn2005

5.98%

2006

rr_AnnualReturn2006

13.50%

2007

rr_AnnualReturn2007

(3.87%)

2008

rr_AnnualReturn2008

(33.80%)

2009

rr_AnnualReturn2009

20.50%

2010

rr_AnnualReturn2010

11.59%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.25%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(18.29%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

9.10%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. INTRINSIC VALUE FUND | Return Before Taxes | Class III, GMO U.S. Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

11.59%

5 Years

rr_AverageAnnualReturnYear05

(0.58%)

10 Years

rr_AverageAnnualReturnYear10

2.74%

Incept.

rr_AverageAnnualReturnSinceInception

3.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 02, 1999

GMO U.S. INTRINSIC VALUE FUND | Return After Taxes on Distributions | Class III, GMO U.S. Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

11.31%

5 Years

rr_AverageAnnualReturnYear05

(1.79%)

10 Years

rr_AverageAnnualReturnYear10

1.43%

Incept.

rr_AverageAnnualReturnSinceInception

1.99%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 02, 1999

GMO U.S. INTRINSIC VALUE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

7.82%

5 Years

rr_AverageAnnualReturnYear05

(0.65%)

10 Years

rr_AverageAnnualReturnYear10

2.05%

Incept.

rr_AverageAnnualReturnSinceInception

2.46%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 02, 1999

GMO U.S. INTRINSIC VALUE FUND | Russell 1000 Value Index | Class III, GMO U.S. Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 1000 Value Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.51%

5 Years

rr_AverageAnnualReturnYear05

1.28%

10 Years

rr_AverageAnnualReturnYear10

3.26%

Incept.

rr_AverageAnnualReturnSinceInception

3.27%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 02, 1999

GMO U.S. GROWTH FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Long-term capital growth.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

61.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[8]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 15.03% (2Q2003)

Lowest Quarter: -21.46% (1Q2001)

Year-to-Date (as of 3/31/11): 4.78%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[8]

GMO U.S. GROWTH FUND | GMO Trust, Class M Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Long-term capital growth.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

“Other expenses” have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

61.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 1000 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to the U.S. (see “Name Policies”). The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class M Shares Years Ending December 31

^[8]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 14.98% (2Q2003)

Lowest Quarter: -16.89% (4Q2008)

Year-to-Date (as of 3/31/11): 4.73%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[8]

GMO U.S. GROWTH FUND | Class III, GMO U.S. Growth Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

4.82%

^[9]

Total annual operating expenses

rr_ExpensesOverAssets

5.28%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(4.81%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.47%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

48

^[4]

3 Years

rr_ExpenseExampleYear03

1,149

5 Years

rr_ExpenseExampleYear05

2,243

10 Years

rr_ExpenseExampleYear10

4,953

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(20.60%)

2002

rr_AnnualReturn2002

(22.58%)

2003

rr_AnnualReturn2003

28.58%

2004

rr_AnnualReturn2004

5.09%

2005

rr_AnnualReturn2005

4.37%

2006

rr_AnnualReturn2006

2.38%

2007

rr_AnnualReturn2007

5.86%

2008

rr_AnnualReturn2008

(30.90%)

2009

rr_AnnualReturn2009

25.04%

2010

rr_AnnualReturn2010

13.94%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.03%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(21.46%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2001

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.78%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. GROWTH FUND | Class M, GMO U.S. Growth Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.31%

Distribution (12b-1) fee

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

4.82%

^[9]

Administration fee

rr_Component1OtherExpensesOverAssets

0.20%

Total annual operating expenses

rr_ExpensesOverAssets

5.58%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(4.81%)

^[10]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.77%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class M

1 Year

rr_ExpenseExampleYear01

79

^[4]

3 Years

rr_ExpenseExampleYear03

1,235

5 Years

rr_ExpenseExampleYear05

2,378

10 Years

rr_ExpenseExampleYear10

5,178

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

28.21%

2004

rr_AnnualReturn2004

4.80%

2005

rr_AnnualReturn2005

4.06%

2006

rr_AnnualReturn2006

2.05%

2007

rr_AnnualReturn2007

5.56%

2008

rr_AnnualReturn2008

(31.12%)

2009

rr_AnnualReturn2009

24.71%

2010

rr_AnnualReturn2010

13.54%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.98%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(16.89%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.73%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. GROWTH FUND | Return Before Taxes | Class III, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.94%

5 Years

rr_AverageAnnualReturnYear05

1.31%

10 Years

rr_AverageAnnualReturnYear10

(0.78%)

Incept.

rr_AverageAnnualReturnSinceInception

9.58%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 1988

GMO U.S. GROWTH FUND | Return Before Taxes | Class M, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.54%

5 Years

rr_AverageAnnualReturnYear05

0.99%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

4.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 11, 2002

GMO U.S. GROWTH FUND | Return After Taxes on Distributions | Class III, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

13.75%

5 Years

rr_AverageAnnualReturnYear05

0.88%

10 Years

rr_AverageAnnualReturnYear10

(1.31%)

Incept.

rr_AverageAnnualReturnSinceInception

5.35%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 1988

GMO U.S. GROWTH FUND | Return After Taxes on Distributions | Class M, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

13.40%

5 Years

rr_AverageAnnualReturnYear05

0.62%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.65%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 11, 2002

GMO U.S. GROWTH FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

9.29%

5 Years

rr_AverageAnnualReturnYear05

1.08%

10 Years

rr_AverageAnnualReturnYear10

(0.80%)

Incept.

rr_AverageAnnualReturnSinceInception

6.23%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 1988

GMO U.S. GROWTH FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class M, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

8.97%

5 Years

rr_AverageAnnualReturnYear05

0.82%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.53%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 11, 2002

GMO U.S. GROWTH FUND | Russell 1000 Growth Index | Class III, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 1000 Growth Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

16.71%

5 Years

rr_AverageAnnualReturnYear05

3.75%

10 Years

rr_AverageAnnualReturnYear10

0.02%

Incept.

rr_AverageAnnualReturnSinceInception

9.04%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 30, 1988

GMO U.S. GROWTH FUND | Russell 1000 Growth Index | Class M, GMO U.S. Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Russell 1000 Growth Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

16.71%

5 Years

rr_AverageAnnualReturnYear05

3.75%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 11, 2002

GMO U.S. SMALL/MID CAP VALUE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. SMALL/MID CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Long-term capital growth.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 106% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

106.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 2500 Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of U.S. companies that issue stocks included in the Russell 2500 Index, a U.S. stock index, and in companies with similar market capitalizations (“small- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments in small- and mid-cap companies tied economically to the U.S. (see “Name Policies”). As of May 31, 2011, the market capitalization of companies that issue stocks included in the Russell 2500 Index ranged from approximately $11.9 million to $11.7 billion, with an average market capitalization of approximately $3.1 billion and a median market capitalization of approximately $2.8 billion. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[11]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 23.22% (2Q2003)

Lowest Quarter: -20.74% (4Q2008)

Year-to-Date (as of 3/31/11): 8.05%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[11]

GMO U.S. SMALL/MID CAP VALUE FUND | Class III, GMO U.S. Small/Mid Cap Value Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

1.77%

^[9]

Total annual operating expenses

rr_ExpensesOverAssets

2.23%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(1.76%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.47%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

150

^[4]

3 Years

rr_ExpenseExampleYear03

630

5 Years

rr_ExpenseExampleYear05

1,136

10 Years

rr_ExpenseExampleYear10

2,531

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

98

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

575

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,078

10 Years

rr_ExpenseExampleNoRedemptionYear10

2,464

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

9.91%

2002

rr_AnnualReturn2002

(11.48%)

2003

rr_AnnualReturn2003

45.26%

2004

rr_AnnualReturn2004

20.80%

2005

rr_AnnualReturn2005

8.03%

2006

rr_AnnualReturn2006

10.86%

2007

rr_AnnualReturn2007

(12.55%)

2008

rr_AnnualReturn2008

(26.97%)

2009

rr_AnnualReturn2009

14.29%

2010

rr_AnnualReturn2010

25.15%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

23.22%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(20.74%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

8.05%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. SMALL/MID CAP VALUE FUND | Return Before Taxes | Class III, GMO U.S. Small/Mid Cap Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

24.89%

5 Years

rr_AverageAnnualReturnYear05

0.21%

10 Years

rr_AverageAnnualReturnYear10

6.42%

Incept.

rr_AverageAnnualReturnSinceInception

10.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1991

GMO U.S. SMALL/MID CAP VALUE FUND | Return After Taxes on Distributions | Class III, GMO U.S. Small/Mid Cap Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

24.71%

5 Years

rr_AverageAnnualReturnYear05

(0.78%)

10 Years

rr_AverageAnnualReturnYear10

4.04%

Incept.

rr_AverageAnnualReturnSinceInception

7.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1991

GMO U.S. SMALL/MID CAP VALUE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Small/Mid Cap Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

15.96%

5 Years

rr_AverageAnnualReturnYear05

(0.03%)

10 Years

rr_AverageAnnualReturnYear10

4.79%

Incept.

rr_AverageAnnualReturnSinceInception

8.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1991

GMO U.S. SMALL/MID CAP VALUE FUND | Russell 2500 Value Index (Fund benchmark) | Class III, GMO U.S. Small/Mid Cap Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 2500 Value Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

24.82%

5 Years

rr_AverageAnnualReturnYear05

3.85%

10 Years

rr_AverageAnnualReturnYear10

8.53%

Incept.

rr_AverageAnnualReturnSinceInception

11.90%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1991

GMO U.S. SMALL/MID CAP VALUE FUND | Russell 2500 Value + Index (Composite index) | Class III, GMO U.S. Small/Mid Cap Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 2500 Value + Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

24.82%

5 Years

rr_AverageAnnualReturnYear05

3.85%

10 Years

rr_AverageAnnualReturnYear10

8.53%

Incept.

rr_AverageAnnualReturnSinceInception

11.28%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1991

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Russell 2500 Value + Index

GMO U.S. SMALL/MID CAP GROWTH FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. SMALL/MID CAP GROWTH FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Long-term capital growth.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

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The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

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Expense Example [Heading]

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Example

Expense Example Narrative [Text Block]

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This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

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Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

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Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 136% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

136.00%

Strategy [Heading]

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Principal investment strategies

Strategy Narrative [Text Block]

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The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 2500 Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of U.S. companies that issue stocks included in the Russell 2500 Index, a U.S. stock index, and in companies with similar market capitalizations (“small- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments in small- and mid-cap companies tied economically to the U.S. (see “Name Policies”). As of May 31, 2011, the market capitalization of companies that issue stocks included in the Russell 2500 Index ranged from approximately $11.9 million to $11.7 billion, with an average market capitalization of approximately $3.1 billion and a median market capitalization of approximately $2.8 billion. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

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Principal risks of investing in the Fund

Risk Narrative [Text Block]

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The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

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Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

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The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

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Performance

Performance Narrative [Text Block]

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The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

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Bar Chart [Heading]

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Annual Total Returns/Class III Shares Years Ending December 31

^[12]

Bar Chart Closing [Text Block]

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Highest Quarter: 22.74% (2Q2003)

Lowest Quarter: -27.98% (4Q2008)

Year-to-Date (as of 3/31/11): 14.43%

Average Annual Total Returns

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Performance Table Heading

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Average Annual Total Returns Periods Ending December 31, 2010

^[12]

GMO U.S. SMALL/MID CAP GROWTH FUND | Class III, GMO U.S. Small/Mid Cap Growth Fund

Shareholder fees

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Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.31%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

2.73%

^[9]

Total annual operating expenses

rr_ExpensesOverAssets

3.19%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(2.72%)

^[3]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.47%

Example

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Expense Example, By Year, Column [Text]

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Class III

1 Year

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150

^[4]

3 Years

rr_ExpenseExampleYear03

827

5 Years

rr_ExpenseExampleYear05

1,530

10 Years

rr_ExpenseExampleYear10

3,400

Expense Example, No Redemption

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Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

98

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

773

5 Years

rr_ExpenseExampleNoRedemptionYear05

1,474

10 Years

rr_ExpenseExampleNoRedemptionYear10

3,339

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(13.27%)

2002

rr_AnnualReturn2002

(17.62%)

2003

rr_AnnualReturn2003

47.09%

2004

rr_AnnualReturn2004

14.41%

2005

rr_AnnualReturn2005

10.44%

2006

rr_AnnualReturn2006

7.14%

2007

rr_AnnualReturn2007

2.87%

2008

rr_AnnualReturn2008

(41.95%)

2009

rr_AnnualReturn2009

24.03%

2010

rr_AnnualReturn2010

33.40%

Highest Quarterly Return, Label

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Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.74%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

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Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(27.98%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

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Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

14.43%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. SMALL/MID CAP GROWTH FUND | Return Before Taxes | Class III, GMO U.S. Small/Mid Cap Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

32.07%

5 Years

rr_AverageAnnualReturnYear05

0.94%

10 Years

rr_AverageAnnualReturnYear10

3.36%

Incept.

rr_AverageAnnualReturnSinceInception

5.60%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

GMO U.S. SMALL/MID CAP GROWTH FUND | Return After Taxes on Distributions | Class III, GMO U.S. Small/Mid Cap Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

32.00%

5 Years

rr_AverageAnnualReturnYear05

(0.64%)

10 Years

rr_AverageAnnualReturnYear10

1.89%

Incept.

rr_AverageAnnualReturnSinceInception

0.75%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

GMO U.S. SMALL/MID CAP GROWTH FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Small/Mid Cap Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

20.46%

5 Years

rr_AverageAnnualReturnYear05

0.36%

10 Years

rr_AverageAnnualReturnYear10

2.45%

Incept.

rr_AverageAnnualReturnSinceInception

2.35%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

GMO U.S. SMALL/MID CAP GROWTH FUND | Russell 2500 Growth Index | Class III, GMO U.S. Small/Mid Cap Growth Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 2500 Growth Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

28.86%

5 Years

rr_AverageAnnualReturnYear05

5.63%

10 Years

rr_AverageAnnualReturnYear10

4.19%

Incept.

rr_AverageAnnualReturnSinceInception

6.22%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1996

GMO REAL ESTATE FUND | GMO Trust

Risk/Return:

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Risk/Return [Heading]

rr_RiskReturnHeading

GMO REAL ESTATE FUND

Objective [Heading]

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Investment objective

Objective Primary [Text Block]

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High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

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Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

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Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 25% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

25.00%

Strategy [Heading]

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Principal investment strategies

Strategy Narrative [Text Block]

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The Manager seeks to achieve the Fund’s investment objective by investing in investments or groups of investments that the Manager believes will provide higher returns than the MSCI U.S. REIT Index.

The Manager uses active investment management methods, which means that investments are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting investments for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify investments that the Manager believes present positive return potential relative to other investments. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an investment or a group of investments. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an investment or group of investments relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

As a substitute for direct investments, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund has a fundamental policy to concentrate its investments in real estate-related investments. Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in real estate investment trusts (“REITs”) and other real estate-related investments (see “Name Policies”). REITs are managed vehicles that invest in real estate or real estate-related investments (both equity and fixed income securities). For purposes of this Prospectus, the term “real estate-related investments” includes securities of REITs and of companies that derive at least 50% of their revenues and profits from, or have at least 50% of their assets invested in, (i) the development, construction, management, or sale of real estate or (ii) real estate holdings.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Strategy Portfolio Concentration [Text]

rr_StrategyPortfolioConcentration

The Fund has a fundamental policy to concentrate its investments in real estate-related investments.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended (the “1940 Act”), and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Real Estate Risk – Real estate-related investments may decline in value as a result of factors affecting the real estate industry, such as the supply of real property in particular markets, changes in zoning laws, delays in completion of construction, changes in real estate values, changes in property taxes, levels of occupancy, adequacy of rent to cover operating expenses, and local and regional market conditions. The value of real estate-related investments also may be affected by changes in interest rates and social and economic trends. REITs are subject to the risk of fluctuations in income from underlying real estate assets, their inability to manage effectively the cash flows generated by those assets, prepayments and defaults by borrowers, and failing to qualify for the special tax treatment granted to REITs under the Internal Revenue Code of 1986 and/or to maintain exempt status under the 1940 Act.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Models that have demonstrated an ability to explain prior market data often fail to accurately predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Focused Investment Risk – Focusing investments in sectors and industries with high positive correlations to one another creates additional risk. The Fund’s concentration in real estate-related investments make the Fund’s net asset value more susceptible to economic, market, political and other developments affecting the real estate industry.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended (the “1940 Act”), and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Fund’s benchmark, which more accurately reflects the Fund’s investments. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Fund’s benchmark, which more accurately reflects the Fund’s investments.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 32.69% (3Q2009)

Lowest Quarter: -35.42% (4Q2008)

Year-to-Date (as of 3/31/11): 6.58%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO REAL ESTATE FUND | Class III, GMO Real Estate Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.58%

Total annual operating expenses

rr_ExpensesOverAssets

1.06%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.58%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.48%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

49

^[4]

3 Years

rr_ExpenseExampleYear03

282

5 Years

rr_ExpenseExampleYear05

533

10 Years

rr_ExpenseExampleYear10

1,252

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

9.71%

2002

rr_AnnualReturn2002

2.17%

2003

rr_AnnualReturn2003

33.85%

2004

rr_AnnualReturn2004

30.43%

2005

rr_AnnualReturn2005

11.29%

2006

rr_AnnualReturn2006

35.30%

2007

rr_AnnualReturn2007

(17.15%)

2008

rr_AnnualReturn2008

(33.17%)

2009

rr_AnnualReturn2009

24.54%

2010

rr_AnnualReturn2010

27.40%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

32.69%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(35.42%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

6.58%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO REAL ESTATE FUND | Return Before Taxes | Class III, GMO Real Estate Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

27.40%

5 Years

rr_AverageAnnualReturnYear05

3.52%

10 Years

rr_AverageAnnualReturnYear10

9.98%

Incept.

rr_AverageAnnualReturnSinceInception

9.34%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 1996

GMO REAL ESTATE FUND | Return After Taxes on Distributions | Class III, GMO Real Estate Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

25.92%

5 Years

rr_AverageAnnualReturnYear05

(0.12%)

10 Years

rr_AverageAnnualReturnYear10

6.85%

Incept.

rr_AverageAnnualReturnSinceInception

6.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 1996

GMO REAL ESTATE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Real Estate Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

17.68%

5 Years

rr_AverageAnnualReturnYear05

1.57%

10 Years

rr_AverageAnnualReturnYear10

7.47%

Incept.

rr_AverageAnnualReturnSinceInception

6.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 1996

GMO REAL ESTATE FUND | MSCI U.S. REIT Index (Fund benchmark) | Class III, GMO Real Estate Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI U.S. REIT Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

28.48%

5 Years

rr_AverageAnnualReturnYear05

2.99%

10 Years

rr_AverageAnnualReturnYear10

10.57%

Incept.

rr_AverageAnnualReturnSinceInception

10.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 1996

GMO REAL ESTATE FUND | S&P 500 Index | Class III, GMO Real Estate Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P 500 Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

15.06%

5 Years

rr_AverageAnnualReturnYear05

2.29%

10 Years

rr_AverageAnnualReturnYear10

1.41%

Incept.

rr_AverageAnnualReturnSinceInception

6.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

S&P 500 Index

GMO TAX-MANAGED U.S. EQUITIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO TAX-MANAGED U.S. EQUITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High after-tax total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 70% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

70.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the Russell 3000 Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, industry and sector exposure, and market capitalization.

The Manager considers the tax effects of a proposed trade in conjunction with the return forecast of the identified equities, and their potential contribution to the overall portfolio. The Manager also may consider the Fund’s realized and unrealized gains and losses, and current market conditions, because these factors also influence the decision to buy or sell securities.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. There can be no assurance that the Fund’s tax management strategies will be effective, and you may incur tax liabilities that exceed your economic return. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Models that have demonstrated an ability to explain prior market data often fail to accurately predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares (Before Tax) Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 16.69% (2Q2003)

Lowest Quarter: -17.54% (3Q2002)

Year-to-Date (as of 3/31/11): 3.92%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO TAX-MANAGED U.S. EQUITIES FUND | Class III, GMO Tax-Managed U.S. Equities Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.33%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.56%

Total annual operating expenses

rr_ExpensesOverAssets

1.04%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.56%)

^[6]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.48%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

49

^[4]

3 Years

rr_ExpenseExampleYear03

277

5 Years

rr_ExpenseExampleYear05

524

10 Years

rr_ExpenseExampleYear10

1,231

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(9.77%)

2002

rr_AnnualReturn2002

(19.69%)

2003

rr_AnnualReturn2003

25.18%

2004

rr_AnnualReturn2004

9.17%

2005

rr_AnnualReturn2005

4.54%

2006

rr_AnnualReturn2006

10.04%

2007

rr_AnnualReturn2007

2.61%

2008

rr_AnnualReturn2008

(30.78%)

2009

rr_AnnualReturn2009

19.73%

2010

rr_AnnualReturn2010

8.81%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.69%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(17.54%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2002

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.92%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO TAX-MANAGED U.S. EQUITIES FUND | Return Before Taxes | Class III, GMO Tax-Managed U.S. Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

8.81%

5 Years

rr_AverageAnnualReturnYear05

0.36%

10 Years

rr_AverageAnnualReturnYear10

0.53%

Incept.

rr_AverageAnnualReturnSinceInception

2.71%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 1998

GMO TAX-MANAGED U.S. EQUITIES FUND | Return After Taxes on Distributions | Class III, GMO Tax-Managed U.S. Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

8.54%

5 Years

rr_AverageAnnualReturnYear05

0.07%

10 Years

rr_AverageAnnualReturnYear10

0.22%

Incept.

rr_AverageAnnualReturnSinceInception

2.36%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 1998

GMO TAX-MANAGED U.S. EQUITIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Tax-Managed U.S. Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.05%

5 Years

rr_AverageAnnualReturnYear05

0.30%

10 Years

rr_AverageAnnualReturnYear10

0.37%

Incept.

rr_AverageAnnualReturnSinceInception

2.22%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 1998

GMO TAX-MANAGED U.S. EQUITIES FUND | Russell 3000 Index (Fund benchmark) | Class III, GMO Tax-Managed U.S. Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 3000 Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

16.93%

5 Years

rr_AverageAnnualReturnYear05

2.74%

10 Years

rr_AverageAnnualReturnYear10

2.16%

Incept.

rr_AverageAnnualReturnSinceInception

3.25%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 1998

GMO TAX-MANAGED U.S. EQUITIES FUND | Russell 3000 + Index (Composite index) | Class III, GMO Tax-Managed U.S. Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 3000 + Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

16.93%

5 Years

rr_AverageAnnualReturnYear05

2.77%

10 Years

rr_AverageAnnualReturnYear10

1.65%

Incept.

rr_AverageAnnualReturnSinceInception

2.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 1998

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Russell 3000 + Index

GMO INTERNATIONAL CORE EQUITY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL CORE EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[13]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 22.30% (2Q2009)

Lowest Quarter: -19.92% (3Q2008)

Year-to-Date (as of 3/31/11): 3.48%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[13]

GMO INTERNATIONAL CORE EQUITY FUND | Class III, GMO International Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.38%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.58%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[14]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.53%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

54

^[4]

3 Years

rr_ExpenseExampleYear03

181

5 Years

rr_ExpenseExampleYear05

319

10 Years

rr_ExpenseExampleYear10

721

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

37.67%

2004

rr_AnnualReturn2004

22.39%

2005

rr_AnnualReturn2005

14.55%

2006

rr_AnnualReturn2006

24.78%

2007

rr_AnnualReturn2007

11.01%

2008

rr_AnnualReturn2008

(40.05%)

2009

rr_AnnualReturn2009

21.06%

2010

rr_AnnualReturn2010

10.29%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.30%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(19.92%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.48%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL CORE EQUITY FUND | Class IV, GMO International Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.38%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.09%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.52%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[14]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.47%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

48

^[4]

3 Years

rr_ExpenseExampleYear03

162

5 Years

rr_ExpenseExampleYear05

286

10 Years

rr_ExpenseExampleYear10

648

GMO INTERNATIONAL CORE EQUITY FUND | Class VI, GMO International Core Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.38%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.49%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[14]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.44%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

45

^[4]

3 Years

rr_ExpenseExampleYear03

152

5 Years

rr_ExpenseExampleYear05

269

10 Years

rr_ExpenseExampleYear10

611

GMO INTERNATIONAL CORE EQUITY FUND | Return Before Taxes | Class III, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

10.29%

5 Years

rr_AverageAnnualReturnYear05

2.09%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

8.65%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 29, 2002

GMO INTERNATIONAL CORE EQUITY FUND | Return Before Taxes | Class IV, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

10.34%

5 Years

rr_AverageAnnualReturnYear05

2.15%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO INTERNATIONAL CORE EQUITY FUND | Return Before Taxes | Class VI, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

10.39%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.59%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 28, 2006

GMO INTERNATIONAL CORE EQUITY FUND | Return After Taxes on Distributions | Class III, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

10.11%

5 Years

rr_AverageAnnualReturnYear05

1.28%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 29, 2002

GMO INTERNATIONAL CORE EQUITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

7.28%

5 Years

rr_AverageAnnualReturnYear05

1.73%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.50%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 29, 2002

GMO INTERNATIONAL CORE EQUITY FUND | MSCI EAFE Index | Class III, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 29, 2002

GMO INTERNATIONAL CORE EQUITY FUND | MSCI EAFE Index | Class IV, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.32%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO INTERNATIONAL CORE EQUITY FUND | MSCI EAFE Index | Class VI, GMO International Core Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 28, 2006

GMO INTERNATIONAL INTRINSIC VALUE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL INTRINSIC VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After tax returns are shown for Class III Shares only; after tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After tax returns are shown for Class III Shares only; after tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 22.40% (2Q2009)

Lowest Quarter: -18.13% (3Q2008)

Year-to-Date (as of 3/31/11): 4.16%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL INTRINSIC VALUE FUND | GMO Trust, Class M Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL INTRINSIC VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. The term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund's use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Fund's), the Fund is subject to the risk that these shareholders will disrupt the Funds operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class M Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 22.37% (2Q2009)

Lowest Quarter: -18.21% (3Q2008)

Year-to-Date (as of 3/31/11): 4.13%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL INTRINSIC VALUE FUND | Class II, GMO International Intrinsic Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class II

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.22%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.77%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[15]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.72%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class II

1 Year

rr_ExpenseExampleYear01

74

^[4]

3 Years

rr_ExpenseExampleYear03

241

5 Years

rr_ExpenseExampleYear05

423

10 Years

rr_ExpenseExampleYear10

949

GMO INTERNATIONAL INTRINSIC VALUE FUND | Class III, GMO International Intrinsic Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.70%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[15]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.65%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

66

^[4]

3 Years

rr_ExpenseExampleYear03

219

5 Years

rr_ExpenseExampleYear05

385

10 Years

rr_ExpenseExampleYear10

866

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(12.11%)

2002

rr_AnnualReturn2002

(0.59%)

2003

rr_AnnualReturn2003

43.51%

2004

rr_AnnualReturn2004

25.27%

2005

rr_AnnualReturn2005

14.26%

2006

rr_AnnualReturn2006

25.33%

2007

rr_AnnualReturn2007

9.89%

2008

rr_AnnualReturn2008

(38.78%)

2009

rr_AnnualReturn2009

18.65%

2010

rr_AnnualReturn2010

7.59%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.40%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(18.13%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.16%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL INTRINSIC VALUE FUND | Class IV, GMO International Intrinsic Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.09%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.64%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[15]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.59%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

60

^[4]

3 Years

rr_ExpenseExampleYear03

200

5 Years

rr_ExpenseExampleYear05

352

10 Years

rr_ExpenseExampleYear10

794

GMO INTERNATIONAL INTRINSIC VALUE FUND | Class M, GMO International Intrinsic Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.50%

Distribution (12b-1) fee

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Administration fee

rr_Component1OtherExpensesOverAssets

0.20%

Total annual operating expenses

rr_ExpensesOverAssets

1.00%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[16]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.95%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class M

1 Year

rr_ExpenseExampleYear01

97

^[4]

3 Years

rr_ExpenseExampleYear03

313

5 Years

rr_ExpenseExampleYear05

548

10 Years

rr_ExpenseExampleYear10

1,220

Annual Total Returns

rr_BarChartTableAbstract

2004

rr_AnnualReturn2004

24.91%

2005

rr_AnnualReturn2005

13.92%

2006

rr_AnnualReturn2006

24.95%

2007

rr_AnnualReturn2007

9.59%

2008

rr_AnnualReturn2008

(38.96%)

2009

rr_AnnualReturn2009

18.23%

2010

rr_AnnualReturn2010

7.28%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.37%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(18.21%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.13%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return Before Taxes | Class II, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.53%

5 Years

rr_AverageAnnualReturnYear05

1.41%

10 Years

rr_AverageAnnualReturnYear10

6.73%

Incept.

rr_AverageAnnualReturnSinceInception

6.98%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 26, 1996

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return Before Taxes | Class III, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.59%

5 Years

rr_AverageAnnualReturnYear05

1.48%

10 Years

rr_AverageAnnualReturnYear10

6.80%

Incept.

rr_AverageAnnualReturnSinceInception

8.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 31, 1987

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return Before Taxes | Class IV, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.61%

5 Years

rr_AverageAnnualReturnYear05

1.54%

10 Years

rr_AverageAnnualReturnYear10

6.88%

Incept.

rr_AverageAnnualReturnSinceInception

7.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return Before Taxes | Class M, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.28%

5 Years

rr_AverageAnnualReturnYear05

1.18%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 02, 2003

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return After Taxes on Distributions | Class III, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

7.58%

5 Years

rr_AverageAnnualReturnYear05

0.24%

10 Years

rr_AverageAnnualReturnYear10

5.72%

Incept.

rr_AverageAnnualReturnSinceInception

6.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 31, 1987

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return After Taxes on Distributions | Class M, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

7.31%

5 Years

rr_AverageAnnualReturnYear05

(0.02%)

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.59%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 02, 2003

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.43%

5 Years

rr_AverageAnnualReturnYear05

1.36%

10 Years

rr_AverageAnnualReturnYear10

5.84%

Incept.

rr_AverageAnnualReturnSinceInception

6.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 31, 1987

GMO INTERNATIONAL INTRINSIC VALUE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class M, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.18%

5 Years

rr_AverageAnnualReturnYear05

1.12%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 02, 2003

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Value Index (Fund benchmark) | Class II, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Value Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

3.25%

5 Years

rr_AverageAnnualReturnYear05

1.37%

10 Years

rr_AverageAnnualReturnYear10

4.19%

Incept.

rr_AverageAnnualReturnSinceInception

5.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 26, 1996

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Value Index (Fund benchmark) | Class III, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Value Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

3.25%

5 Years

rr_AverageAnnualReturnYear05

1.37%

10 Years

rr_AverageAnnualReturnYear10

4.19%

Incept.

rr_AverageAnnualReturnSinceInception

7.27%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 31, 1987

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Value Index (Fund benchmark) | Class IV, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Value Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

3.25%

5 Years

rr_AverageAnnualReturnYear05

1.37%

10 Years

rr_AverageAnnualReturnYear10

4.19%

Incept.

rr_AverageAnnualReturnSinceInception

6.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Value Index (Fund benchmark) | Class M, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Value Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

3.25%

5 Years

rr_AverageAnnualReturnYear05

1.37%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.92%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 02, 2003

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Index | Class II, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

4.67%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 26, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Index | Class III, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

5.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 31, 1987

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Index | Class IV, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

5.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO INTERNATIONAL INTRINSIC VALUE FUND | MSCI EAFE Index | Class M, GMO International Intrinsic Value Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

8.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 02, 2003

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

The amounts represent an annualized estimate of the Fund’s operating expenses for its initial fiscal year.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Value Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. companies that issue stocks included in the MSCI Standard Indices, international stock indices, and in companies with similar market capitalizations (“large- and mid-cap companies”). Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of large- and mid-cap companies (see “Name Policies”). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S. and include both developed and emerging countries. For purposes of the Fund’s investments, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND | Class III, GMO International Large/Mid Cap Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.80%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[15],[17]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.66%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

82

3 Years

rr_ExpenseExampleYear03

255

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND | Class IV, GMO International Large/Mid Cap Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.09%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.74%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[15],[17]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.60%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

76

3 Years

rr_ExpenseExampleYear03

237

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND | Class V, International Large/Mid Cap Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class V

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.085%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.74%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[15],[17]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.60%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class V

1 Year

rr_ExpenseExampleYear01

76

3 Years

rr_ExpenseExampleYear03

237

GMO INTERNATIONAL LARGE/MID CAP VALUE FUND | Class VI, GMO International Large/Mid Cap Value Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.71%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[15],[17]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.57%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

73

3 Years

rr_ExpenseExampleYear03

227

GMO INTERNATIONAL GROWTH EQUITY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL GROWTH EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 59% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

59.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Growth Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. The Fund may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[18]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 17.83% (3Q2010)

Lowest Quarter: -19.33% (3Q2008)

Year-to-Date (as of 3/31/11): 1.77%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[18]

GMO INTERNATIONAL GROWTH EQUITY FUND | Class III, GMO International Growth Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.70%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[15]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.65%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

66

^[4]

3 Years

rr_ExpenseExampleYear03

221

5 Years

rr_ExpenseExampleYear05

389

10 Years

rr_ExpenseExampleYear10

877

Annual Total Returns

rr_BarChartTableAbstract

2002

rr_AnnualReturn2002

(10.52%)

2003

rr_AnnualReturn2003

30.40%

2004

rr_AnnualReturn2004

20.03%

2005

rr_AnnualReturn2005

13.13%

2006

rr_AnnualReturn2006

24.07%

2007

rr_AnnualReturn2007

13.88%

2008

rr_AnnualReturn2008

(36.72%)

2009

rr_AnnualReturn2009

22.11%

2010

rr_AnnualReturn2010

14.02%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

17.83%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(19.33%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.77%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL GROWTH EQUITY FUND | Class IV, GMO International Growth Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.09%

Other expenses

rr_OtherExpensesOverAssets

0.05%

Total annual operating expenses

rr_ExpensesOverAssets

0.64%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.05%)

^[15]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.59%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

60

^[4]

3 Years

rr_ExpenseExampleYear03

202

5 Years

rr_ExpenseExampleYear05

356

10 Years

rr_ExpenseExampleYear10

805

GMO INTERNATIONAL GROWTH EQUITY FUND | Return Before Taxes | Class III, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

14.02%

5 Years

rr_AverageAnnualReturnYear05

4.48%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

8.02%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2001

GMO INTERNATIONAL GROWTH EQUITY FUND | Return Before Taxes | Class IV, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

14.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.28%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 12, 2006

GMO INTERNATIONAL GROWTH EQUITY FUND | Return After Taxes on Distributions | Class III, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

14.02%

5 Years

rr_AverageAnnualReturnYear05

2.88%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2001

GMO INTERNATIONAL GROWTH EQUITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

9.49%

5 Years

rr_AverageAnnualReturnYear05

3.55%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.77%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2001

GMO INTERNATIONAL GROWTH EQUITY FUND | MSCI EAFE Growth Index (Fund benchmark) | Class III, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Growth Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

12.25%

5 Years

rr_AverageAnnualReturnYear05

3.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.28%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2001

GMO INTERNATIONAL GROWTH EQUITY FUND | MSCI EAFE Growth Index (Fund benchmark) | Class IV, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Growth Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

12.25%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 12, 2006

GMO INTERNATIONAL GROWTH EQUITY FUND | MSCI EAFE Index | Class III, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.73%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 30, 2001

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO INTERNATIONAL GROWTH EQUITY FUND | MSCI EAFE Index | Class IV, GMO International Growth Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 12, 2006

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO DEVELOPED WORLD STOCK FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO DEVELOPED WORLD STOCK FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 34% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

34.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in stocks or groups of stocks that the Manager believes will provide higher returns than the MSCI World Index.

The Manager uses active investment management methods, which means that stocks are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting stocks for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify stocks that the Manager believes present positive return potential relative to other stocks. Some of these methods evaluate individual stocks or a group of stocks (e.g., stocks of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of a stock or a group of stocks. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of a stock or group of stocks relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in stocks, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through underlying funds or derivatives) at least 80% of its assets in stocks tied economically to developed markets (see “Name Policies”). For this purpose, the term “stocks” refers to investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts, and the term “developed markets” refers to those countries included in the MSCI World Index, a global developed markets equity index, and countries with similar characteristics (e.g., countries that have sustained economic development, sufficient liquidity for listed companies and accessible markets). The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 18.37% (2Q2009)

Lowest Quarter: -19.92% (4Q2008)

Year-to-Date (as of 3/31/11): 4.62%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO DEVELOPED WORLD STOCK FUND | Class III, GMO Developed World Stock Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.25%

^[19]

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.25%

^[19]

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.45%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual operating expenses

rr_ExpensesOverAssets

0.71%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[20]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.60%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

112

^[4]

3 Years

rr_ExpenseExampleYear03

269

5 Years

rr_ExpenseExampleYear05

439

10 Years

rr_ExpenseExampleYear10

933

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

86

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

240

5 Years

rr_ExpenseExampleNoRedemptionYear05

408

10 Years

rr_ExpenseExampleNoRedemptionYear10

895

Annual Total Returns

rr_BarChartTableAbstract

2006

rr_AnnualReturn2006

20.98%

2007

rr_AnnualReturn2007

7.24%

2008

rr_AnnualReturn2008

(37.58%)

2009

rr_AnnualReturn2009

22.79%

2010

rr_AnnualReturn2010

10.37%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.37%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(19.92%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.62%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO DEVELOPED WORLD STOCK FUND | Class IV, GMO Developed World Stock Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.25%

^[19]

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.25%

^[19]

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.45%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual operating expenses

rr_ExpensesOverAssets

0.66%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[20]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.55%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

107

^[4]

3 Years

rr_ExpenseExampleYear03

253

5 Years

rr_ExpenseExampleYear05

412

10 Years

rr_ExpenseExampleYear10

873

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

81

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

225

5 Years

rr_ExpenseExampleNoRedemptionYear05

381

10 Years

rr_ExpenseExampleNoRedemptionYear10

835

GMO DEVELOPED WORLD STOCK FUND | Return Before Taxes | Class III, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.82%

5 Years

rr_AverageAnnualReturnYear05

1.78%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.64%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 01, 2005

GMO DEVELOPED WORLD STOCK FUND | Return Before Taxes | Class IV, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.93%

5 Years

rr_AverageAnnualReturnYear05

1.83%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.51%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 01, 2005

GMO DEVELOPED WORLD STOCK FUND | Return After Taxes on Distributions | Class III, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.30%

5 Years

rr_AverageAnnualReturnYear05

0.85%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.76%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 01, 2005

GMO DEVELOPED WORLD STOCK FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.64%

5 Years

rr_AverageAnnualReturnYear05

1.31%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 01, 2005

GMO DEVELOPED WORLD STOCK FUND | MSCI World Index | Class III, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

2.43%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.38%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 01, 2005

GMO DEVELOPED WORLD STOCK FUND | MSCI World Index | Class IV, GMO Developed World Stock Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

2.43%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.17%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 01, 2005

GMO INTERNATIONAL SMALL COMPANIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL SMALL COMPANIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

“Other expenses” have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund's investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Small Cap Index.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. small companies. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies (see “Name Policies”). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S., and include both developed and emerging companies (“Non-U.S. Companies”). The Manager considers “small companies” to be all Non-U.S. Companies other than (i) the largest 500 companies in developed countries based on full, non-float adjusted market capitalization and (ii) any company in an emerging country with a full, non-float adjusted market capitalization that is greater than or equal to that of the smallest excluded developed country companies. A company’s full, non-float adjusted market capitalization includes all of the company’s outstanding equity securities. As of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company included within the Fund’s definition of small companies was approximately $8.3 billion. For purposes of the Fund’s investments, the term “equities” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 32.07% (2Q2009)

Lowest Quarter: -21.15% (3Q2008)

Year-to-Date (as of 3/31/11): 1.71%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL SMALL COMPANIES FUND | Class III, GMO International Small Companies Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.60%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.13%

^[9]

Total annual operating expenses

rr_ExpensesOverAssets

0.88%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

^[21]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.75%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

178

^[4]

3 Years

rr_ExpenseExampleYear03

373

5 Years

rr_ExpenseExampleYear05

583

10 Years

rr_ExpenseExampleYear10

1,192

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

126

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

316

5 Years

rr_ExpenseExampleNoRedemptionYear05

523

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,117

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(6.70%)

2002

rr_AnnualReturn2002

(1.25%)

2003

rr_AnnualReturn2003

67.44%

2004

rr_AnnualReturn2004

27.04%

2005

rr_AnnualReturn2005

24.66%

2006

rr_AnnualReturn2006

27.36%

2007

rr_AnnualReturn2007

7.63%

2008

rr_AnnualReturn2008

(42.37%)

2009

rr_AnnualReturn2009

33.44%

2010

rr_AnnualReturn2010

21.18%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

32.07%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter"

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(21.15%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.71%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL SMALL COMPANIES FUND | Return Before Taxes | Class III, GMO International Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

19.97%

5 Years

rr_AverageAnnualReturnYear05

4.81%

10 Years

rr_AverageAnnualReturnYear10

11.94%

Incept.

rr_AverageAnnualReturnSinceInception

9.83%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 14, 1991

GMO INTERNATIONAL SMALL COMPANIES FUND | Return After Taxes on Distributions | Class III, GMO International Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

19.52%

5 Years

rr_AverageAnnualReturnYear05

1.91%

10 Years

rr_AverageAnnualReturnYear10

9.08%

Incept.

rr_AverageAnnualReturnSinceInception

7.53%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 14, 1991

GMO INTERNATIONAL SMALL COMPANIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

13.01%

5 Years

rr_AverageAnnualReturnYear05

3.46%

10 Years

rr_AverageAnnualReturnYear10

9.78%

Incept.

rr_AverageAnnualReturnSinceInception

7.86%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 14, 1991

GMO INTERNATIONAL SMALL COMPANIES FUND | MSCI EAFE Small Cap Index (Fund benchmark) | Class III, GMO International Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Small Cap Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deductions for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

22.04%

5 Years

rr_AverageAnnualReturnYear05

2.81%

10 Years

rr_AverageAnnualReturnYear10

9.45%

Incept.

rr_AverageAnnualReturnSinceInception

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 14, 1991

GMO INTERNATIONAL SMALL COMPANIES FUND | MSCI EAFE Small Cap + Index (Composite index) | Class III, GMO International Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Small Cap + Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

22.04%

5 Years

rr_AverageAnnualReturnYear05

5.70%

10 Years

rr_AverageAnnualReturnYear10

9.56%

Incept.

rr_AverageAnnualReturnSinceInception

7.20%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 14, 1991

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Small Cap + Index

GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

The amounts represent an annualized estimate of the Fund’s operating expenses for its initial fiscal year.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund's operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund's performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund's portfolio turnover rate is not available.

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager pursues the Fund's investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund's strategic direction.

The Manager typically seeks to achieve the Fund's investment objective by investing in equities or groups of equities of non-U.S. small companies.

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager's evaluation of companies' published financial information, securities' prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund's investment universe. The Manager also may adjust the Fund's portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter ("OTC") derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund's investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of non-U.S. small companies. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies (see "Name Policies"). For these purposes, non-U.S. companies are companies tied economically to countries other than the U.S., and include both developed and emerging companies ("Non-U.S. Companies"). The Manager considers “small companies” to be all Non-U.S. Companies other than (i) the largest 500 companies in developed countries based on full, non-float adjusted market capitalization and (ii) any company in an emerging country with a full, non-float adjusted market capitalization that is greater than or equal to that of the smallest excluded developed country companies. A company's full, non-float adjusted market capitalization includes all of the company's outstanding equity securities. As of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company included within the Fund's definition of small companies was approximately $8.3 billion. For purposes of the Fund's investments, the term "equities" refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO ASSET ALLOCATION INTERNATIONAL SMALL COMPANIES FUND | Class III, GMO Asset Allocation International Small Companies Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.60%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.14%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.89%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[17],[21]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.75%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

192

3 Years

rr_ExpenseExampleYear03

389

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

140

3 Years

rr_ExpenseExampleNoRedemptionYear03

332

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

High after-tax total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 40% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

40.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager seeks to achieve the Fund’s investment objective by investing in equities or groups of equities that the Manager believes will provide higher returns than the MSCI EAFE Index (after tax).

The Manager uses active investment management methods, which means that equities are bought and sold according to the Manager’s evaluation of companies’ published financial information, securities’ prices, equity and bond markets, and the overall economy.

In selecting equities for the Fund, the Manager may use a combination of quantitative and qualitative investment methods to identify equities that the Manager believes present positive return potential relative to other equities. Some of these methods evaluate individual equities or a group of equities (e.g., equities of companies in a particular industry) based on the ratio of their price to historical financial information, including book value, cash flow and earnings, and forecasted financial information provided by industry analysts. The Manager may compare these ratios to industry or market averages in assessing the relative attractiveness of an equity or a group of equities. Other methods used by the Manager focus on evaluating patterns of price movement or volatility of an equity or group of equities relative to the Fund’s investment universe. The Manager also may adjust the Fund’s portfolio for factors such as position size, market capitalization, and exposure to groups such as industry, sector, country or currency.

The Manager considers the tax effects of a proposed trade in conjunction with the return forecast of the identified equities, and their potential contribution to the overall portfolio. The Manager also may consider the Fund’s realized and unrealized gains and losses, and current market conditions, because these factors also influence the decision to buy or sell securities.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include futures, options, forward currency contracts and swap contracts. In addition, the Fund may lend its portfolio securities.

The Fund typically invests directly and indirectly (e.g., through underlying funds or derivatives) in equities of companies tied economically to countries other than the U.S. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The terms “equities” and “equity investments” refer to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Manager may make investments tied economically to emerging countries. These investments generally will represent 15% or less of the Fund’s total assets.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. There can be no assurance that the Fund’s tax management strategies will be effective, and you may incur tax liabilities that exceed your economic return. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is computed by the Manager) and a broad-based international stock index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is computed by the Manager) and a broad-based international stock index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares (Before Tax) Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 21.51% (2Q2009)

Lowest Quarter: -20.34% (3Q2008)

Year-to-Date (as of 3/31/11): 4.05%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | Class III, GMO Tax-Managed International Equities Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual operating expenses

rr_ExpensesOverAssets

0.76%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[22]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.65%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

66

^[4]

3 Years

rr_ExpenseExampleYear03

232

5 Years

rr_ExpenseExampleYear05

412

10 Years

rr_ExpenseExampleYear10

932

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(8.71%)

2002

rr_AnnualReturn2002

(2.33%)

2003

rr_AnnualReturn2003

41.05%

2004

rr_AnnualReturn2004

24.44%

2005

rr_AnnualReturn2005

16.76%

2006

rr_AnnualReturn2006

25.42%

2007

rr_AnnualReturn2007

13.42%

2008

rr_AnnualReturn2008

(39.20%)

2009

rr_AnnualReturn2009

20.98%

2010

rr_AnnualReturn2010

9.49%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

21.51%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(20.34%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.05%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | Return Before Taxes | Class III, GMO Tax-Managed International Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.49%

5 Years

rr_AverageAnnualReturnYear05

2.76%

10 Years

rr_AverageAnnualReturnYear10

7.67%

Incept.

rr_AverageAnnualReturnSinceInception

7.10%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1998

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | Return After Taxes on Distributions | Class III, GMO Tax-Managed International Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.30%

5 Years

rr_AverageAnnualReturnYear05

1.99%

10 Years

rr_AverageAnnualReturnYear10

6.98%

Incept.

rr_AverageAnnualReturnSinceInception

6.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1998

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Tax-Managed International Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.82%

5 Years

rr_AverageAnnualReturnYear05

2.57%

10 Years

rr_AverageAnnualReturnYear10

6.76%

Incept.

rr_AverageAnnualReturnSinceInception

6.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1998

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | MSCI EAFE Index (after tax) (Fund benchmark) | Class III, GMO Tax-Managed International Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index (after tax) (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

6.85%

5 Years

rr_AverageAnnualReturnYear05

1.55%

10 Years

rr_AverageAnnualReturnYear10

2.88%

Incept.

rr_AverageAnnualReturnSinceInception

3.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1998

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index (after tax)

GMO TAX-MANAGED INTERNATIONAL EQUITIES FUND | MSCI EAFE Index | Class III, GMO Tax-Managed International Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

3.74%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1998

GMO FOREIGN FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO FOREIGN FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the MSCI EAFE Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to non-U.S. countries, including companies that issue equity investments included in the MSCI international developed country universe (the universe of securities from which the MSCI EAFE Index, a developed markets index, is constructed) and companies whose equity investments are traded in the securities markets of the world’s non-developed countries (“emerging countries”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to countries outside the U.S. (see “Name Policies”).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Information on the Fund’s return after taxes is unavailable prior to June 28, 1996, the date the Fund commenced operations as a registered investment company. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 21.67% (2Q2009)

Lowest Quarter: -19.12% (3Q2008)

Year-to-Date (as of 3/31/11): 3.95%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[23]

GMO FOREIGN FUND | GMO Trust, Class M Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO FOREIGN FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of its benchmark, the MSCI EAFE Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 55% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

55.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to non-U.S. countries, including companies that issue equity investments included in the MSCI international developed country universe (the universe of securities from which the MSCI EAFE Index, a developed markets index, is constructed) and companies whose equity investments are traded in the securities markets of the world’s non-developed countries (“emerging countries”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to countries outside the U.S. (see “Name Policies”).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Funds performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class M Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 21.55% (2Q2009)

Lowest Quarter: -19.19% (3Q2008)

Year-to-Date (as of 3/31/11): 3.87%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO FOREIGN FUND | Class II, GMO Foreign Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class II

Management fee

rr_ManagementFeesOverAssets

0.60%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.22%

Other expenses

rr_OtherExpensesOverAssets

0.06%

Total annual operating expenses

rr_ExpensesOverAssets

0.88%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

^[21]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.82%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class II

1 Year

rr_ExpenseExampleYear01

84

^[4]

3 Years

rr_ExpenseExampleYear03

275

5 Years

rr_ExpenseExampleYear05

482

10 Years

rr_ExpenseExampleYear10

1,079

GMO FOREIGN FUND | Class III, GMO Foreign Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.60%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.06%

Total annual operating expenses

rr_ExpensesOverAssets

0.81%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

^[21]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.75%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

77

^[4]

3 Years

rr_ExpenseExampleYear03

253

5 Years

rr_ExpenseExampleYear05

444

10 Years

rr_ExpenseExampleYear10

996

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(10.10%)

2002

rr_AnnualReturn2002

(5.74%)

2003

rr_AnnualReturn2003

40.89%

2004

rr_AnnualReturn2004

21.90%

2005

rr_AnnualReturn2005

13.69%

2006

rr_AnnualReturn2006

27.12%

2007

rr_AnnualReturn2007

10.23%

2008

rr_AnnualReturn2008

(39.79%)

2009

rr_AnnualReturn2009

22.46%

2010

rr_AnnualReturn2010

4.77%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

21.67%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(19.12%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.95%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO FOREIGN FUND | Class IV, GMO Foreign Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.60%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.09%

Other expenses

rr_OtherExpensesOverAssets

0.06%

Total annual operating expenses

rr_ExpensesOverAssets

0.75%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

^[21]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.69%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

70

^[4]

3 Years

rr_ExpenseExampleYear03

234

5 Years

rr_ExpenseExampleYear05

411

10 Years

rr_ExpenseExampleYear10

925

GMO FOREIGN FUND | Class M, GMO Foreign Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.60%

Distribution (12b-1) fee

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.06%

Administration fee

rr_Component1OtherExpensesOverAssets

0.20%

Total annual operating expenses

rr_ExpensesOverAssets

1.11%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

^[24]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.05%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class M

1 Year

rr_ExpenseExampleYear01

107

^[4]

3 Years

rr_ExpenseExampleYear03

347

5 Years

rr_ExpenseExampleYear05

606

10 Years

rr_ExpenseExampleYear10

1,346

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

40.33%

2004

rr_AnnualReturn2004

21.68%

2005

rr_AnnualReturn2005

13.29%

2006

rr_AnnualReturn2006

26.77%

2007

rr_AnnualReturn2007

9.91%

2008

rr_AnnualReturn2008

(40.01%)

2009

rr_AnnualReturn2009

22.15%

2010

rr_AnnualReturn2010

4.47%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

21.55%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(19.19%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.87%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO FOREIGN FUND | Return Before Taxes | Class II, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.62%

5 Years

rr_AverageAnnualReturnYear05

1.51%

10 Years

rr_AverageAnnualReturnYear10

5.92%

Incept.

rr_AverageAnnualReturnSinceInception

7.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1996

GMO FOREIGN FUND | Return Before Taxes | Class III, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[25]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.77%

5 Years

rr_AverageAnnualReturnYear05

1.60%

10 Years

rr_AverageAnnualReturnYear10

6.00%

Incept.

rr_AverageAnnualReturnSinceInception

12.68%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 31, 1984

GMO FOREIGN FUND | Return Before Taxes | Class IV, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.82%

5 Years

rr_AverageAnnualReturnYear05

1.63%

10 Years

rr_AverageAnnualReturnYear10

6.06%

Incept.

rr_AverageAnnualReturnSinceInception

7.42%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO FOREIGN FUND | Return Before Taxes | Class M, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.47%

5 Years

rr_AverageAnnualReturnYear05

1.30%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 25, 2002

GMO FOREIGN FUND | Return After Taxes on Distributions | Class III, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[25]

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

4.58%

5 Years

rr_AverageAnnualReturnYear05

0.62%

10 Years

rr_AverageAnnualReturnYear10

5.16%

Incept.

rr_AverageAnnualReturnSinceInception

^[23]

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 31, 1984

GMO FOREIGN FUND | Return After Taxes on Distributions | Class M, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

4.33%

5 Years

rr_AverageAnnualReturnYear05

0.37%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 25, 2002

GMO FOREIGN FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[25]

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.60%

5 Years

rr_AverageAnnualReturnYear05

1.46%

10 Years

rr_AverageAnnualReturnYear10

5.22%

Incept.

rr_AverageAnnualReturnSinceInception

^[23]

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 31, 1984

GMO FOREIGN FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class M, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.36%

5 Years

rr_AverageAnnualReturnYear05

1.22%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 25, 2002

GMO FOREIGN FUND | MSCI EAFE Index | Class II, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

4.64%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1996

GMO FOREIGN FUND | MSCI EAFE Index | Class III, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[25]

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

9.76%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 31, 1984

GMO FOREIGN FUND | MSCI EAFE Index | Class IV, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

5.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO FOREIGN FUND | MSCI EAFE Index | Class M, GMO Foreign Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction of fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 25, 2002

GMO FOREIGN SMALL COMPANIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO FOREIGN SMALL COMPANIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the S&P Developed ex-U.S. Small Cap Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 61% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

61.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to countries other than the U.S. whose outstanding publicly traded equities are in the lowest 25% of available market capitalization (float) in a particular country (“small companies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in securities of small companies that are tied economically to countries outside the U.S. (see “Name Policies”). The market capitalization range of companies whose equity investments are held by the Fund is generally within the market capitalization range of companies in the Fund’s benchmark, which represents the lowest 15% of available market capitalization (float) of the S&P Broad Market Index in each country. Depending on the country, as of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company (in a particular country) included in the S&P Developed ex-U.S. Small Cap Index ranged from approximately $563 million (Greece) to $15.8 billion (Germany). Depending upon the country, as of May 31, 2011, the market capitalization of the outstanding common stock and other stock-related securities of the largest company (in a particular country) included within the Fund’s definition of small companies ranged from approximately $772 million (Greece) to $22 billion (Switzerland) (based on exchange rates as of May 31, 2011).

• Country selection – The Fund’s country selections relative to its benchmark are determined by the Manager’s cumulative quantitative value score for each country together with the Manager’s evaluation of the country’s fundamentals. The Fund typically overweights or underweights (sometimes to a significant extent) its investment exposure in particular countries relative to the Fund’s benchmark.

• Stock selection – The Manager selects stocks using fundamental analysis that is informed by a disciplined quantitative screening process. The Manager analyzes companies for financial, operational and managerial strength and compares them to their global, regional and local industry peers. As part of the investment process, the Manager frequently meets with management and/or visits companies.

The Fund may hold up to 10% of its total assets in cash and cash equivalents to manage cash inflows and outflows as a result of shareholder purchases and redemptions. To the extent the Fund holds cash or cash equivalents to manage shareholder purchases or redemptions, it may not achieve its investment objective. The Fund typically makes investments tied economically to emerging countries, but these investments (excluding investments in companies tied economically to emerging countries included in the Fund’s benchmark) generally represent 10% or less of the Fund’s total assets. In pursuing its investment objective, the Fund may (but is not obligated to) use a wide variety of exchange-traded and over-the-counter (“OTC”) derivatives, including, without limitation, futures and options. The Fund’s foreign currency exposure may differ from the currency exposure of its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Shares of small- and mid-cap companies often have lower trading volumes and a limited number or no market makers. Thus, a large position may limit or prevent the Fund from selling those shares or unwinding derivative positions on them at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Leveraging Risk – The Fund’s use of derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III, tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III, tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 31.25% (2Q2009)

Lowest Quarter: -24.05% (3Q2008)

Year-to-Date (as of 3/31/11): 3.94%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[26]

GMO FOREIGN SMALL COMPANIES FUND | Class III, GMO Foreign Small Companies Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.70%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.14%

Total annual operating expenses

rr_ExpensesOverAssets

0.99%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[27]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.85%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

188

^[4]

3 Years

rr_ExpenseExampleYear03

406

5 Years

rr_ExpenseExampleYear05

641

10 Years

rr_ExpenseExampleYear10

1,318

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

136

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

350

5 Years

rr_ExpenseExampleNoRedemptionYear05

581

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,244

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

3.66%

2002

rr_AnnualReturn2002

2.63%

2003

rr_AnnualReturn2003

50.73%

2004

rr_AnnualReturn2004

29.24%

2005

rr_AnnualReturn2005

19.17%

2006

rr_AnnualReturn2006

35.83%

2007

rr_AnnualReturn2007

7.85%

2008

rr_AnnualReturn2008

(44.68%)

2009

rr_AnnualReturn2009

44.58%

2010

rr_AnnualReturn2010

24.83%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

31.25%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(24.05%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.94%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO FOREIGN SMALL COMPANIES FUND | Class IV, GMO Foreign Small Companies Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.70%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

Other expenses

rr_OtherExpensesOverAssets

0.14%

Total annual operating expenses

rr_ExpensesOverAssets

0.94%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[27]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.80%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

183

^[4]

3 Years

rr_ExpenseExampleYear03

390

5 Years

rr_ExpenseExampleYear05

615

10 Years

rr_ExpenseExampleYear10

1,260

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

131

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

334

5 Years

rr_ExpenseExampleNoRedemptionYear05

554

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,186

GMO FOREIGN SMALL COMPANIES FUND | Return Before Taxes | Class III, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[28]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

23.59%

5 Years

rr_AverageAnnualReturnYear05

7.69%

10 Years

rr_AverageAnnualReturnYear10

13.59%

Incept.

rr_AverageAnnualReturnSinceInception

12.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 04, 1995

GMO FOREIGN SMALL COMPANIES FUND | Return Before Taxes | Class IV, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

^[29]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

23.67%

5 Years

rr_AverageAnnualReturnYear05

7.71%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

13.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 14, 2002

GMO FOREIGN SMALL COMPANIES FUND | Return After Taxes on Distributions | Class III, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[28]

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

23.58%

5 Years

rr_AverageAnnualReturnYear05

5.66%

10 Years

rr_AverageAnnualReturnYear10

11.92%

Incept.

rr_AverageAnnualReturnSinceInception

^[26]

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 04, 1995

GMO FOREIGN SMALL COMPANIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[28]

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

15.29%

5 Years

rr_AverageAnnualReturnYear05

6.21%

10 Years

rr_AverageAnnualReturnYear10

11.75%

Incept.

rr_AverageAnnualReturnSinceInception

^[26]

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 04, 1995

GMO FOREIGN SMALL COMPANIES FUND | S&P Developed ex-U.S. Small Cap Index | Class III, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

^[28]

Label

rr_AverageAnnualReturnLabel

S&P Developed ex-U.S. Small Cap Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

21.96%

5 Years

rr_AverageAnnualReturnYear05

5.16%

10 Years

rr_AverageAnnualReturnYear10

9.28%

Incept.

rr_AverageAnnualReturnSinceInception

7.39%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 04, 1995

GMO FOREIGN SMALL COMPANIES FUND | S&P Developed ex-U.S. Small Cap Index | Class IV, GMO Foreign Small Companies Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

^[29]

Label

rr_AverageAnnualReturnLabel

S&P Developed ex-U.S. Small Cap Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

21.96%

5 Years

rr_AverageAnnualReturnYear05

5.16%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

12.28%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 14, 2002

GMO EMERGING MARKETS FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO EMERGING MARKETS FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 114% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

114.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging markets. “Emerging markets” include all markets that are not treated as “developed markets” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging markets (see “Name Policies”). In addition to investing in companies tied economically to emerging markets, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging markets, the economies of which tend to be more volatile than the economies of developed markets.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 31.90% (2Q2009)

Lowest Quarter: -30.50% (4Q2008)

Year-to-Date (as of 3/31/11): 4.49%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO EMERGING MARKETS FUND | Class II, GMO Emerging Markets Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class II

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

^[30]

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class II

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.22%

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[31]

Total annual operating expenses

rr_ExpensesOverAssets

1.11%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[32]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.08%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class II

1 Year

rr_ExpenseExampleYear01

272

^[4]

3 Years

rr_ExpenseExampleYear03

516

5 Years

rr_ExpenseExampleYear05

780

10 Years

rr_ExpenseExampleYear10

1,534

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class II

1 Year

rr_ExpenseExampleNoRedemptionYear01

189

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

427

5 Years

rr_ExpenseExampleNoRedemptionYear05

684

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,418

GMO EMERGING MARKETS FUND | Class III, GMO Emerging Markets Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

^[30]

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[31]

Total annual operating expenses

rr_ExpensesOverAssets

1.04%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[32]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.03%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

267

^[4]

3 Years

rr_ExpenseExampleYear03

496

5 Years

rr_ExpenseExampleYear05

745

10 Years

rr_ExpenseExampleYear10

1,457

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

184

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

407

5 Years

rr_ExpenseExampleNoRedemptionYear05

648

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,340

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

9.78%

2002

rr_AnnualReturn2002

0.80%

2003

rr_AnnualReturn2003

70.13%

2004

rr_AnnualReturn2004

26.59%

2005

rr_AnnualReturn2005

39.71%

2006

rr_AnnualReturn2006

29.72%

2007

rr_AnnualReturn2007

36.58%

2008

rr_AnnualReturn2008

(55.10%)

2009

rr_AnnualReturn2009

70.59%

2010

rr_AnnualReturn2010

20.51%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

31.90%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(30.50%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.49%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO EMERGING MARKETS FUND | Class IV, GMO Emerging Markets Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

^[30]

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.105%

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[31]

Total annual operating expenses

rr_ExpensesOverAssets

1.00%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[32]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.99%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

263

^[4]

3 Years

rr_ExpenseExampleYear03

484

5 Years

rr_ExpenseExampleYear05

724

10 Years

rr_ExpenseExampleYear10

1,411

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

180

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

395

5 Years

rr_ExpenseExampleNoRedemptionYear05

627

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,294

GMO EMERGING MARKETS FUND | Class V, GMO Emerging Markets Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class V

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class V

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.085%

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[31]

Total annual operating expenses

rr_ExpensesOverAssets

0.98%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[32]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.94%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class V

1 Year

rr_ExpenseExampleYear01

258

^[4]

3 Years

rr_ExpenseExampleYear03

475

5 Years

rr_ExpenseExampleYear05

710

10 Years

rr_ExpenseExampleYear10

1,386

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class V

1 Year

rr_ExpenseExampleNoRedemptionYear01

175

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

386

5 Years

rr_ExpenseExampleNoRedemptionYear05

613

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,268

GMO EMERGING MARKETS FUND | Class VI, GMO Emerging Markets Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class VI

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.13%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[31]

Total annual operating expenses

rr_ExpensesOverAssets

0.95%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[32]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.91%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

255

^[4]

3 Years

rr_ExpenseExampleYear03

466

5 Years

rr_ExpenseExampleYear05

694

10 Years

rr_ExpenseExampleYear10

1,352

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class VI

1 Year

rr_ExpenseExampleNoRedemptionYear01

172

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

376

5 Years

rr_ExpenseExampleNoRedemptionYear05

597

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,233

GMO EMERGING MARKETS FUND | Return Before Taxes | Class II, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

^[33]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

18.55%

5 Years

rr_AverageAnnualReturnYear05

9.91%

10 Years

rr_AverageAnnualReturnYear10

18.18%

Incept.

rr_AverageAnnualReturnSinceInception

11.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 29, 1996

GMO EMERGING MARKETS FUND | Return Before Taxes | Class III, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

18.59%

5 Years

rr_AverageAnnualReturnYear05

9.98%

10 Years

rr_AverageAnnualReturnYear10

18.28%

Incept.

rr_AverageAnnualReturnSinceInception

10.60%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 09, 1993

GMO EMERGING MARKETS FUND | Return Before Taxes | Class IV, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

18.67%

5 Years

rr_AverageAnnualReturnYear05

10.03%

10 Years

rr_AverageAnnualReturnYear10

18.33%

Incept.

rr_AverageAnnualReturnSinceInception

13.92%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO EMERGING MARKETS FUND | Return Before Taxes | Class V, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class V

^[34]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

18.78%

5 Years

rr_AverageAnnualReturnYear05

10.07%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

20.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 04, 2003

GMO EMERGING MARKETS FUND | Return Before Taxes | Class VI, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

18.77%

5 Years

rr_AverageAnnualReturnYear05

10.10%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

20.77%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO EMERGING MARKETS FUND | Return After Taxes on Distributions | Class III, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

18.69%

5 Years

rr_AverageAnnualReturnYear05

7.30%

10 Years

rr_AverageAnnualReturnYear10

16.21%

Incept.

rr_AverageAnnualReturnSinceInception

9.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 09, 1993

GMO EMERGING MARKETS FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

12.01%

5 Years

rr_AverageAnnualReturnYear05

8.15%

10 Years

rr_AverageAnnualReturnYear10

16.06%

Incept.

rr_AverageAnnualReturnSinceInception

8.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 09, 1993

GMO EMERGING MARKETS FUND | S&P/IFCI Composite Index | Class II, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class II

^[33]

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

17.68%

Incept.

rr_AverageAnnualReturnSinceInception

10.11%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 29, 1996

GMO EMERGING MARKETS FUND | S&P/IFCI Composite Index | Class III, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

17.68%

Incept.

rr_AverageAnnualReturnSinceInception

8.12%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 09, 1993

GMO EMERGING MARKETS FUND | S&P/IFCI Composite Index | Class IV, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

17.68%

Incept.

rr_AverageAnnualReturnSinceInception

13.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO EMERGING MARKETS FUND | S&P/IFCI Composite Index | Class V, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class V

^[34]

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

21.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 04, 2003

GMO EMERGING MARKETS FUND | S&P/IFCI Composite Index | Class VI, GMO Emerging Markets Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

22.03%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 2003

GMO EMERGING COUNTRIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO EMERGING COUNTRIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 124% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

124.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging countries. “Emerging countries” include all countries that are not treated as “developed market countries” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging countries (see “Name Policies”). In addition to investing in companies tied economically to emerging countries, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 31.14% (2Q2009)

Lowest Quarter: -31.38% (4Q2008)

Year-to-Date (as of 3/31/11): 4.63%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO EMERGING COUNTRIES FUND | GMO Trust, Class M Shares

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO EMERGING COUNTRIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the S&P/IFCI Composite Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold Class M shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 124% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

124.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies tied economically to emerging countries. “Emerging countries” include all countries that are not treated as “developed market countries” in the MSCI World Index or MSCI EAFE Index. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities, and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to emerging countries (see “Name Policies”). In addition to investing in companies tied economically to emerging countries, the Fund may invest in companies that the Manager believes are likely to benefit from growth in the emerging markets.

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select countries, sectors, and equity investments.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts, and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements, or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation, or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. In addition, the Fund may buy securities that are less liquid than those in its benchmark.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations. The Fund may buy securities that have smaller market capitalizations than those in its benchmark.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Focused Investment Risk – Focusing investments in a limited number of countries and geographic regions creates additional risk.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds, or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Funds performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated (since inception of Class M shares) and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class M Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 31.00% (2Q2009)

Lowest Quarter: -31.47% (4Q2008)

Year-to-Date (as of 3/31/11): 4.61%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO EMERGING COUNTRIES FUND | Class III, GMO Emerging Countries Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.65%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.50%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[35]

Total annual operating expenses

rr_ExpensesOverAssets

1.32%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[36]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.17%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

119

^[4]

3 Years

rr_ExpenseExampleYear03

404

5 Years

rr_ExpenseExampleYear05

709

10 Years

rr_ExpenseExampleYear10

1,577

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

6.03%

2002

rr_AnnualReturn2002

(0.12%)

2003

rr_AnnualReturn2003

69.37%

2004

rr_AnnualReturn2004

27.04%

2005

rr_AnnualReturn2005

36.31%

2006

rr_AnnualReturn2006

29.52%

2007

rr_AnnualReturn2007

37.78%

2008

rr_AnnualReturn2008

(54.93%)

2009

rr_AnnualReturn2009

68.01%

2010

rr_AnnualReturn2010

20.47%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

31.14%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(31.38%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.63%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO EMERGING COUNTRIES FUND | Class M, GMO Emerging Countries Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.65%

Distribution (12b-1) fee

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.50%

Administration fee

rr_Component1OtherExpensesOverAssets

0.20%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[35]

Total annual operating expenses

rr_ExpensesOverAssets

1.62%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.15%)

^[37]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.47%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class M

1 Year

rr_ExpenseExampleYear01

150

^[4]

3 Years

rr_ExpenseExampleYear03

496

5 Years

rr_ExpenseExampleYear05

867

10 Years

rr_ExpenseExampleYear10

1,909

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

68.79%

2004

rr_AnnualReturn2004

26.55%

2005

rr_AnnualReturn2005

35.97%

2006

rr_AnnualReturn2006

29.14%

2007

rr_AnnualReturn2007

37.38%

2008

rr_AnnualReturn2008

(55.12%)

2009

rr_AnnualReturn2009

67.85%

2010

rr_AnnualReturn2010

20.01%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

31.00%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(31.47%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.61%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO EMERGING COUNTRIES FUND | Return Before Taxes | Class III, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

20.47%

5 Years

rr_AverageAnnualReturnYear05

10.23%

10 Years

rr_AverageAnnualReturnYear10

17.59%

Incept.

rr_AverageAnnualReturnSinceInception

11.64%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 29, 1997

GMO EMERGING COUNTRIES FUND | Return Before Taxes | Class M, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

20.01%

5 Years

rr_AverageAnnualReturnYear05

9.91%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

17.77%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 09, 2002

GMO EMERGING COUNTRIES FUND | Return After Taxes on Distributions | Class III, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

20.59%

5 Years

rr_AverageAnnualReturnYear05

7.33%

10 Years

rr_AverageAnnualReturnYear10

15.28%

Incept.

rr_AverageAnnualReturnSinceInception

9.85%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 29, 1997

GMO EMERGING COUNTRIES FUND | Return After Taxes on Distributions | Class M, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

20.17%

5 Years

rr_AverageAnnualReturnYear05

7.06%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

15.17%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 09, 2002

GMO EMERGING COUNTRIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

13.88%

5 Years

rr_AverageAnnualReturnYear05

8.44%

10 Years

rr_AverageAnnualReturnYear10

15.35%

Incept.

rr_AverageAnnualReturnSinceInception

9.97%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 29, 1997

GMO EMERGING COUNTRIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class M, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

13.54%

5 Years

rr_AverageAnnualReturnYear05

8.19%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

15.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 09, 2002

GMO EMERGING COUNTRIES FUND | S&P/IFCI Composite Index | Class III, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

17.68%

Incept.

rr_AverageAnnualReturnSinceInception

10.48%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 29, 1997

GMO EMERGING COUNTRIES FUND | S&P/IFCI Composite Index | Class M, GMO Emerging Countries Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class M

Label

rr_AverageAnnualReturnLabel

S&P/IFCI Composite Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

20.64%

5 Years

rr_AverageAnnualReturnYear05

13.87%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

19.82%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 09, 2002

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO EMERGING DOMESTIC OPPORTUNITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

Acquired Fund Fees and Expenses, Based on Estimates [Text]

rr_AcquiredFundFeesAndExpensesBasedOnEstimates

The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund had not commenced operations as of the fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate is not available.

Strategy [Heading]

rr_StrategyHeading

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies whose prospects are linked to the internal (“domestic”) development and growth of the world's non-developed markets (“emerging markets”), including companies that provide goods and services to emerging market consumers. “Emerging markets” include all markets that are not treated as “developed markets” in the MSCI World Index or MSCI EAFE Index.

The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments related to emerging markets (see “Name Policy”). The Fund’s investments are not limited to investments in companies located in any particular country or geographic region, and may include investments in companies located in developed markets (e.g., the U.S.) that are related to, or whose prospects are linked to, emerging markets. The Fund does not control risk relative to the MSCI Emerging Markets (EM) Index or any other securities index.

The Manager uses fundamental analysis to evaluate and select countries, sectors and companies that it believes are most likely to benefit from domestic growth in emerging markets. In evaluating and selecting investments, the Manager may consider many factors, including the Manager’s assessment of a country’s and/or sector’s fundamentals or growth prospects as well as a company’s positioning relative to its competitors.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal Risks of Investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of value of those investments. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments related to emerging markets, the economies of which tend to be more volatile than the economies of developed markets.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – The Fund’s investments in companies whose prospects are linked to the internal development and growth of emerging markets create additional risk because the performance of those companies is likely to be highly correlated.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security.

The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations. The Fund is also subject to risk because the Fund does not seek to control risk relative to a particular securities market index or benchmark.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds (including ETFs) in which it invests will not perform as expected.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | Class II, GMO Emerging Domestic Opportunities Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class II

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class II

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.22%

Other expenses

rr_OtherExpensesOverAssets

3.55%

^[17]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

4.53%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.45%)

^[17],[38]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.08%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class II

1 Year

rr_ExpenseExampleYear01

610

3 Years

rr_ExpenseExampleYear03

1,518

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class II

1 Year

rr_ExpenseExampleNoRedemptionYear01

530

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,438

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | Class III, GMO Emerging Domestic Opportunities Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

3.55%

^[17]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

4.46%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.45%)

^[17],[38]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

1.01%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

603

3 Years

rr_ExpenseExampleYear03

1,499

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

524

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,418

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | Class IV, GMO Emerging Domestic Opportunities Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.105%

Other expenses

rr_OtherExpensesOverAssets

3.55%

^[17]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

4.42%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.45%)

^[17],[38]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.97%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

600

3 Years

rr_ExpenseExampleYear03

1,488

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

520

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,407

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | Class V, GMO Emerging Domestic Opportunities Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class V

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class V

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.085%

Other expenses

rr_OtherExpensesOverAssets

3.55%

^[17]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

4.40%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.45%)

^[17],[38]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.95%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class V

1 Year

rr_ExpenseExampleYear01

598

3 Years

rr_ExpenseExampleYear03

1,482

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class V

1 Year

rr_ExpenseExampleNoRedemptionYear01

518

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,401

GMO EMERGING DOMESTIC OPPORTUNITIES FUND | Class VI, GMO Emerging Domestic Opportunities Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class VI

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.80%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.80%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.75%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

3.55%

^[17]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

4.37%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(3.45%)

^[17],[38]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.92%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

596

3 Years

rr_ExpenseExampleYear03

1,474

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class VI

1 Year

rr_ExpenseExampleNoRedemptionYear01

515

3 Years

rr_ExpenseExampleNoRedemptionYear03

1,393

GMO TAIWAN FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO TAIWAN FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the MSCI Taiwan Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 129% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

129.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund typically makes equity investments directly and indirectly (e.g., through underlying funds or derivatives) in companies doing business in, or otherwise tied economically to, Taiwan. The Fund may invest in companies of any market capitalization. The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in investments tied economically to Taiwan (see “Name Policies”).

The Manager uses proprietary quantitative techniques and fundamental analysis to evaluate and select sectors and equity investments. In evaluating and selecting investments, the Manager may consider many factors, including the Manager’s assessment of a sector’s fundamentals as well as a company’s positioning relative to its competitors.

The Fund may invest a significant portion of its assets in securities of issuers in industries with high positive correlations to one another (e.g., different industries within broad sectors, such as technology or financial services).

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives and exchange-traded funds (“ETFs”). The Manager also may use derivatives and ETFs: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, warrants, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ from the currency exposure represented by its equity investments. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Because the Fund normally does not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries. Certain characteristics of Taiwan’s economy and geographic location also subject the Fund to risks. For example, Taiwan is a small island state with few raw material resources and limited land area and thus it relies heavily on imports for its commodity needs. Any fluctuations or shortages in the commodity markets could have a negative impact on the Taiwanese economy. Also, rising labor costs and increasing environmental consciousness have led some labor-intensive industries to relocate to countries with cheaper work forces, and continued labor outsourcing may adversely affect the Taiwanese economy. Taiwan’s economy also is intricately linked with economies of other Asian countries, which, like emerging market economies, often experience over-extensions of credit, frequent and pronounced currency fluctuations, devaluations and restrictions, rising unemployment and fluctuations in inflation. Currency devaluations in any one country can have a significant effect on the entire region. Political and social unrest in Asian countries could cause further economic and market uncertainty in Taiwan. In particular, the Taiwanese economy is dependent on the economies of Japan and China, and also the United States, and a reduction in purchases by any of them of Taiwanese products and services or negative changes in their economies would likely have an adverse impact on the Taiwanese economy. Taiwan’s geographic proximity to the People’s Republic of China and Taiwan’s history of political contention with China have resulted in ongoing tensions with China, including the continual risk of war with China. These tensions may materially affect the Taiwanese economy and securities markets. All of these risks could reduce the value of an investment in Taiwan Fund.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments tied economically to Taiwan, creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 22.85% (3Q2010)

Lowest Quarter: -23.74% (4Q2008)

Year-to-Date (as of 3/31/11): -0.04%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO TAIWAN FUND | Class III, GMO Taiwan Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.15%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.45%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.81%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.37%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[35]

Total annual operating expenses

rr_ExpensesOverAssets

1.35%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

199

^[4]

3 Years

rr_ExpenseExampleYear03

492

5 Years

rr_ExpenseExampleYear05

807

10 Years

rr_ExpenseExampleYear10

1,701

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

152

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

442

5 Years

rr_ExpenseExampleNoRedemptionYear05

753

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,636

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

28.84%

2004

rr_AnnualReturn2004

10.24%

2005

rr_AnnualReturn2005

11.89%

2006

rr_AnnualReturn2006

20.41%

2007

rr_AnnualReturn2007

3.95%

2008

rr_AnnualReturn2008

(44.22%)

2009

rr_AnnualReturn2009

73.06%

2010

rr_AnnualReturn2010

24.84%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

22.85%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(23.74%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

(0.04%)

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO TAIWAN FUND | Return Before Taxes | Class III, GMO Taiwan Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

24.09%

5 Years

rr_AverageAnnualReturnYear05

8.44%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

11.12%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 04, 2002

GMO TAIWAN FUND | Return After Taxes on Distributions | Class III, GMO Taiwan Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

^[39]

1 Year

rr_AverageAnnualReturnYear01

23.80%

5 Years

rr_AverageAnnualReturnYear05

6.56%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.72%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 04, 2002

GMO TAIWAN FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Taiwan Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

^[39]

1 Year

rr_AverageAnnualReturnYear01

15.76%

5 Years

rr_AverageAnnualReturnYear05

6.82%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 04, 2002

GMO TAIWAN FUND | MSCI Taiwan Index | Class III, GMO Taiwan Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI Taiwan Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

21.84%

5 Years

rr_AverageAnnualReturnYear05

8.74%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

13.15%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 04, 2002

GMO FLEXIBLE EQUITIES FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO FLEXIBLE EQUITIES FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the MSCI World Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 71% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

71.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund may invest directly and indirectly (e.g., through underlying funds or derivatives) in equity investments traded in any of the world’s securities markets. Under normal circumstances, the Fund invests directly and indirectly at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts. The Fund is permitted to make equity investments of all types, including equity investments issued by foreign and/or U.S. companies, growth and/or value style equities, and equity investments of companies of any market capitalization. In addition, the Fund is not limited in how much it may invest in any market or in the types of equity investments it may pursue, and it may often invest all its assets in a limited number of equity investments of companies in a single country and/or capitalization range. The Fund could experience material losses from a single investment. As of the date of this Prospectus, substantially all of the Fund’s assets were invested in equity investments tied economically to Japan.

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

As a substitute for direct investments in equities, the Manager may use exchange-traded and over-the-counter (“OTC”) derivatives. The Manager also may use derivatives: (i) in an attempt to reduce investment exposures (which may result in a reduction below zero); (ii) in an attempt to adjust elements of the Fund’s investment exposure; and (iii) to effect transactions intended as substitutes for securities lending. Derivatives used may include options, futures, swap contracts and reverse repurchase agreements. The Fund’s foreign currency exposure may differ significantly from the currency exposure represented by its equity investments. For investment and hedging purposes, the Fund also may make short sales of securities, including short sales of securities the Fund does not own. In addition, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark. In addition, the Fund may lend its portfolio securities.

The Fund may identify and measure its performance against one or more secondary benchmarks from time to time. The Fund does not seek to control risk relative to the MSCI World Index or any other benchmark.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk. As noted above, as of the date of this Prospectus, substantially all of the Fund’s assets were invested in equity investments tied economically to Japan.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that the Fund’s loss on a short sale of securities that the Fund does not own is unlimited.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 20.74% (2Q2009)

Lowest Quarter: -24.04% (1Q2009)

Year-to-Date (as of 3/31/11): -0.65%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO FLEXIBLE EQUITIES FUND | Class III, GMO Flexible Equities Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.55%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual operating expenses

rr_ExpensesOverAssets

0.81%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[40]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.70%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

72

^[4]

3 Years

rr_ExpenseExampleYear03

248

5 Years

rr_ExpenseExampleYear05

439

10 Years

rr_ExpenseExampleYear10

991

Annual Total Returns

rr_BarChartTableAbstract

2009

rr_AnnualReturn2009

(10.03%)

2010

rr_AnnualReturn2010

2.22%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

20.74%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(24.04%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2009

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

(0.65%)

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO FLEXIBLE EQUITIES FUND | Class VI, GMO Flexible Equities Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.55%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.11%

Total annual operating expenses

rr_ExpensesOverAssets

0.72%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[40]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.61%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

62

^[4]

3 Years

rr_ExpenseExampleYear03

219

5 Years

rr_ExpenseExampleYear05

390

10 Years

rr_ExpenseExampleYear10

884

GMO FLEXIBLE EQUITIES FUND | Return Before Taxes | Class III, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

2.22%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(1.66%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO FLEXIBLE EQUITIES FUND | Return Before Taxes | Class VI, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

2.27%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(1.56%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO FLEXIBLE EQUITIES FUND | Return After Taxes on Distributions | Class III, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

^[39]

1 Year

rr_AverageAnnualReturnYear01

2.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(1.88%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO FLEXIBLE EQUITIES FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

^[39]

1 Year

rr_AverageAnnualReturnYear01

1.81%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(1.37%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO FLEXIBLE EQUITIES FUND | MSCI World Index | Class III, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

22.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO FLEXIBLE EQUITIES FUND | MSCI World Index | Class VI, GMO Flexible Equities Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

22.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 12, 2008

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the MSCI EAFE Index (Hedged).

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

32.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in other GMO Funds. The Fund may invest in International Core Equity Fund, International Intrinsic Value Fund, International Growth Equity Fund, International Small Companies Fund and Flexible Equities Fund (collectively, the “underlying Funds”). In addition, the Fund may invest in securities directly. Under normal circumstances, the Fund invests directly and indirectly (through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among major sectors in the international equity markets (e.g., large-cap value, large-cap growth, large-cap core, small- and mid-cap value and small- and mid-cap growth) to select the underlying Funds and decide how much to invest in each. The Manager shifts investments among the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments.

The Manager assesses the currency exposure of the underlying Funds’ holdings and then attempts to hedge at least 70% of that exposure relative to the U.S. dollar through the use of currency forwards and other derivatives. While the Fund’s benchmark is fully hedged, the Fund may take active overweighted and underweighted positions in particular currencies relative to its benchmark.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds. The Fund also may lend its portfolio securities.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund’s or the underlying Fund’s performance more than if the Fund or underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund or an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. The Fund or an underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests will not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged by the Fund or an underlying Fund.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Leveraging Risk – The use of derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund’s or the underlying Fund’s performance more than if the Fund or underlying Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark and an additional broad-based international stock index selected by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 16.08% (2Q2003)

Lowest Quarter: -15.63% (3Q2002)

Year-to-Date (as of 3/31/11): 0.43%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | Class III, GMO Currency Hedged International Equity Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.54%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[41]

Other expenses

rr_OtherExpensesOverAssets

0.08%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.58%

Total annual operating expenses

rr_ExpensesOverAssets

1.35%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.65%)

^[41]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.70%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

72

^[4]

3 Years

rr_ExpenseExampleYear03

374

5 Years

rr_ExpenseExampleYear05

699

10 Years

rr_ExpenseExampleYear10

1,619

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(5.27%)

2002

rr_AnnualReturn2002

(14.26%)

2003

rr_AnnualReturn2003

20.96%

2004

rr_AnnualReturn2004

14.77%

2005

rr_AnnualReturn2005

27.32%

2006

rr_AnnualReturn2006

19.31%

2007

rr_AnnualReturn2007

5.88%

2008

rr_AnnualReturn2008

(34.09%)

2009

rr_AnnualReturn2009

16.11%

2010

rr_AnnualReturn2010

7.72%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

16.08%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(15.63%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2002

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

0.43%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | Return Before Taxes | Class III, GMO Currency Hedged International Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.72%

5 Years

rr_AverageAnnualReturnYear05

0.81%

10 Years

rr_AverageAnnualReturnYear10

4.10%

Incept.

rr_AverageAnnualReturnSinceInception

7.65%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 1995

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | Return After Taxes on Distributions | Class III, GMO Currency Hedged International Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

7.72%

5 Years

rr_AverageAnnualReturnYear05

(2.90%)

10 Years

rr_AverageAnnualReturnYear10

0.90%

Incept.

rr_AverageAnnualReturnSinceInception

3.56%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 1995

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Currency Hedged International Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.02%

5 Years

rr_AverageAnnualReturnYear05

3.99%

10 Years

rr_AverageAnnualReturnYear10

4.46%

Incept.

rr_AverageAnnualReturnSinceInception

6.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 1995

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | MSCI EAFE Index (Hedged) (Fund benchmark) | Class III, GMO Currency Hedged International Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index (Hedged) (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

5.60%

5 Years

rr_AverageAnnualReturnYear05

0.07%

10 Years

rr_AverageAnnualReturnYear10

0.59%

Incept.

rr_AverageAnnualReturnSinceInception

5.97%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 1995

GMO CURRENCY HEDGED INTERNATIONAL EQUITY FUND | MSCI EAFE Index | Class III, GMO Currency Hedged International Equity Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

2.46%

10 Years

rr_AverageAnnualReturnYear10

3.50%

Incept.

rr_AverageAnnualReturnSinceInception

5.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 30, 1995

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI EAFE Index

GMO DOMESTIC BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO DOMESTIC BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the Barclays Capital U.S. Government Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amounts have been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 8% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

8.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

Historically, the Fund has implemented its strategies: (i) synthetically by using exchange-traded and over-the-counter (“OTC”) derivatives and investing in other GMO Funds and/or (ii) directly by purchasing bonds. The Fund principally holds shares of Short-Duration Collateral Fund (“SDCF”) (a Fund that primarily holds U.S. asset-backed securities).

The Fund has also invested in and may continue to hold:

• U.S. bonds (including U.S. government bonds, U.S. corporate bonds and asset-backed securities);

• derivatives, including without limitation, futures contracts, reverse repurchase agreements, credit default swaps and other swap contracts;

• shares of U.S. Treasury Fund (for cash management purposes); and

• foreign bonds.

Because of the deterioration in credit markets that became acute in 2008, the Fund, including through its investment in SDCF, currently has and is expected to continue to have material exposure to below investment grade U.S. asset-backed securities (also known as “junk bonds”). The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds tied economically to the U.S. (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 7.29% (3Q2009)

Lowest Quarter: -6.39% (4Q2008)

Year-to-Date (as of 3/31/11): 1.51%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO DOMESTIC BOND FUND | Class III, GMO Domestic Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.10%

^[42]

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[42]

Other expenses

rr_OtherExpensesOverAssets

0.03%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[43]

Total annual operating expenses

rr_ExpensesOverAssets

0.29%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[42]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.26%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

27

^[4]

3 Years

rr_ExpenseExampleYear03

95

5 Years

rr_ExpenseExampleYear05

169

10 Years

rr_ExpenseExampleYear10

388

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

7.44%

2002

rr_AnnualReturn2002

11.85%

2003

rr_AnnualReturn2003

3.83%

2004

rr_AnnualReturn2004

4.41%

2005

rr_AnnualReturn2005

2.92%

2006

rr_AnnualReturn2006

3.69%

2007

rr_AnnualReturn2007

4.96%

2008

rr_AnnualReturn2008

(8.61%)

2009

rr_AnnualReturn2009

19.83%

2010

rr_AnnualReturn2010

9.06%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.29%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(6.39%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.51%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO DOMESTIC BOND FUND | Class VI, GMO Domestic Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.10%

^[42]

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

^[42]

Other expenses

rr_OtherExpensesOverAssets

0.03%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[43]

Total annual operating expenses

rr_ExpensesOverAssets

0.20%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[42]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.17%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

17

^[4]

3 Years

rr_ExpenseExampleYear03

64

5 Years

rr_ExpenseExampleYear05

114

10 Years

rr_ExpenseExampleYear10

264

GMO DOMESTIC BOND FUND | Return Before Taxes | Class III, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.06%

5 Years

rr_AverageAnnualReturnYear05

5.39%

10 Years

rr_AverageAnnualReturnYear10

5.71%

Incept.

rr_AverageAnnualReturnSinceInception

6.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 18, 1994

GMO DOMESTIC BOND FUND | Return Before Taxes | Class VI, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.14%

5 Years

rr_AverageAnnualReturnYear05

5.47%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 26, 2005

GMO DOMESTIC BOND FUND | Return After Taxes on Distributions | Class III, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

8.64%

5 Years

rr_AverageAnnualReturnYear05

3.52%

10 Years

rr_AverageAnnualReturnYear10

3.78%

Incept.

rr_AverageAnnualReturnSinceInception

4.13%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 18, 1994

GMO DOMESTIC BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.88%

5 Years

rr_AverageAnnualReturnYear05

3.51%

10 Years

rr_AverageAnnualReturnYear10

3.63%

Incept.

rr_AverageAnnualReturnSinceInception

4.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 18, 1994

GMO DOMESTIC BOND FUND | Barclays Capital U.S. Government Index | Class III, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Government Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

5.52%

5 Years

rr_AverageAnnualReturnYear05

5.45%

10 Years

rr_AverageAnnualReturnYear10

5.42%

Incept.

rr_AverageAnnualReturnSinceInception

6.34%

Inception Date

rr_AverageAnnualReturnInceptionDate

Aug. 18, 1994

GMO DOMESTIC BOND FUND | Barclays Capital U.S. Government Index | Class VI, GMO Domestic Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Government Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

5.52%

5 Years

rr_AverageAnnualReturnYear05

5.45%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.16%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 26, 2005

GMO CORE PLUS BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO CORE PLUS BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the Barclays Capital U.S. Aggregate Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

“Other expenses” have been restated to reflect current fees.

The amounts have been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 46% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

46.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 5.2 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy.

Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 9.12% (3Q2009)

Lowest Quarter: -15.24% (4Q2008)

Year-to-Date (as of 3/31/11): 1.54%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO CORE PLUS BOND FUND | Class III, GMO Core Plus Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.13%

^[9]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.04%

^[45]

Total annual operating expenses

rr_ExpensesOverAssets

0.57%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.43%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

44

^[4]

3 Years

rr_ExpenseExampleYear03

173

5 Years

rr_ExpenseExampleYear05

313

10 Years

rr_ExpenseExampleYear10

723

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

9.89%

2002

rr_AnnualReturn2002

5.81%

2003

rr_AnnualReturn2003

11.23%

2004

rr_AnnualReturn2004

6.58%

2005

rr_AnnualReturn2005

3.80%

2006

rr_AnnualReturn2006

5.63%

2007

rr_AnnualReturn2007

(1.44%)

2008

rr_AnnualReturn2008

(19.59%)

2009

rr_AnnualReturn2009

21.70%

2010

rr_AnnualReturn2010

13.27%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.12%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(15.24%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.54%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO CORE PLUS BOND FUND | Class IV, GMO Core Plus Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.13%

^[9]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.04%

^[45]

Total annual operating expenses

rr_ExpensesOverAssets

0.52%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.38%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

39

^[4]

3 Years

rr_ExpenseExampleYear03

157

5 Years

rr_ExpenseExampleYear05

286

10 Years

rr_ExpenseExampleYear10

662

GMO CORE PLUS BOND FUND | Return Before Taxes | Class III, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.27%

5 Years

rr_AverageAnnualReturnYear05

2.91%

10 Years

rr_AverageAnnualReturnYear10

5.14%

Incept.

rr_AverageAnnualReturnSinceInception

5.62%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 30, 1997

GMO CORE PLUS BOND FUND | Return Before Taxes | Class IV, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.31%

5 Years

rr_AverageAnnualReturnYear05

2.93%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 26, 2005

GMO CORE PLUS BOND FUND | Return After Taxes on Distributions | Class III, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

10.56%

5 Years

rr_AverageAnnualReturnYear05

(0.60%)

10 Years

rr_AverageAnnualReturnYear10

2.19%

Incept.

rr_AverageAnnualReturnSinceInception

2.75%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 30, 1997

GMO CORE PLUS BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

8.62%

5 Years

rr_AverageAnnualReturnYear05

0.36%

10 Years

rr_AverageAnnualReturnYear10

2.62%

Incept.

rr_AverageAnnualReturnSinceInception

3.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 30, 1997

GMO CORE PLUS BOND FUND | Barclays Capital U.S. Aggregate Index | Class III, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Aggregate Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.54%

5 Years

rr_AverageAnnualReturnYear05

5.80%

10 Years

rr_AverageAnnualReturnYear10

5.84%

Incept.

rr_AverageAnnualReturnSinceInception

6.30%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 30, 1997

GMO CORE PLUS BOND FUND | Barclays Capital U.S. Aggregate Index | Class IV, GMO Core Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Aggregate Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.54%

5 Years

rr_AverageAnnualReturnYear05

5.80%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.46%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 26, 2005

GMO INTERNATIONAL BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 46% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

46.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• foreign bonds and other bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.9 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

•Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

•Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

•Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

•Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

•Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

•Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

•Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

•Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

•Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

•Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

•Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

•Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

•Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

•Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 15.75% (2Q2002)

Lowest Quarter: -12.23% (4Q2008)

Year-to-Date (as of 3/31/11): 1.86%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL BOND FUND | Class III, GMO International Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[46]

Other expenses

rr_OtherExpensesOverAssets

0.21%

^[47]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.07%

^[48]

Total annual operating expenses

rr_ExpensesOverAssets

0.68%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.22%)

^[46]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.46%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

47

^[4]

3 Years

rr_ExpenseExampleYear03

200

5 Years

rr_ExpenseExampleYear05

366

10 Years

rr_ExpenseExampleYear10

848

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(2.61%)

2002

rr_AnnualReturn2002

18.42%

2003

rr_AnnualReturn2003

26.21%

2004

rr_AnnualReturn2004

14.52%

2005

rr_AnnualReturn2005

(8.28%)

2006

rr_AnnualReturn2006

8.11%

2007

rr_AnnualReturn2007

3.37%

2008

rr_AnnualReturn2008

(15.78%)

2009

rr_AnnualReturn2009

19.80%

2010

rr_AnnualReturn2010

14.03%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

15.75%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2002

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(12.23%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.86%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL BOND FUND | Return Before Taxes | Class III, GMO International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

14.03%

5 Years

rr_AverageAnnualReturnYear05

5.16%

10 Years

rr_AverageAnnualReturnYear10

6.99%

Incept.

rr_AverageAnnualReturnSinceInception

7.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 22, 1993

GMO INTERNATIONAL BOND FUND | Return After Taxes on Distributions | Class III, GMO International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

12.10%

5 Years

rr_AverageAnnualReturnYear05

1.22%

10 Years

rr_AverageAnnualReturnYear10

3.43%

Incept.

rr_AverageAnnualReturnSinceInception

3.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 22, 1993

GMO INTERNATIONAL BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

9.09%

5 Years

rr_AverageAnnualReturnYear05

2.04%

10 Years

rr_AverageAnnualReturnYear10

3.86%

Incept.

rr_AverageAnnualReturnSinceInception

4.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 22, 1993

GMO INTERNATIONAL BOND FUND | J.P. Morgan Non-U.S. Government Bond Index | Class III, GMO International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan Non-U.S. Government Bond Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.78%

5 Years

rr_AverageAnnualReturnYear05

8.01%

10 Years

rr_AverageAnnualReturnYear10

7.64%

Incept.

rr_AverageAnnualReturnSinceInception

6.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 22, 1993

GMO STRATEGIC FIXED INCOME FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO STRATEGIC FIXED INCOME FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amounts have been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 19% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

19.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in fixed income securities (see “Name Policies”). The term “fixed income security” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in fixed income securities of any kind (e.g., fixed income securities of any maturity, duration or credit quality). The Fund may invest in any sector of the fixed income market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The Fund may invest all of its assets in below investment grade securities (also known as “junk bonds”). The sectors and types of fixed income securities in which the Fund may invest or hold include, but are not limited to:

• investment grade bonds denominated in various currencies, including bonds issued by the U.S. and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds;

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including below investment grade bonds); and

• asset-backed securities.

The Fund has substantial holdings of Short-Duration Collateral Fund (“SDCF”) (a Fund that primarily holds U.S. asset-backed securities) and World Opportunity Overlay Fund (“Overlay Fund”) (a Fund that invests in asset-backed securities and uses derivatives to attempt to exploit misvaluations in world interest rates, currencies and credit markets).

The Fund may also invest in exchange traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including SDCF and Overlay Fund, and also Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets), High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). For cash management purposes, the Fund may invest in unaffiliated money market funds.

The Fund, primarily though its investments in SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund’s interest rate duration will change depending on the Fund’s investments and the Manager’s assessment of different sectors of the bond market.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 8.76% (2Q2009)

Lowest Quarter: -17.50% (4Q2008)

Year-to-Date (as of 3/31/11): 2.05%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO STRATEGIC FIXED INCOME FUND | Class III, GMO Strategic Fixed Income Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.03%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

^[49]

Total annual operating expenses

rr_ExpensesOverAssets

0.46%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.42%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

43

^[4]

3 Years

rr_ExpenseExampleYear03

150

5 Years

rr_ExpenseExampleYear05

267

10 Years

rr_ExpenseExampleYear10

609

Annual Total Returns

rr_BarChartTableAbstract

2007

rr_AnnualReturn2007

(0.85%)

2008

rr_AnnualReturn2008

(22.21%)

2009

rr_AnnualReturn2009

25.81%

2010

rr_AnnualReturn2010

5.18%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

8.76%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(17.50%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.05%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO STRATEGIC FIXED INCOME FUND | Class VI, GMO Strategic Fixed Income Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.03%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.03%

^[49]

Total annual operating expenses

rr_ExpensesOverAssets

0.37%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.33%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

34

^[4]

3 Years

rr_ExpenseExampleYear03

119

5 Years

rr_ExpenseExampleYear05

213

10 Years

rr_ExpenseExampleYear10

487

GMO STRATEGIC FIXED INCOME FUND | Return Before Taxes | Class III, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.18%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.45%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 13, 2006

GMO STRATEGIC FIXED INCOME FUND | Return Before Taxes | Class VI, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

5.22%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.54%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2006

GMO STRATEGIC FIXED INCOME FUND | Return After Taxes on Distributions | Class III, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

3.96%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(0.10%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 13, 2006

GMO STRATEGIC FIXED INCOME FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.35%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 13, 2006

GMO STRATEGIC FIXED INCOME FUND | J.P. Morgan U.S. 3 Month Cash Index | Class III, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.19%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 13, 2006

GMO STRATEGIC FIXED INCOME FUND | J.P. Morgan U.S. 3 Month Cash Index | Class VI, GMO Strategic Fixed Income Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2006

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan).

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

“Other expenses” have been restated to reflect current fees.

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 51% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

51.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund generally attempts to hedge at least 75% of its net foreign currency exposure into U.S. dollars.

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.6 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 8.23% (3Q2009)

Lowest Quarter: -11.09% (4Q2008)

Year-to-Date (as of 3/31/11): -0.37%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | Class III, GMO Currency Hedged International Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[46]

Other expenses

rr_OtherExpensesOverAssets

0.25%

^[9]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.05%

^[50]

Total annual operating expenses

rr_ExpensesOverAssets

0.70%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.26%)

^[46]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.44%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

45

^[4]

3 Years

rr_ExpenseExampleYear03

202

5 Years

rr_ExpenseExampleYear05

373

10 Years

rr_ExpenseExampleYear10

868

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

6.35%

2002

rr_AnnualReturn2002

3.01%

2003

rr_AnnualReturn2003

8.77%

2004

rr_AnnualReturn2004

8.91%

2005

rr_AnnualReturn2005

7.25%

2006

rr_AnnualReturn2006

2.45%

2007

rr_AnnualReturn2007

(4.00%)

2008

rr_AnnualReturn2008

(13.56%)

2009

rr_AnnualReturn2009

18.81%

2010

rr_AnnualReturn2010

11.70%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

8.23%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(11.09%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

(0.37%)

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | Return Before Taxes | Class III, GMO Currency Hedged International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

11.70%

5 Years

rr_AverageAnnualReturnYear05

2.44%

10 Years

rr_AverageAnnualReturnYear10

4.62%

Incept.

rr_AverageAnnualReturnSinceInception

8.02%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1994

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | Return After Taxes on Distributions | Class III, GMO Currency Hedged International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.94%

5 Years

rr_AverageAnnualReturnYear05

0.93%

10 Years

rr_AverageAnnualReturnYear10

2.37%

Incept.

rr_AverageAnnualReturnSinceInception

4.62%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1994

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Currency Hedged International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

7.61%

5 Years

rr_AverageAnnualReturnYear05

1.19%

10 Years

rr_AverageAnnualReturnYear10

2.57%

Incept.

rr_AverageAnnualReturnSinceInception

4.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1994

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) (Fund benchmark) | Class III, GMO Currency Hedged International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

3.71%

5 Years

rr_AverageAnnualReturnYear05

4.18%

10 Years

rr_AverageAnnualReturnYear10

5.03%

Incept.

rr_AverageAnnualReturnSinceInception

7.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1994

GMO CURRENCY HEDGED INTERNATIONAL BOND FUND | J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) + (Composite index) | Class III, GMO Currency Hedged International Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) + (Composite index)

1 Year

rr_AverageAnnualReturnYear01

3.71%

5 Years

rr_AverageAnnualReturnYear05

4.18%

10 Years

rr_AverageAnnualReturnYear10

4.91%

Incept.

rr_AverageAnnualReturnSinceInception

7.11%

Inception Date

rr_AverageAnnualReturnInceptionDate

Sep. 30, 1994

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

J.P. Morgan Non-U.S. Government Bond Index (Hedged) (ex-Japan) +

GMO GLOBAL BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO GLOBAL BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan Global Government Bond Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 45% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

45.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to the global interest rate, credit and currency markets);

• foreign bonds and other bonds denominated in various currencies, including foreign and U.S. government bonds, asset-backed securities issued by foreign governments and U.S. government agencies (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds, and mortgage-backed and other asset-backed securities issued by private issuers;

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposure to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager normally seeks to maintain the Fund’s estimated interest rate duration within +/- 2 years of the benchmark’s duration (approximately 6.4 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option).

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 13.28% (2Q2002)

Lowest Quarter: -12.70% (4Q2008)

Year-to-Date (as of 3/31/11): 1.67%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO GLOBAL BOND FUND | Class III, GMO Global Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.19%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[46]

Other expenses

rr_OtherExpensesOverAssets

0.12%

^[51]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.04%

^[52]

Total annual operating expenses

rr_ExpensesOverAssets

0.50%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.07%)

^[46]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.43%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

44

^[4]

3 Years

rr_ExpenseExampleYear03

160

5 Years

rr_ExpenseExampleYear05

286

10 Years

rr_ExpenseExampleYear10

655

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(0.62%)

2002

rr_AnnualReturn2002

13.31%

2003

rr_AnnualReturn2003

22.13%

2004

rr_AnnualReturn2004

12.29%

2005

rr_AnnualReturn2005

(5.61%)

2006

rr_AnnualReturn2006

8.53%

2007

rr_AnnualReturn2007

2.76%

2008

rr_AnnualReturn2008

(15.70%)

2009

rr_AnnualReturn2009

20.45%

2010

rr_AnnualReturn2010

14.14%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

13.28%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2002

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(12.70%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year to Date:

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.67%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO GLOBAL BOND FUND | Return Before Taxes | Class III, GMO Global Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

14.14%

5 Years

rr_AverageAnnualReturnYear05

5.27%

10 Years

rr_AverageAnnualReturnYear10

6.54%

Incept.

rr_AverageAnnualReturnSinceInception

6.19%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 1995

GMO GLOBAL BOND FUND | Return After Taxes on Distributions | Class III, GMO Global Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

11.10%

5 Years

rr_AverageAnnualReturnYear05

2.81%

10 Years

rr_AverageAnnualReturnYear10

3.37%

Incept.

rr_AverageAnnualReturnSinceInception

3.40%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 1995

GMO GLOBAL BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Global Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

9.12%

5 Years

rr_AverageAnnualReturnYear05

3.04%

10 Years

rr_AverageAnnualReturnYear10

3.65%

Incept.

rr_AverageAnnualReturnSinceInception

3.58%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 1995

GMO GLOBAL BOND FUND | J.P. Morgan Global Government Bond Index | Class III, GMO Global Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan Global Government Bond Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.42%

5 Years

rr_AverageAnnualReturnYear05

7.35%

10 Years

rr_AverageAnnualReturnYear10

7.12%

Incept.

rr_AverageAnnualReturnSinceInception

5.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 1995

GMO EMERGING COUNTRY DEBT FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO EMERGING COUNTRY DEBT FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan EMBI Global.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 21% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

21.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests primarily in sovereign debt of emerging countries denominated in currencies of developed markets (e.g., U.S. dollar, Euro, Japanese yen, Swiss franc and British pound sterling). Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in debt investments tied economically to emerging countries (see “Name Policies”). The term “emerging countries” means the world’s less developed countries. The Fund typically gains its investment exposure by purchasing debt of sovereign issuers of emerging countries or by using derivatives, typically credit default swaps. The Fund also invests in U.S. and foreign asset-backed securities (including through Short-Duration Collateral Fund (“SDCF”) and World Opportunity Overlay Fund (“Overlay Fund”)). The Fund invests a substantial portion of its assets in below investment grade securities (also known as “junk bonds”). Generally, at least 75% of the Fund’s assets are denominated in, or hedged into, U.S. dollars.

In pursuing its investment objective, the Fund also typically uses exchange-traded and over-the-counter (“OTC”) derivatives, including options, swap contracts (in addition to credit default swaps), currency forwards (including currency forwards on currencies of developed markets), reverse repurchase agreements and futures. The Fund’s performance is likely to be more volatile than that of its benchmark.

The Manager emphasizes a “bottom-up” approach to examining and selecting investments and uses analytical techniques to identify inefficiencies in the pricing of emerging country debt investments and to identify investments the Manager believes are undervalued. The Manager also determines country allocations based on its outlook for a country.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets. The Manager normally seeks to cause the Fund’s estimated interest rate duration to approximate that of its benchmark (approximately 7.1 years as of 05/31/11). For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Fixed Income Funds – Duration.”

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities. Because the Fund typically invests in securities that are of lesser quality than those in its benchmark, in rapidly declining markets, the percentage decline in the value of the Fund is likely to exceed that of its benchmark.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind. Sovereign debt of emerging countries is not widely traded and may be subject to purchase and sale restrictions. In addition, because the Fund typically invests in securities that are less liquid than those in its benchmark, in rapidly declining markets the percentage decline in the Fund’s investments is likely to exceed that of its benchmark.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in a limited number of countries, regions, sectors or companies creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 20.29% (3Q2009)

Lowest Quarter: -23.39% (4Q2008)

Year-to-Date (as of 3/31/11): 2.53%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO EMERGING COUNTRY DEBT FUND | Class III, GMO Emerging Country Debt Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.35%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[53]

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[54]

Total annual operating expenses

rr_ExpensesOverAssets

0.65%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

168

^[4]

3 Years

rr_ExpenseExampleYear03

314

5 Years

rr_ExpenseExampleYear05

472

10 Years

rr_ExpenseExampleYear10

933

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

116

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

257

5 Years

rr_ExpenseExampleNoRedemptionYear05

410

10 Years

rr_ExpenseExampleNoRedemptionYear10

856

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

14.19%

2002

rr_AnnualReturn2002

19.35%

2003

rr_AnnualReturn2003

36.39%

2004

rr_AnnualReturn2004

19.00%

2005

rr_AnnualReturn2005

15.77%

2006

rr_AnnualReturn2006

14.81%

2007

rr_AnnualReturn2007

9.19%

2008

rr_AnnualReturn2008

(33.25%)

2009

rr_AnnualReturn2009

50.17%

2010

rr_AnnualReturn2010

25.64%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

20.29%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(23.39%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.53%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO EMERGING COUNTRY DEBT FUND | Class IV, GMO Emerging Country Debt Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.50%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.50%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.35%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

^[53]

Other expenses

rr_OtherExpensesOverAssets

0.15%

^[54]

Total annual operating expenses

rr_ExpensesOverAssets

0.60%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

163

^[4]

3 Years

rr_ExpenseExampleYear03

298

5 Years

rr_ExpenseExampleYear05

445

10 Years

rr_ExpenseExampleYear10

873

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

111

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

241

5 Years

rr_ExpenseExampleNoRedemptionYear05

383

10 Years

rr_ExpenseExampleNoRedemptionYear10

796

GMO EMERGING COUNTRY DEBT FUND | Return Before Taxes | Class III, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

24.39%

5 Years

rr_AverageAnnualReturnYear05

9.34%

10 Years

rr_AverageAnnualReturnYear10

14.88%

Incept.

rr_AverageAnnualReturnSinceInception

17.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 19, 1994

GMO EMERGING COUNTRY DEBT FUND | Return Before Taxes | Class IV, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

24.50%

5 Years

rr_AverageAnnualReturnYear05

9.40%

10 Years

rr_AverageAnnualReturnYear10

14.95%

Incept.

rr_AverageAnnualReturnSinceInception

12.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO EMERGING COUNTRY DEBT FUND | Return After Taxes on Distributions | Class III, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

19.02%

5 Years

rr_AverageAnnualReturnYear05

5.30%

10 Years

rr_AverageAnnualReturnYear10

10.08%

Incept.

rr_AverageAnnualReturnSinceInception

10.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 19, 1994

GMO EMERGING COUNTRY DEBT FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

15.35%

5 Years

rr_AverageAnnualReturnYear05

5.64%

10 Years

rr_AverageAnnualReturnYear10

10.06%

Incept.

rr_AverageAnnualReturnSinceInception

10.94%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 19, 1994

GMO EMERGING COUNTRY DEBT FUND | J.P. Morgan EMBI Global (Fund benchmark) | Class III, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan EMBI Global (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

12.04%

5 Years

rr_AverageAnnualReturnYear05

8.36%

10 Years

rr_AverageAnnualReturnYear10

10.29%

Incept.

rr_AverageAnnualReturnSinceInception

12.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 19, 1994

GMO EMERGING COUNTRY DEBT FUND | J.P. Morgan EMBI Global (Fund benchmark) | Class IV, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

J.P. Morgan EMBI Global (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

12.04%

5 Years

rr_AverageAnnualReturnYear05

8.36%

10 Years

rr_AverageAnnualReturnYear10

10.29%

Incept.

rr_AverageAnnualReturnSinceInception

9.94%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

GMO EMERGING COUNTRY DEBT FUND | J.P. Morgan EMBI Global+ (Composite index) | Class III, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan EMBI Global+ (Composite index)

1 Year

rr_AverageAnnualReturnYear01

12.04%

5 Years

rr_AverageAnnualReturnYear05

8.36%

10 Years

rr_AverageAnnualReturnYear10

10.29%

Incept.

rr_AverageAnnualReturnSinceInception

11.98%

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 19, 1994

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

J.P. Morgan EMBI Global+

GMO EMERGING COUNTRY DEBT FUND | J.P. Morgan EMBI Global+ (Composite index) | Class IV, GMO Emerging Country Debt Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

J.P. Morgan EMBI Global+ (Composite index)

1 Year

rr_AverageAnnualReturnYear01

12.04%

5 Years

rr_AverageAnnualReturnYear05

8.36%

10 Years

rr_AverageAnnualReturnYear10

10.29%

Incept.

rr_AverageAnnualReturnSinceInception

9.83%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jan. 09, 1998

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

J.P. Morgan EMBI Global+

GMO SHORT-DURATION INVESTMENT FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO SHORT-DURATION INVESTMENT FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Provide current income.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

Historically, the Fund has sought to provide current income to the extent consistent with the preservation of capital and liquidity. The Fund primarily holds shares of Short Duration Collateral Fund (“SDCF”). SDCF primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, SDCF has invested in government securities, corporate debt securities, money market instruments and commercial paper and has entered into credit default swaps, reverse repurchase agreements, and repurchase agreements. SDCF has also used other exchange-traded and over-the-counter (“OTC”) derivatives. The Fund also has invested directly in asset-backed securities issued by private issuers, U.S. government and agency securities (including securities neither guaranteed nor insured by the U.S. government), corporate debt securities, money market instruments, prime commercial paper and master demand notes, and certificates of deposit, bankers’ acceptances and other bank obligations.

Because of the deterioration in credit markets that became acute in 2008, the Fund, in particular through its investment in SDCF, currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

The Fund is not a money market fund and is not subject to the duration, quality, diversification and other requirements applicable to money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 6.11% (2Q2009)

Lowest Quarter: -10.36% (4Q2008)

Year-to-Date (as of 3/31/11): 0.72%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO SHORT-DURATION INVESTMENT FUND | Class III, GMO Short-Duration Investment Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.05%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.94%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

^[55]

Total annual operating expenses

rr_ExpensesOverAssets

1.16%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.94%)

^[56]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.22%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

23

^[4]

3 Years

rr_ExpenseExampleYear03

290

5 Years

rr_ExpenseExampleYear05

578

10 Years

rr_ExpenseExampleYear10

1,399

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

4.99%

2002

rr_AnnualReturn2002

(4.62%)

2003

rr_AnnualReturn2003

1.65%

2004

rr_AnnualReturn2004

2.85%

2005

rr_AnnualReturn2005

3.36%

2006

rr_AnnualReturn2006

6.39%

2007

rr_AnnualReturn2007

2.74%

2008

rr_AnnualReturn2008

(14.01%)

2009

rr_AnnualReturn2009

14.28%

2010

rr_AnnualReturn2010

4.90%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

6.11%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(10.36%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

0.72%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO SHORT-DURATION INVESTMENT FUND | Return Before Taxes | Class III, GMO Short-Duration Investment Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.90%

5 Years

rr_AverageAnnualReturnYear05

2.42%

10 Years

rr_AverageAnnualReturnYear10

2.00%

Incept.

rr_AverageAnnualReturnSinceInception

4.10%

^[57]

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 18, 1990

GMO SHORT-DURATION INVESTMENT FUND | Return After Taxes on Distributions | Class III, GMO Short-Duration Investment Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

4.68%

5 Years

rr_AverageAnnualReturnYear05

1.20%

10 Years

rr_AverageAnnualReturnYear10

0.76%

Incept.

rr_AverageAnnualReturnSinceInception

2.30%

^[57]

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 18, 1990

GMO SHORT-DURATION INVESTMENT FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Short-Duration Investment Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.18%

5 Years

rr_AverageAnnualReturnYear05

1.35%

10 Years

rr_AverageAnnualReturnYear10

0.98%

Incept.

rr_AverageAnnualReturnSinceInception

2.42%

^[57]

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 18, 1990

GMO SHORT-DURATION INVESTMENT FUND | J.P. Morgan U.S. 3 Month Cash Index | Class III, GMO Short-Duration Investment Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

3.37%

10 Years

rr_AverageAnnualReturnYear10

2.99%

Incept.

rr_AverageAnnualReturnSinceInception

4.43%

^[57]

Inception Date

rr_AverageAnnualReturnInceptionDate

Apr. 18, 1990

GMO SHORT-DURATION COLLATERAL FUND

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.03%

^[9]

Total annual operating expenses

rr_ExpensesOverAssets

0.03%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[58]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.01%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

GMO Short-Duration Collateral Fund

1 Year

rr_ExpenseExampleYear01

1

^[4]

3 Years

rr_ExpenseExampleYear03

8

5 Years

rr_ExpenseExampleYear05

15

10 Years

rr_ExpenseExampleYear10

37

Annual Total Returns

rr_BarChartTableAbstract

2003

rr_AnnualReturn2003

2.32%

2004

rr_AnnualReturn2004

1.98%

2005

rr_AnnualReturn2005

3.57%

2006

rr_AnnualReturn2006

5.56%

2007

rr_AnnualReturn2007

1.83%

2008

rr_AnnualReturn2008

(19.27%)

2009

rr_AnnualReturn2009

25.20%

2010

rr_AnnualReturn2010

10.14%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.78%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(15.22%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.56%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO SHORT-DURATION COLLATERAL FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO SHORT-DURATION COLLATERAL FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return comparable to that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

0.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

The Fund primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, the Fund has invested in government securities, corporate debt securities, money market instruments and commercial paper and has entered into credit default swaps, reverse repurchase agreements and repurchase agreements. The Fund has also used other exchange-traded and over-the-counter (“OTC”) derivatives.

Because of the deterioration in credit markets that became acute in 2008, the Fund currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for the Fund.

Since October 2008, the Fund has declared and paid distributions when it has acquired a meaningful cash position rather than reinvesting that cash in portfolio securities. The Fund currently intends to continue this practice. A substantial portion of any such distributions could constitute a return of capital to shareholders for tax purposes. See “Distributions and Taxes” below for more information on the tax implications of such distributions.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 9.78% (2Q2009)

Lowest Quarter: -15.22% (4Q2008)

Year-to-Date (as of 3/31/11): 1.56%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO SHORT-DURATION COLLATERAL FUND | Return Before Taxes

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

10.14%

5 Years

rr_AverageAnnualReturnYear05

3.65%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 2002

GMO SHORT-DURATION COLLATERAL FUND | Return After Taxes on Distributions

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

^[39]

1 Year

rr_AverageAnnualReturnYear01

9.61%

5 Years

rr_AverageAnnualReturnYear05

2.31%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.12%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 2002

GMO SHORT-DURATION COLLATERAL FUND | Return After Taxes on Distributions and Sale of Fund Shares

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

^[39]

1 Year

rr_AverageAnnualReturnYear01

6.57%

5 Years

rr_AverageAnnualReturnYear05

2.31%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.06%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 2002

GMO SHORT-DURATION COLLATERAL FUND | J.P. Morgan U.S. 3 Month Cash Index

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

3.37%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.86%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 2002

GMO SHORT-DURATION COLLATERAL SHARE FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO SHORT-DURATION COLLATERAL SHARE FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return comparable to that of its benchmark, the J.P. Morgan U.S. 3 Month Cash Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 5% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

5.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund invests substantially all of its assets in Short-Duration Collateral Fund (“SDCF”) (see page 100 for a discussion of SDCF). The Fund also may invest in U.S. Treasury Fund, unaffiliated money market funds, cash and cash equivalents. Its investment objective and principal investment strategies, therefore, are substantially similar to those of SDCF. SDCF is not currently pursuing its investment objective or an active investment program and is not acquiring new investments.

SDCF primarily holds asset-backed securities, including, but not limited to, securities backed by pools of residential and commercial mortgages, credit-card receivables, home equity loans, automobile loans, educational loans, corporate and sovereign bonds and bank loans made to corporations. In addition, SDCF has invested in government securities, corporate debt securities, money market instruments, and commercial paper, and has entered into credit default swaps, reverse repurchase agreements and repurchase agreements. SDCF has also used exchange-traded and over-the-counter (“OTC”) derivatives. Because of the deterioration in credit markets that became acute in 2008, the Fund, through its holdings of SDCF, currently has and is expected to continue to have material exposure to below investment grade securities.

The Manager does not seek to maintain a specified interest rate duration for SDCF.

Since October of 2008, SDCF has declared and paid distributions when it has acquired a meaningful cash position rather than reinvesting that cash in portfolio securities. SDCF currently intends to continue this practice. A substantial portion of any such distributions could constitute a return of capital to SDCF shareholders, including the Fund, for tax purposes. Therefore, if the Fund, in turn, distributes these amounts to its shareholders, the Fund’s distributions similarly could constitute a return of capital to Fund shareholders for tax purposes. See “Distributions and Taxes” below for more information on the tax implications of such distributions.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. Because the Fund invests substantially all of its assets in SDCF, the most significant risks of investing in the Fund are the risks to which the Fund is exposed through SDCF, which include those outlined in the following brief summary of principal risks. For a more complete discussion of these risks, see “Description of Principal Risks.” The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified.

• Market Risk – Fixed Income Securities – Typically, the market value of SDCF’s fixed income securities will decline during periods of widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent SDCF from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund and SDCF are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or SDCF may affect the Fund’s performance more than if the Fund or SDCF were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 9.62% (2Q2009)

Lowest Quarter: -14.97% (4Q2008)

Year-to-Date (as of 3/31/11): 1.52%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO SHORT-DURATION COLLATERAL SHARE FUND | Class III, GMO Short-Duration Collateral Share Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.05%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

Other expenses

rr_OtherExpensesOverAssets

0.16%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[59]

Total annual operating expenses

rr_ExpensesOverAssets

0.37%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.16%)

^[60]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.21%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

22

^[4]

3 Years

rr_ExpenseExampleYear03

107

5 Years

rr_ExpenseExampleYear05

201

10 Years

rr_ExpenseExampleYear10

475

Annual Total Returns

rr_BarChartTableAbstract

2007

rr_AnnualReturn2007

1.63%

2008

rr_AnnualReturn2008

(19.16%)

2009

rr_AnnualReturn2009

24.68%

2010

rr_AnnualReturn2010

9.92%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.62%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(14.97%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.52%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO SHORT-DURATION COLLATERAL SHARE FUND | Class VI, GMO Short-Duration Collateral Share Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.05%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

Other expenses

rr_OtherExpensesOverAssets

0.16%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.01%

^[59]

Total annual operating expenses

rr_ExpensesOverAssets

0.28%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.16%)

^[60]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.12%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

12

^[4]

3 Years

rr_ExpenseExampleYear03

78

5 Years

rr_ExpenseExampleYear05

150

10 Years

rr_ExpenseExampleYear10

363

GMO SHORT-DURATION COLLATERAL SHARE FUND | Return Before Taxes | Class III, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.92%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2006

GMO SHORT-DURATION COLLATERAL SHARE FUND | Return Before Taxes | Class VI, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

^[61]

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.92%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.43%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 01, 2006

GMO SHORT-DURATION COLLATERAL SHARE FUND | Return After Taxes on Distributions | Class III, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.54%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.78%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2006

GMO SHORT-DURATION COLLATERAL SHARE FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.81%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2006

GMO SHORT-DURATION COLLATERAL SHARE FUND | J.P. Morgan U.S. 3 Month Cash Index | Class III, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.90%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 28, 2006

GMO SHORT-DURATION COLLATERAL SHARE FUND | J.P. Morgan U.S. 3 Month Cash Index | Class VI, GMO Short-Duration Collateral Share Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

^[61]

Label

rr_AverageAnnualReturnLabel

J.P. Morgan U.S. 3 Month Cash Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.33%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 01, 2006

GMO INFLATION INDEXED PLUS BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INFLATION INDEXED PLUS BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the Barclays Capital U.S. Treasury Inflation Notes Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

"Other expenses" have been restated to reflect current fees.

The amounts have been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 81% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

81.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund’s investment program has two principal components. One component seeks to replicate the Fund’s benchmark. The second component seeks to add value relative to the Fund’s benchmark by taking positions that may be unrelated to its benchmark in global interest rate, currency and credit markets (particularly in asset-backed and emerging country debt markets). These positions can cause the Fund’s performance to differ significantly from that of its benchmark.

In deciding on what positions to take in global interest rate and currency markets, and for the size of those positions, the Manager considers fundamental factors (e.g., inflation and current account positions) as well as price-based factors (e.g., interest and exchange rates). The Manager assesses the relative values across global interest rate and currency markets, and considers the merits of overweighting or underweighting positions in currencies and interest rates. The Manager also may consider the relative attractiveness of yield curve and duration positions in these markets.

In selecting credit investments, the Manager uses fundamental investment techniques to assess the expected performance of these investments relative to the Fund’s benchmark.

In implementing these strategies, the Fund may hold or invest in:

• derivatives, including without limitation, futures contracts, currency options, interest rate options, currency forwards, reverse repurchase agreements, credit default swaps and other swap contracts (to generate a return comparable to the Fund’s benchmark and to gain exposure to inflation indexed bonds and/or the global interest rate, credit and currency markets);

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• non-inflation indexed (or nominal) fixed income securities issued by the U.S. and foreign governments and their agencies or instrumentalities (including securities neither guaranteed nor insured by the U.S. government) and by corporations (to gain direct exposure to such securities and/or for use as part of a synthetic position);

• shares of Short-Duration Collateral Fund (“SDCF”) (to have exposure to asset-backed securities);

• shares of World Opportunity Overlay Fund (“Overlay Fund”) (to gain exposure to the global interest rate, credit and currency markets);

• shares of Emerging Country Debt Fund (“ECDF”) (to gain exposure to emerging country debt markets);

• shares of U.S. Treasury Fund and unaffiliated money market funds (for cash management purposes);

• shares of High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments); and

• shares of Debt Opportunities Fund (to gain exposure to global credit markets).

The Fund, primarily through its investments in shares of SDCF, Overlay Fund and ECDF, has and is expected to continue to have material exposures to below investment grade U.S. asset-backed and emerging country debt securities. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in inflation indexed bonds (see “Name Policies”). For purposes of this Prospectus, the term “inflation indexed bonds” includes instruments that are “linked” to general measures of inflation because their principal and/or interest components change with general movements of inflation in the country of issue.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads. In addition, increases in real interest rates may not be accompanied by increases in nominal interest rates. In such instances, the value of inflation indexed bonds may experience greater declines than non-inflation indexed (or nominal) fixed income investments with similar maturities. There can be no assurance that the value of the Fund’s inflation indexed bond investments will change in the same proportion as changes in nominal interest rates, and short-term increases in inflation may lead to a decline in their value.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. The Fund’s investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may or may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund’s use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another, such as the Fund’s investments in asset-backed securities secured by different types of consumer debt (e.g., credit-card receivables, automobile loans and home equity loans), creates additional risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund’s foreign currency holdings and investments denominated in foreign currencies.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 9.31% (3Q2009)

Lowest Quarter: -21.90% (4Q2008)

Year-to-Date (as of 3/31/11): 2.92%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INFLATION INDEXED PLUS BOND FUND | Class III, GMO Inflation Indexed Plus Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[62]

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[63]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.08%

^[64]

Total annual operating expenses

rr_ExpensesOverAssets

0.67%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.20%)

^[62]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.47%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

48

^[4]

3 Years

rr_ExpenseExampleYear03

199

5 Years

rr_ExpenseExampleYear05

362

10 Years

rr_ExpenseExampleYear10

838

Annual Total Returns

rr_BarChartTableAbstract

2007

rr_AnnualReturn2007

2.91%

2008

rr_AnnualReturn2008

(24.77%)

2009

rr_AnnualReturn2009

30.25%

2010

rr_AnnualReturn2010

13.93%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.31%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(21.90%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.92%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INFLATION INDEXED PLUS BOND FUND | Class VI, GMO Inflation Indexed Plus Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

^[62]

Other expenses

rr_OtherExpensesOverAssets

0.19%

^[63]

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.08%

^[64]

Total annual operating expenses

rr_ExpensesOverAssets

0.58%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.20%)

^[62]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.38%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

39

^[4]

3 Years

rr_ExpenseExampleYear03

168

5 Years

rr_ExpenseExampleYear05

308

10 Years

rr_ExpenseExampleYear10

718

GMO INFLATION INDEXED PLUS BOND FUND | Return Before Taxes | Class III, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

13.93%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.96%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 29, 2006

GMO INFLATION INDEXED PLUS BOND FUND | Return Before Taxes | Class VI, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

14.15%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.98%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2006

GMO INFLATION INDEXED PLUS BOND FUND | Return After Taxes on Distributions | Class III, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

11.45%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.70%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 29, 2006

GMO INFLATION INDEXED PLUS BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

9.20%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.41%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 29, 2006

GMO INFLATION INDEXED PLUS BOND FUND | Barclays Capital U.S. Treasury Inflation Notes Index | Class III, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Treasury Inflation Notes Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.31%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.46%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 29, 2006

GMO INFLATION INDEXED PLUS BOND FUND | Barclays Capital U.S. Treasury Inflation Notes Index | Class VI, GMO Inflation Indexed Plus Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Treasury Inflation Notes Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.31%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2006

GMO U.S. TREASURY FUND

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Management fee

rr_ManagementFeesOverAssets

0.08%

^[65]

Other expenses

rr_OtherExpensesOverAssets

0.03%

Total annual operating expenses

rr_ExpensesOverAssets

0.11%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.03%)

^[65]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.08%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

GMO U.S. Treasury Fund

1 Year

rr_ExpenseExampleYear01

8

^[4]

3 Years

rr_ExpenseExampleYear03

32

5 Years

rr_ExpenseExampleYear05

59

10 Years

rr_ExpenseExampleYear10

138

Annual Total Returns

rr_BarChartTableAbstract

2010

rr_AnnualReturn2010

0.10%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

0.07%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(0.02%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Mar. 31, 2010

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

0.03%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. TREASURY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. TREASURY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Liquidity and safety of principal with

Objective, Secondary [Text Block]

rr_ObjectiveSecondaryTextBlock

current income as a secondary objective.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 0% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

0.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in Direct U.S. Treasury Obligations and repurchase agreements collateralized by these Obligations (see “Name Policies”). “Direct U.S. Treasury Obligations” include U.S. Treasury bills, bonds and notes and other securities issued by the U.S. Treasury, as well as Separately Traded Registered Interest and Principal Securities (STRIPS) and other zero-coupon securities. The Manager normally seeks to maintain an interest rate duration of one year or less for the Fund’s portfolio. For an additional discussion of duration, see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses — Fixed Income Funds — Duration.”

The Fund may also enter into repurchase agreements, under which the Fund purchases a security backed by the full faith and credit of the U.S. government from a seller who simultaneously commits to repurchase, on an agreed upon date in the future, the security from the Fund at the original purchase price plus an agreed upon amount representing the original purchase price plus interest. The counterparties in repurchase agreements are typically broker-dealers and banks, and the safety of the arrangement is dependent on, among other things, the Fund having an interest in the security that can be realized in the event of the insolvency of the counterparty.

In addition to Direct U.S. Treasury Obligations, the Fund may invest in other fixed-income securities that are backed by the full faith and credit of the U.S. government, such as guaranteed securities issued by the Government National Mortgage Association (GNMA) and the Federal Deposit Insurance Corporation (FDIC). For cash management purposes, the Fund may invest in unaffiliated money market funds.

Although the fixed-income securities purchased by the Fund normally will have a stated or remaining maturity of one year or less, Direct U.S. Treasury Obligations purchased pursuant to repurchase agreements may not, and, therefore, if the counterparty to the repurchase agreement defaults, the Fund may end up owning a security with a stated or remaining maturity of more than one year.

The Fund is not a money market fund and is not subject to the duration, quality, diversification and other requirements applicable to money market funds.

In selecting U.S. Treasury securities for the Fund’s portfolio, the Manager focuses primarily on the relative attractiveness of different obligations (such as bonds, notes or bills), which can vary depending on the general level of interest rates as well as supply/demand imbalances and other market conditions.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund’s U.S. Treasury and other fixed income securities will decline during periods of rising interest rates, and yields on the Fund’s securities may equal or approach zero under some market conditions.

• Credit Risk – Securities issued by the U.S. Treasury or U.S. government agencies generally present minimal credit risk. However, a security backed by the full faith and credit of the U.S. government is guaranteed only as to the timely payment of interest and principal when held to maturity. The market prices for such securities are not guaranteed and will fluctuate.

• Focused Investment Risk – Focusing investments in a particular type of security (e.g., Direct U.S. Treasury Obligations) creates additional risk.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns Year Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 0.07% (2Q2010)

Lowest Quarter: -0.02% (1Q2010)

Year-to-Date (as of 3/31/11): 0.03%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO U.S. TREASURY FUND | Return Before Taxes

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

0.10%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.21%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 17, 2009

GMO U.S. TREASURY FUND | Return After Taxes on Distributions

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

0.05%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 17, 2009

GMO U.S. TREASURY FUND | Return After Taxes on Distributions and Sale of Fund Shares

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

0.06%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 17, 2009

GMO U.S. TREASURY FUND | Citigroup 3-Month Treasury Bill Index

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Label

rr_AverageAnnualReturnLabel

Citigroup 3-Month Treasury Bill Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 17, 2009

GMO ASSET ALLOCATION BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO ASSET ALLOCATION BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the Citigroup 3-Month Treasury Bill Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 315% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

315.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager pursues the Fund’s investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund’s strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in bonds of any kind (e.g., bonds of any maturity, duration or credit quality).

The Fund may invest in any sector of the bond market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The sectors and types of bonds in which the Fund may invest include, but are not limited to:

• investment grade bonds denominated in various currencies, including bonds issued by the U.S. and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds (also known as “junk bonds”);

• inflation indexed bonds issued by the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and foreign governments and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including junk bonds); and

• asset-backed securities, including mortgage related and mortgage-backed securities.

The Fund may also invest in exchange traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). The Fund also may invest in unaffiliated money market funds for cash management purposes.

The Fund may invest up to 100% of its assets in junk bonds.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund’s interest rate duration will change depending on the Fund’s investments and the Manager’s assessment of different sectors of the bond market.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund's fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. The Fund's investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Leveraging Risk – The Fund's use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing the Fund’s annual total return for the period indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Year Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 1.83% (3Q2010)

Lowest Quarter: -0.36% (4Q2010)

Year-to-Date (as of 3/31/11): 1.94%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO ASSET ALLOCATION BOND FUND | Class III, GMO Asset Allocation Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.08%

^[66]

Total annual operating expenses

rr_ExpensesOverAssets

0.48%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.44%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

45

^[4]

3 Years

rr_ExpenseExampleYear03

148

5 Years

rr_ExpenseExampleYear05

260

10 Years

rr_ExpenseExampleYear10

589

Annual Total Returns

rr_BarChartTableAbstract

2010

rr_AnnualReturn2010

4.02%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

1.83%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(0.36%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2010

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.94%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO ASSET ALLOCATION BOND FUND | Class VI, GMO Asset Allocation Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.08%

^[66]

Total annual operating expenses

rr_ExpensesOverAssets

0.39%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.04%)

^[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.35%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

36

^[4]

3 Years

rr_ExpenseExampleYear03

119

5 Years

rr_ExpenseExampleYear05

210

10 Years

rr_ExpenseExampleYear10

477

GMO ASSET ALLOCATION BOND FUND | Return Before Taxes | Class III, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.02%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.85%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 27, 2009

GMO ASSET ALLOCATION BOND FUND | Return Before Taxes | Class VI, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.14%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.24%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 18, 2009

GMO ASSET ALLOCATION BOND FUND | Return After Taxes on Distributions | Class III, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

0.95%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.49%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 27, 2009

GMO ASSET ALLOCATION BOND FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distribution and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

2.63%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.66%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 27, 2009

GMO ASSET ALLOCATION BOND FUND | Citigroup 3-Month Treasury Bill Index | Class III, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Citigroup 3-Month Treasury Bill Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 27, 2009

GMO ASSET ALLOCATION BOND FUND | Citigroup 3-Month Treasury Bill Index | Class VI, GMO Asset Allocation Bond Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class VI

Label

rr_AverageAnnualReturnLabel

Citigroup 3-Month Treasury Bill Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 18, 2009

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return in excess of that of its benchmark, the J.P. Morgan Non-U.S. Government Bond Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The table below describes the fees and expenses that you may pay for each class of shares if you buy and hold shares of the Fund.

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Other Expenses, New Fund, Based on Estimates [Text]

rr_OtherExpensesNewFundBasedOnEstimates

The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated, regardless of whether or not you redeem your shares at the end of such periods. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. Because the Fund commenced operations on or following the date of this Prospectus, the Fund’s portfolio turnover rate is not available.

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Manager pursues the Fund's investment objective by using investment strategies designed to complement broader asset allocation strategies being implemented by the Manager in other Asset Allocation Funds or accounts. Accordingly, the Fund is not a standalone investment. The Manager uses multi-year forecasts of relative value and risk to determine the Fund's strategic direction.

Under normal circumstances, the Fund invests directly and indirectly (e.g., through other GMO Funds or derivatives) at least 80% of its assets in bonds (see “Name Policies”). The term “bond” includes (i) obligations of an issuer to make payments of principal and/or interest (whether fixed or variable) on future dates and (ii) synthetic debt instruments created by the Manager by using derivatives (e.g., a futures contract, swap contract, currency forward or option). The Fund is permitted to invest in bonds of any kind (e.g., bonds of any maturity, duration or credit quality). While the Fund principally invests in non-U.S. bonds, it may invest in any sector of the bond market and is not required to maintain a minimum or maximum allocation of investments in any one sector. The sectors and types of bonds in which the Fund may invest include, but are not limited to:

• foreign government securities and other investment grade bonds denominated in various currencies, including bonds issued by the U.S. government, and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. government), corporate bonds and taxable and tax-exempt municipal bonds;

• below investment grade bonds (also known as “junk bonds”);

• inflation indexed bonds issued by foreign governments and the U.S. government (including Inflation-Protected Securities issued by the U.S. Treasury (TIPS)) and their agencies or instrumentalities (as well as bonds neither guaranteed nor insured by the U.S. and/or foreign governments) and inflation indexed bonds issued by corporations;

• sovereign debt of emerging countries and other bonds issued in emerging countries (including junk bonds); and

• asset-backed securities, including mortgage related and mortgage-backed securities.

The Fund may also invest in exchange-traded and over-the-counter (“OTC”) derivatives, including futures contracts, currency options, currency forwards, reverse repurchase agreements, swap contracts (including credit default swaps), interest rate options, swaps on interest rates and other types of derivatives. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Fund may gain exposure to the investments described above through investments in shares of other GMO Funds, including High Quality Short-Duration Bond Fund (to seek to generate a return in excess of that of the J.P. Morgan U.S. 3 Month Cash Index by investing in a wide variety of high quality U.S. and foreign debt investments), Debt Opportunities Fund (to gain exposure to global credit markets) and U.S. Treasury Fund (for cash management purposes). The Fund also may invest in unaffiliated money market funds for cash management purposes.

The Fund may invest up to 100% of its assets in junk bonds.

The Manager does not seek to maintain a specified interest rate duration for the Fund, and the Fund's interest rate duration will change depending on the Fund's investments and the Manager's assessment of different sectors of the bond market.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund's performance more than if the Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, see “Description of Principal Risks.”

• Currency Risk – Fluctuations in exchange rates will adversely affect the market value of the Fund's foreign currency holdings and investments denominated in foreign currencies.

• Market Risk – Fixed Income Securities – Typically, the market value of the Fund's fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. The Fund's investments in below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations. The risk of counterparty default is particularly acute in economic environments in which financial services firms are exposed to systemic risks of the type evidenced by the insolvency of Lehman Brothers in 2008 and subsequent market disruptions.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Leveraging Risk – The Fund's use of reverse repurchase agreements and other derivatives and securities lending may cause its portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions or sectors or in industries with high positive correlations to one another creates additional risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in underlying funds, including the risk that the underlying funds in which it invests will not perform as expected.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund is a non-diversified investment company under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund may affect the Fund’s performance more than if the Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

Performance One Year or Less [Text]

rr_PerformanceOneYearOrLess

Because the Fund had not yet completed a full calendar year of operations as of the date of this Prospectus, performance information for the Fund is not included.

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND | Class III, GMO Asset Allocation International Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.18%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.58%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

^[17],[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.40%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

59

3 Years

rr_ExpenseExampleYear03

186

GMO ASSET ALLOCATION INTERNATIONAL BOND FUND | Class VI, GMO Asset Allocation International Bond Fund

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class VI

Management fee

rr_ManagementFeesOverAssets

0.25%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.055%

^[44]

Other expenses

rr_OtherExpensesOverAssets

0.18%

^[17]

Total annual operating expenses

rr_ExpensesOverAssets

0.49%

^[17]

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.18%)

^[17],[44]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.31%

^[17]

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class VI

1 Year

rr_ExpenseExampleYear01

50

3 Years

rr_ExpenseExampleYear03

157

GMO U.S. EQUITY ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO U.S. EQUITY ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the Russell 3000 Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 7% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

7.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of the U.S. Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of Flexible Equities Fund (together with the U.S. Equity Funds, the “underlying Funds”). In addition, the Fund may hold securities directly. The Fund primarily seeks exposure to U.S. equity investments (which may include both growth and value style equities and equities of any market capitalization). The Fund also may have exposure to foreign equity investments. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments tied economically to the U.S. (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among major sectors in the U.S. equity market (large-cap value, large-cap growth, large-cap core, small- and mid-cap value, small- and mid-cap growth and real estate/REIT) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund's or the underlying Fund's performance more than if the Fund or the underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Leveraging Risk – The use of derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund’s or the underlying Fund’s performance more than if the Fund or the underlying Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

^[67]

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 18.06% (2Q2003)

Lowest Quarter: -16.54% (3Q2002)

Year to Date (as of 3/31/11): 4.15%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

^[67]

GMO U.S. EQUITY ALLOCATION FUND | Class III, GMO U.S. Equity Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.06%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.39%

^[68]

Total annual operating expenses

rr_ExpensesOverAssets

0.45%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.06%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.39%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

40

^[4]

3 Years

rr_ExpenseExampleYear03

151

5 Years

rr_ExpenseExampleYear05

273

10 Years

rr_ExpenseExampleYear10

629

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

40

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

151

5 Years

rr_ExpenseExampleNoRedemptionYear05

273

10 Years

rr_ExpenseExampleNoRedemptionYear10

629

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

7.27%

2002

rr_AnnualReturn2002

(13.24%)

2003

rr_AnnualReturn2003

31.78%

2004

rr_AnnualReturn2004

11.55%

2005

rr_AnnualReturn2005

3.21%

2006

rr_AnnualReturn2006

10.35%

2007

rr_AnnualReturn2007

2.22%

2008

rr_AnnualReturn2008

(27.34%)

2009

rr_AnnualReturn2009

20.51%

2010

rr_AnnualReturn2010

7.70%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.06%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(16.54%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2002

Year To Date Return, Label

rr_YearToDateReturnLabel

Year to Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

4.15%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO U.S. EQUITY ALLOCATION FUND | Return Before Taxes | Class III, GMO U.S. Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.70%

5 Years

rr_AverageAnnualReturnYear05

1.24%

10 Years

rr_AverageAnnualReturnYear10

4.15%

Incept.

rr_AverageAnnualReturnSinceInception

9.97%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1992

GMO U.S. EQUITY ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO U.S. Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

7.38%

5 Years

rr_AverageAnnualReturnYear05

0.17%

10 Years

rr_AverageAnnualReturnYear10

3.24%

Incept.

rr_AverageAnnualReturnSinceInception

6.15%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1992

GMO U.S. EQUITY ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO U.S. Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.38%

5 Years

rr_AverageAnnualReturnYear05

1.90%

10 Years

rr_AverageAnnualReturnYear10

3.59%

Incept.

rr_AverageAnnualReturnSinceInception

7.07%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1992

GMO U.S. EQUITY ALLOCATION FUND | Russell 3000 Index (Fund benchmark) | Class III, GMO U.S. Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 3000 Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

16.93%

5 Years

rr_AverageAnnualReturnYear05

2.74%

10 Years

rr_AverageAnnualReturnYear10

2.16%

Incept.

rr_AverageAnnualReturnSinceInception

8.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1992

GMO U.S. EQUITY ALLOCATION FUND | Russell 3000 ++ Index (Composite index) | Class III, GMO U.S. Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Russell 3000 ++ Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

16.93%

5 Years

rr_AverageAnnualReturnYear05

2.74%

10 Years

rr_AverageAnnualReturnYear10

2.03%

Incept.

rr_AverageAnnualReturnSinceInception

8.51%

Inception Date

rr_AverageAnnualReturnInceptionDate

Dec. 31, 1992

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Russell 3000 ++ Index

GMO INTERNATIONAL EQUITY ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL EQUITY ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the MSCI ACWI ex-U.S. Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 13% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

13.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), as well as to the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 21.94% (2Q2009)

Lowest Quarter: -20.16% (3Q2008)

Year-to-Date (as of 3/31/11): 3.35%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL EQUITY ALLOCATION FUND | Class III, GMO International Equity Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.21%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.21%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.01%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.72%

^[70]

Total annual operating expenses

rr_ExpensesOverAssets

0.73%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.72%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

116

^[4]

3 Years

rr_ExpenseExampleYear03

287

5 Years

rr_ExpenseExampleYear05

473

10 Years

rr_ExpenseExampleYear10

1,011

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

94

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

264

5 Years

rr_ExpenseExampleNoRedemptionYear05

447

10 Years

rr_ExpenseExampleNoRedemptionYear10

979

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(5.73%)

2002

rr_AnnualReturn2002

(0.40%)

2003

rr_AnnualReturn2003

48.51%

2004

rr_AnnualReturn2004

24.14%

2005

rr_AnnualReturn2005

18.72%

2006

rr_AnnualReturn2006

25.92%

2007

rr_AnnualReturn2007

17.44%

2008

rr_AnnualReturn2008

(41.39%)

2009

rr_AnnualReturn2009

28.07%

2010

rr_AnnualReturn2010

13.03%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

21.94%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(20.16%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.35%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL EQUITY ALLOCATION FUND | Return Before Taxes | Class III, GMO International Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

12.55%

5 Years

rr_AverageAnnualReturnYear05

4.55%

10 Years

rr_AverageAnnualReturnYear10

9.89%

Incept.

rr_AverageAnnualReturnSinceInception

8.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 11, 1996

GMO INTERNATIONAL EQUITY ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO International Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

12.29%

5 Years

rr_AverageAnnualReturnYear05

2.28%

10 Years

rr_AverageAnnualReturnYear10

8.11%

Incept.

rr_AverageAnnualReturnSinceInception

6.73%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 11, 1996

GMO INTERNATIONAL EQUITY ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

8.32%

5 Years

rr_AverageAnnualReturnYear05

3.51%

10 Years

rr_AverageAnnualReturnYear10

8.23%

Incept.

rr_AverageAnnualReturnSinceInception

6.83%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 11, 1996

GMO INTERNATIONAL EQUITY ALLOCATION FUND | MSCI ACWI ex-U.S. Index | Class III, GMO International Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI ACWI ex-U.S. Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.15%

5 Years

rr_AverageAnnualReturnYear05

4.82%

10 Years

rr_AverageAnnualReturnYear10

5.55%

Incept.

rr_AverageAnnualReturnSinceInception

5.93%

Inception Date

rr_AverageAnnualReturnInceptionDate

Oct. 11, 1996

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the MSCI EAFE Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 14% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

14.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), as well as to the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 19.55% (2Q2009)

Lowest Quarter: -18.80% (3Q2008)

Year-to-Date (as of 3/31/11): 2.96%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | Class III, GMO International Opportunities Equity Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.02%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.63%

^[71]

Total annual operating expenses

rr_ExpensesOverAssets

0.65%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.63%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

64

^[4]

3 Years

rr_ExpenseExampleYear03

217

5 Years

rr_ExpenseExampleYear05

383

10 Years

rr_ExpenseExampleYear10

864

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

64

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

217

5 Years

rr_ExpenseExampleNoRedemptionYear05

383

10 Years

rr_ExpenseExampleNoRedemptionYear10

864

Annual Total Returns

rr_BarChartTableAbstract

2007

rr_AnnualReturn2007

13.29%

2008

rr_AnnualReturn2008

(37.91%)

2009

rr_AnnualReturn2009

19.78%

2010

rr_AnnualReturn2010

10.86%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

19.55%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(18.80%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.96%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | Return Before Taxes | Class III, GMO International Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

10.86%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.29%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 05, 2006

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO International Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

10.65%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

(0.24%)

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 05, 2006

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO International Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

7.33%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.79%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 05, 2006

GMO INTERNATIONAL OPPORTUNITIES EQUITY ALLOCATION FUND | MSCI EAFE Index | Class III, GMO International Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI EAFE Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

7.75%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

0.31%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 05, 2006

GMO GLOBAL EQUITY ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO GLOBAL EQUITY ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the MSCI ACWI Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 6% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

6.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds and the U.S. Equity Funds (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund's primary exposure is to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., U.S. equity, foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of the underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of the Fund’s benchmark (which is a broad-based index) and a composite index computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 18.79% (2Q2003)

Lowest Quarter: -15.65% (4Q2008)

Year-to-Date (as of 3/31/11): 3.49%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO GLOBAL EQUITY ALLOCATION FUND | Class III, GMO Global Equity Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.13%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.13%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.02%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.58%

^[72]

Total annual operating expenses

rr_ExpensesOverAssets

0.60%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.02%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.58%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

86

^[4]

3 Years

rr_ExpenseExampleYear03

226

5 Years

rr_ExpenseExampleYear05

379

10 Years

rr_ExpenseExampleYear10

825

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

72

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

212

5 Years

rr_ExpenseExampleNoRedemptionYear05

363

10 Years

rr_ExpenseExampleNoRedemptionYear10

805

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(0.74%)

2002

rr_AnnualReturn2002

(6.23%)

2003

rr_AnnualReturn2003

38.23%

2004

rr_AnnualReturn2004

16.30%

2005

rr_AnnualReturn2005

11.32%

2006

rr_AnnualReturn2006

16.57%

2007

rr_AnnualReturn2007

9.57%

2008

rr_AnnualReturn2008

(33.09%)

2009

rr_AnnualReturn2009

24.50%

2010

rr_AnnualReturn2010

9.98%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter :

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

18.79%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(15.65%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date:

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.49%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO GLOBAL EQUITY ALLOCATION FUND | Return Before Taxes | Class III, GMO Global Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.69%

5 Years

rr_AverageAnnualReturnYear05

3.14%

10 Years

rr_AverageAnnualReturnYear10

6.87%

Incept.

rr_AverageAnnualReturnSinceInception

8.30%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 1996

GMO GLOBAL EQUITY ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO Global Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

9.45%

5 Years

rr_AverageAnnualReturnYear05

1.49%

10 Years

rr_AverageAnnualReturnYear10

5.38%

Incept.

rr_AverageAnnualReturnSinceInception

6.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 1996

GMO GLOBAL EQUITY ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Global Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.52%

5 Years

rr_AverageAnnualReturnYear05

2.40%

10 Years

rr_AverageAnnualReturnYear10

5.59%

Incept.

rr_AverageAnnualReturnSinceInception

6.22%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 1996

GMO GLOBAL EQUITY ALLOCATION FUND | MSCI ACWI Index (Fund benchmark) | Class III, GMO Global Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI ACWI Index (Fund benchmark)

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

12.67%

5 Years

rr_AverageAnnualReturnYear05

3.44%

10 Years

rr_AverageAnnualReturnYear10

3.20%

Incept.

rr_AverageAnnualReturnSinceInception

5.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 1996

GMO GLOBAL EQUITY ALLOCATION FUND | MSCI ACWI + Index (Composite index) | Class III, GMO Global Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI ACWI + Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

12.67%

5 Years

rr_AverageAnnualReturnYear05

2.24%

10 Years

rr_AverageAnnualReturnYear10

2.12%

Incept.

rr_AverageAnnualReturnSinceInception

5.37%

Inception Date

rr_AverageAnnualReturnInceptionDate

Nov. 26, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

MSCI ACWI + Index

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the MSCI World Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 20% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

20.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of the International Equity Funds and the U.S. Equity Funds (see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). The Fund also may invest in shares of other GMO Funds, including the Fixed Income Funds, Alpha Only Fund and Alternative Asset Opportunity Fund (the GMO Funds in which the Fund invests are collectively referred to herein as the “underlying Funds”). In addition, the Fund may hold securities directly. Although the Fund’s primary exposure is to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), the Fund also may have exposure to foreign and U.S. fixed income securities (including fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes. Under normal circumstances, the Fund invests (including through investment in the underlying Funds) at least 80% of its assets in equity investments (see “Name Policies”). The term “equity investments” refers to direct and indirect (e.g., through the underlying Funds) investments in common stocks and other stock-related securities, such as preferred stocks, convertible securities and depositary receipts.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., U.S. equity, foreign equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund’s holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Because the Fund and the underlying Funds normally do not take temporary defensive positions, declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund’s loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 14.41% (3Q2010)

Lowest Quarter: -15.27% (4Q2008)

Year-to-Date (as of 3/31/11): 3.34%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | Class III, GMO World Opportunities Equity Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.02%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.53%

^[73]

Total annual operating expenses

rr_ExpensesOverAssets

0.55%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.54%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

55

^[4]

3 Years

rr_ExpenseExampleYear03

184

5 Years

rr_ExpenseExampleYear05

324

10 Years

rr_ExpenseExampleYear10

733

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

55

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

184

5 Years

rr_ExpenseExampleNoRedemptionYear05

324

10 Years

rr_ExpenseExampleNoRedemptionYear10

733

Annual Total Returns

rr_BarChartTableAbstract

2006

rr_AnnualReturn2006

20.09%

2007

rr_AnnualReturn2007

10.03%

2008

rr_AnnualReturn2008

(32.08%)

2009

rr_AnnualReturn2009

19.93%

2010

rr_AnnualReturn2010

9.00%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.41%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Sep. 30, 2010

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(15.27%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

3.34%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | Return Before Taxes | Class III, GMO World Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

9.00%

5 Years

rr_AverageAnnualReturnYear05

3.25%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

4.76%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 16, 2005

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO World Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

8.75%

5 Years

rr_AverageAnnualReturnYear05

2.12%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 16, 2005

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO World Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

6.18%

5 Years

rr_AverageAnnualReturnYear05

2.59%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.87%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 16, 2005

GMO WORLD OPPORTUNITIES EQUITY ALLOCATION FUND | MSCI World Index | Class III, GMO World Opportunities Equity Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

2.43%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

3.88%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 16, 2005

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO GLOBAL BALANCED ASSET ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the GMO Global Balanced Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 32% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

32.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds’ Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund may be exposed to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), U.S. and foreign fixed income securities (including asset-backed securities and other fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, U.S. fixed income, foreign fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund’s holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund’s investments. The Manager, however, intends to invest at least 25% of the Fund’s assets in fixed income investments and at least 25% in equity investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund’s shares changes with the value of the Fund’s investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund’s investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager’s overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund’s shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund’s investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund’s total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO’s ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO’s proprietary investment techniques will fail to produce the desired results. The Fund’s portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager’s or another service provider’s internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund’s portfolio to be leveraged. Leverage increases the Fund’s portfolio losses when the value of its investments decline.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer’s failure to meet its payment obligations or the market’s expectation of a default, which may result from the downgrading of the issuer’s credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund’s securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund’s loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund’s investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund’s operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices, and composite indices, including the Fund’s benchmark, computed by the Manager. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices, and composite indices, including the Fund’s benchmark, computed by the Manager.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 14.27% (2Q2003)

Lowest Quarter: -9.87% (3Q2001)

Year-to-Date (as of 3/31/11): 2.60%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2009

^[74]

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Class III, GMO Global Balance Asset Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.10%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.10%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.01%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.53%

^[75]

Total annual operating expenses

rr_ExpensesOverAssets

0.54%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[76]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.53%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

75

^[4]

3 Years

rr_ExpenseExampleYear03

217

5 Years

rr_ExpenseExampleYear05

372

10 Years

rr_ExpenseExampleYear10

824

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

64

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

206

5 Years

rr_ExpenseExampleNoRedemptionYear05

360

10 Years

rr_ExpenseExampleNoRedemptionYear10

808

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

(1.52%)

2002

rr_AnnualReturn2002

3.15%

2003

rr_AnnualReturn2003

28.46%

2004

rr_AnnualReturn2004

13.44%

2005

rr_AnnualReturn2005

9.49%

2006

rr_AnnualReturn2006

12.11%

2007

rr_AnnualReturn2007

8.58%

2008

rr_AnnualReturn2008

(19.38%)

2009

rr_AnnualReturn2009

22.39%

2010

rr_AnnualReturn2010

7.38%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

14.27%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2003

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(9.87%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Sep. 30, 2001

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.60%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Return Before Taxes | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.17%

5 Years

rr_AverageAnnualReturnYear05

5.18%

10 Years

rr_AverageAnnualReturnYear10

7.63%

Incept.

rr_AverageAnnualReturnSinceInception

7.95%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

6.70%

5 Years

rr_AverageAnnualReturnYear05

3.22%

10 Years

rr_AverageAnnualReturnYear10

5.86%

Incept.

rr_AverageAnnualReturnSinceInception

5.74%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

4.81%

5 Years

rr_AverageAnnualReturnYear05

3.55%

10 Years

rr_AverageAnnualReturnYear10

5.77%

Incept.

rr_AverageAnnualReturnSinceInception

5.73%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | MSCI ACWI Index | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI ACWI Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

12.67%

5 Years

rr_AverageAnnualReturnYear05

3.44%

10 Years

rr_AverageAnnualReturnYear10

3.20%

Incept.

rr_AverageAnnualReturnSinceInception

5.62%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Barclays Capital U.S. Aggregate Index | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Aggregate Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.54%

5 Years

rr_AverageAnnualReturnYear05

5.80%

10 Years

rr_AverageAnnualReturnYear10

5.84%

Incept.

rr_AverageAnnualReturnSinceInception

6.35%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Barclays Capital U.S. Aggregate Index

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | GMO Global Balanced Index (Fund benchmark) | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

GMO Global Balanced Index (Fund benchmark)

1 Year

rr_AverageAnnualReturnYear01

11.05%

5 Years

rr_AverageAnnualReturnYear05

4.31%

10 Years

rr_AverageAnnualReturnYear10

3.98%

Incept.

rr_AverageAnnualReturnSinceInception

6.61%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

GMO Global Balanced Index

GMO GLOBAL BALANCED ASSET ALLOCATION FUND | Global Balanced Benchmark+ Index (Composite index) | Class III, GMO Global Balance Asset Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Global Balanced Benchmark+ Index (Composite index)

1 Year

rr_AverageAnnualReturnYear01

11.05%

5 Years

rr_AverageAnnualReturnYear05

4.31%

10 Years

rr_AverageAnnualReturnYear10

2.49%

Incept.

rr_AverageAnnualReturnSinceInception

5.12%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jun. 28, 1996

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Global Balanced Benchmark+ Index

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Total return greater than that of its benchmark, the GMO Strategic Opportunities Allocation Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 36% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

36.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund may have exposure to foreign and U.S. equity investments (which may include emerging country equities, both growth and value style equities and equities of any market capitalization), U.S. and foreign fixed income securities (including asset-backed securities and other fixed income securities of any credit quality and having any maturity or duration), the investment returns of commodities and, from time to time, other alternative asset classes.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, U.S. fixed income, foreign fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices and the Fund’s benchmark (which is a composite index computed by the Manager). Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of broad-based indices and the Fund’s benchmark (which is a composite index computed by the Manager).

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 11.73% (2Q2009)

Lowest Quarter: -10.19% (4Q2008)

Year-to-Date (as of 3/31/11): 2.98%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | Class III, GMO Strategic Opportunities Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.01%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.54%

^[77]

Total annual operating expenses

rr_ExpensesOverAssets

0.55%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.54%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

55

^[4]

3 Years

rr_ExpenseExampleYear03

190

5 Years

rr_ExpenseExampleYear05

338

10 Years

rr_ExpenseExampleYear10

767

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

55

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

190

5 Years

rr_ExpenseExampleNoRedemptionYear05

338

10 Years

rr_ExpenseExampleNoRedemptionYear10

767

Annual Total Returns

rr_BarChartTableAbstract

2006

rr_AnnualReturn2006

16.77%

2007

rr_AnnualReturn2007

9.07%

2008

rr_AnnualReturn2008

(21.40%)

2009

rr_AnnualReturn2009

21.13%

2010

rr_AnnualReturn2010

7.96%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

11.73%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(10.19%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 31, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

2.98%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | Return Before Taxes | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

7.96%

5 Years

rr_AverageAnnualReturnYear05

5.53%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

6.72%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

7.57%

5 Years

rr_AverageAnnualReturnYear05

3.86%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.09%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

5.42%

5 Years

rr_AverageAnnualReturnYear05

4.03%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.08%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | MSCI World Index | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

2.43%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

4.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | Barclays Capital U.S. Aggregate Index | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Barclays Capital U.S. Aggregate Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

6.54%

5 Years

rr_AverageAnnualReturnYear05

5.80%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

5.26%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Barclays Capital U.S. Aggregate Index (reflects no deduction for fees, expenses, or taxes)

GMO STRATEGIC OPPORTUNITIES ALLOCATION FUND | GMO Strategic Opportunities Allocation Index (Fund benchmark) | Class III, GMO Strategic Opportunities Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

GMO Strategic Opportunities Allocation Index (Fund benchmark)

1 Year

rr_AverageAnnualReturnYear01

10.90%

5 Years

rr_AverageAnnualReturnYear05

3.63%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

4.76%

Inception Date

rr_AverageAnnualReturnInceptionDate

May 31, 2005

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

GMO Strategic Opportunities Allocation Index

GMO BENCHMARK-FREE ALLOCATION FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO BENCHMARK-FREE ALLOCATION FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks a positive total return. The Fund does not have a particular securities market index as a benchmark and does not seek to outperform a particular index or blend of indices (i.e., the Fund seeks positive return, not “relative” return).

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

^[78]

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amount has been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do not sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund operating expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 19% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

19.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund is a fund of funds and invests primarily in shares of other GMO Funds, which may include the International Equity Funds, the U.S. Equity Funds, the Fixed Income Funds, Alpha Only Fund, Alternative Asset Opportunity Fund, Debt Opportunities Fund, High Quality Short-Duration Bond Fund, Special Situations Fund and World Opportunity Overlay Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may hold securities (particularly asset-backed securities) directly or through one or more subsidiaries or other entities. The Fund implements its strategy by allocating its assets among asset classes represented by the underlying Funds (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities). The Fund is not restricted in its exposure to any particular asset class, and at times may be substantially invested in underlying Funds that primarily invest in a single asset class (e.g., Fixed Income Funds). In addition, the Fund is not restricted in its exposure to any particular market. Although the Fund generally will have exposure to both emerging countries and developed countries, including the U.S., at times, it also may have substantial exposure to a particular country or type of country (e.g., emerging countries).

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity, emerging country debt, foreign fixed income, U.S. fixed income and commodities) to select the underlying Funds in which the Fund invests and to decide how much to invest in each. The Manager changes the Fund's holdings of underlying Funds in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments. The Manager's ability to shift investments among the underlying Funds is not subject to any limits. The Fund may invest substantially all of its assets in a few underlying Funds that primarily invest in the same asset class and may, at times, also invest a substantial portion of its assets in a single underlying Fund.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. An underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. Declines in stock market prices generally are likely to reduce the net asset value of the Fund's shares.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk — Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening of credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of companies with smaller market capitalizations often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalization.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent the Fund or an underlying Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests do not perform as expected. Because the Fund bears the fees and expenses of the underlying Funds in which it invests, new investments in underlying Funds with higher fees or expenses than those of the underlying Funds in which the Fund is currently invested will increase the Fund's total expenses. The fees and expenses associated with an investment in the Fund are less predictable and may be higher than fees and expenses associated with an investment in funds that charge a fixed management fee.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating. Below investment grade securities have speculative characteristics, and changes in economic conditions or other circumstances are more likely to impair the capacity of issuers to make principal and interest payments than is the case with issuers of investment grade securities.

• Counterparty Risk – The Fund runs the risk that the counterparty to an over-the-counter (OTC) derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Commodities Risk – To the extent an underlying Fund has exposure to global commodity markets, the value of its shares is affected by factors particular to the commodity markets and may fluctuate more than the value of shares of a fund with a broader range of investments.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives and securities lending may cause the Fund's portfolio to be leveraged. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Short Sales Risk – The Fund runs the risk that an underlying Fund's loss on a short sale of securities that the underlying Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

Some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by those Funds may affect their performance more than if they were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Consumer Price Index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index and the Consumer Price Index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table are lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 9.19% (2Q2009)

Lowest Quarter: -6.90% (4Q2008)

Year-to-Date (as of 3/31/11): 1.92%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO BENCHMARK-FREE ALLOCATION FUND | Class III, GMO Benchmark-Free Allocation Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

0.09%

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

0.09%

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

none

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.02%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.57%

^[79]

Total annual operating expenses

rr_ExpensesOverAssets

0.59%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[69]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.58%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

78

^[4]

3 Years

rr_ExpenseExampleYear03

252

5 Years

rr_ExpenseExampleYear05

442

10 Years

rr_ExpenseExampleYear10

991

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

68

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

242

5 Years

rr_ExpenseExampleNoRedemptionYear05

431

10 Years

rr_ExpenseExampleNoRedemptionYear10

977

Annual Total Returns

rr_BarChartTableAbstract

2004

rr_AnnualReturn2004

18.15%

2005

rr_AnnualReturn2005

16.44%

2006

rr_AnnualReturn2006

12.93%

2007

rr_AnnualReturn2007

11.28%

2008

rr_AnnualReturn2008

(11.23%)

2009

rr_AnnualReturn2009

20.65%

2010

rr_AnnualReturn2010

4.91%

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

9.19%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2009

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(6.90%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Dec. 03, 2008

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

1.92%

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO BENCHMARK-FREE ALLOCATION FUND | Return Before Taxes | Class III, GMO Benchmark-Free Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

4.72%

5 Years

rr_AverageAnnualReturnYear05

7.11%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

12.00%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 2003

GMO BENCHMARK-FREE ALLOCATION FUND | Return After Taxes on Distributions | Class III, GMO Benchmark-Free Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

4.19%

5 Years

rr_AverageAnnualReturnYear05

4.42%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.27%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 2003

GMO BENCHMARK-FREE ALLOCATION FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Benchmark-Free Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

3.14%

5 Years

rr_AverageAnnualReturnYear05

4.86%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

9.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 2003

GMO BENCHMARK-FREE ALLOCATION FUND | MSCI World Index | Class III, GMO Benchmark-Free Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

MSCI World Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(returns reflect no deduction for fees or expenses, but are net of withholding tax on dividend reinvestments)

1 Year

rr_AverageAnnualReturnYear01

11.76%

5 Years

rr_AverageAnnualReturnYear05

2.43%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

7.14%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 2003

GMO BENCHMARK-FREE ALLOCATION FUND | Consumer Price Index | Class III, GMO Benchmark-Free Allocation Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Consumer Price Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

1.25%

5 Years

rr_AverageAnnualReturnYear05

2.18%

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.47%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 23, 2003

Performance Additional Market Index [Text]

rr_PerformanceAdditionalMarketIndex

Consumer Price Index

GMO ALPHA ONLY FUND | GMO Trust

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

GMO ALPHA ONLY FUND

Objective [Heading]

rr_ObjectiveHeading

Investment objective

Objective Primary [Text Block]

rr_ObjectivePrimaryTextBlock

Seeks to outperform the Fund’s benchmark, the Citigroup 3-Month Treasury Bill Index.

Fees and expenses

gmofx_FundFeesAndExpensesAbstract

Expense [Heading]

rr_ExpenseHeading

Fees and expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

The tables below describe the fees and expenses that you may pay if you buy and hold shares of the Fund.

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder fees (fees paid directly from your investment)

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

Annual Fund operating expenses (expenses that you pay each year as a percentage of the value of your investment)

Expenses Restated to Reflect Current [Text]

rr_ExpensesRestatedToReflectCurrent

The amounts have been restated to reflect current fees of certain underlying funds.

Fee Waiver or Reimbursement over Assets, Date of Termination

rr_FeeWaiverOrReimbursementOverAssetsDateOfTermination

June 30, 2012

Example

rr_ExpenseExampleAbstract

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

This example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The example assumes that you invest $10,000 in the Fund for the time periods indicated. The example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same as those shown in the table. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

Expense Example by, Year, Caption [Text]

rr_ExpenseExampleByYearCaption

If you sell your shares

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Caption [Text]

rr_ExpenseExampleNoRedemptionByYearCaption

If you do no sell your shares

Portfolio turnover

gmofx_PortfolioTurnoverAltAbstract

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The Fund pays transaction costs, such as commissions, when it buys and sells securities. A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in Annual Fund Operating Expenses or in the Example, affect the Fund’s performance. During its fiscal year ended February 28, 2011, the Fund’s portfolio turnover rate (excluding short-term investments) was 89% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

89.00%

Strategy [Heading]

rr_StrategyHeading

Principal investment strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The Fund's investment program involves having both long and short investment exposures. The Fund seeks to construct a portfolio in which it has long investment exposure to asset classes and sub-asset classes that it expects will outperform relative to the asset classes and sub-asset classes to which it has short investment exposure.

To gain long investment exposure, the Fund invests primarily in shares of the U.S. Equity Funds and the International Equity Funds, and also may invest in shares of Emerging Country Debt Fund (collectively, the “underlying Funds”) (see “Additional Information About the Funds' Investment Strategies, Risks, and Expenses – Asset Allocation Funds”). In addition, the Fund may gain long investment exposure by investing in securities directly, rather than through the underlying Funds.

To gain short investment exposure, the Fund may use over-the-counter (“OTC”) and exchange-traded derivatives (including futures, swap contracts and currency forwards) and make short sales of securities (e.g., shares of exchange-traded funds), including short sales of securities the Fund does not own. The Fund is not limited in its use of derivatives or in the absolute face value of its derivatives positions, and, as a result, the Fund may be leveraged in relation to its assets.

The Manager uses multi-year forecasts of relative value and risk among asset classes (e.g., foreign equity, U.S. equity, emerging country equity and emerging country debt) and sub-asset classes (e.g., small- to mid-cap stocks in the foreign equity asset class and quality stocks in the U.S. equity and emerging country equity asset classes) to select the underlying Funds and securities in which the Fund invests or takes short positions and to decide how much to invest and/or short in each. The Manager changes the Fund's holdings in response to changes in its investment outlook and market valuations and may use redemption/purchase activity to rebalance the Fund's investments.

For cash management purposes, the Fund may invest in U.S. Treasury Fund and unaffiliated money market funds.

Risk [Heading]

rr_RiskHeading

Principal risks of investing in the Fund

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

The value of the Fund's shares changes with the value of the Fund's investments. Many factors can affect this value, and you may lose money by investing in the Fund. References to investments include those held directly by the Fund and indirectly through the Fund's investments in the underlying Funds. The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund's or the underlying Fund's performance more than if the Fund or the underlying Fund were diversified. The principal risks of investing in the Fund are summarized below. For a more complete discussion of these risks, including those risks to which the Fund is exposed as a result of its investments in the underlying Funds, see “Description of Principal Risks.”

• Derivatives Risk – The use of derivatives involves the risk that their value may not move as expected relative to the value of the relevant underlying assets, rates or indices. Derivatives also present other Fund risks, including market risk, liquidity risk, currency risk and counterparty risk.

• Foreign Investment Risk – The market prices of many foreign securities fluctuate more than those of U.S. securities. Many foreign markets are less stable, smaller, less liquid and less regulated than U.S. markets, and the cost of trading in those markets often is higher than in U.S. markets. Foreign portfolio transactions generally involve higher commission rates, transfer taxes and custodial costs than similar transactions in the U.S. In addition, the Fund may be subject to foreign taxes on capital gains or other income payable on foreign securities, on transactions in those securities and on the repatriation of proceeds generated from those securities. Also, many foreign markets require a license for the Fund to invest directly in those markets, and the Fund is subject to the risk that it could not invest if its license were terminated or suspended. In some foreign markets, prevailing custody and trade settlement practices (e.g., the requirement to pay for securities prior to receipt) expose the Fund to credit and other risks with respect to participating brokers, custodians, clearing banks or other clearing agents, escrow agents and issuers. Further, adverse changes in investment regulations, capital requirements or exchange controls could adversely affect the value of the Fund's investments. These and other risks (e.g., nationalization, expropriation or other confiscation of assets of foreign issuers) tend to be greater for investments in companies tied economically to emerging countries, the economies of which tend to be more volatile than the economies of developed countries.

• Market Risk – Equity Securities – The market value of equity investments may decline due to factors affecting the issuing companies, their industries, or the economy and equity markets generally. If the Fund or an underlying Fund purchases equity investments at a discount from their value as determined by the Manager, the Fund runs the risk that the market prices of these investments will not increase to that value for a variety of reasons, one of which may be the Manager's overestimation of the value of those investments. The Fund or an underlying Fund also may purchase equity investments that typically trade at higher multiples of current earnings than other securities, and the market values of these investments often are more sensitive to changes in future earnings expectations than those other securities. In addition, the value of the Fund's shares will be adversely affected if the equity investments that are the subject of the Fund's short positions appreciate in value.

• Liquidity Risk – Low trading volume, lack of a market maker, large size of position or legal restrictions may limit or prevent a Fund from selling particular securities or unwinding derivative positions at desirable prices. The more less-liquid securities the Fund holds, the more likely it is to honor a redemption request in-kind.

• Fund of Funds Risk – The Fund is indirectly exposed to all of the risks of an investment in the underlying Funds, including the risk that the underlying Funds in which it invests will not perform as expected or that the Fund will invest in underlying funds with higher fees or expenses.

• Market Risk – Fixed Income Securities – Typically, the market value of fixed income securities will decline during periods of rising interest rates and widening credit spreads.

• Market Risk – Asset-Backed Securities – Asset-backed securities are subject to severe credit downgrades, illiquidity, defaults and declines in market value.

• Leveraging Risk – The use of reverse repurchase agreements and other derivatives may cause the Fund's portfolio to be leveraged. The Fund and some underlying Funds are not limited in the extent to which they may use derivatives or in the absolute face value of their derivative positions. Leverage increases the Fund's portfolio losses when the value of its investments decline.

• Management and Operational Risk – The Fund relies on GMO's ability to achieve its investment objective by effectively implementing its investment approach. The Fund runs the risk that GMO's proprietary investment techniques will fail to produce the desired results. The Fund's portfolio managers may use quantitative analyses and/or models and any imperfections or limitations in such analyses and/or models could affect the ability of the portfolio managers to implement strategies. By necessity, these analyses and models make simplifying assumptions that limit their efficacy. Models that appear to explain prior market data can fail to predict future market events. Further, the data used in models may be inaccurate and/or it may not include the most recent information about a company or a security. The Fund is also subject to the risk that deficiencies in the Manager's or another service provider's internal systems or controls will cause losses for the Fund or impair Fund operations.

• Currency Risk – Fluctuations in exchange rates can adversely affect the market value of foreign currency holdings and investments denominated in foreign currencies, or that the U.S. dollar will decline in value relative to the foreign currency being hedged.

• Credit Risk – The Fund runs the risk that the issuer or guarantor of a fixed income security or the obligor of an obligation underlying an asset-backed security will be unable or unwilling to satisfy its obligations to pay principal or interest payments or to otherwise honor its obligations. The market value of a fixed income security normally will decline as a result of the issuer's failure to meet its payment obligations or the market's expectation of a default, which may result from the downgrading of the issuer's credit rating.

• Counterparty Risk – The Fund runs the risk that the counterparty to an OTC derivatives contract or a borrower of the Fund's securities will be unable or unwilling to make timely settlement payments or otherwise honor its obligations.

• Real Estate Risk – To the extent an underlying Fund concentrates its assets in real estate-related investments, the value of its portfolio is subject to factors affecting the real estate industry and may fluctuate more than the value of a portfolio that consists of securities of companies in a broader range of industries.

• Smaller Company Risk – Smaller companies may have limited product lines, markets or financial resources, may lack the competitive strength of larger companies, or may lack managers with experience or depend on a few key employees. The securities of small- and mid-cap companies often are less widely held and trade less frequently and in lesser quantities, and their market prices often fluctuate more, than the securities of companies with larger market capitalizations.

• Short Sales Risk – The Fund runs the risk that the Fund's loss on a short sale of securities that the Fund does not own is unlimited.

• Focused Investment Risk – Focusing investments in countries, regions, sectors or companies or in industries with high positive correlations to one another creates additional risk.

• Market Disruption and Geopolitical Risk – Geopolitical and other events may disrupt securities markets and adversely affect global economies and markets. Those events as well as other changes in foreign and domestic economic and political conditions could adversely affect the value of the Fund's investments.

• Large Shareholder Risk – To the extent that shares of the Fund are held by large shareholders (e.g., institutional investors, asset allocation funds, or other GMO Funds), the Fund is subject to the risk that these shareholders will disrupt the Fund's operations by purchasing or redeeming Fund shares in large amounts and/or on a frequent basis.

Risk Lose Money [Text]

rr_RiskLoseMoney

Many factors can affect this value, and you may lose money by investing in the Fund.

Risk Nondiversified Status [Text]

rr_RiskNondiversifiedStatus

The Fund and some of the underlying Funds are non-diversified investment companies under the Investment Company Act of 1940, as amended, and therefore a decline in the market value of a particular security held by the Fund or an underlying Fund may affect the Fund's or the underlying Fund's performance more than if the Fund or the underlying Fund were diversified.

Performance

gmofx_FundPastPerformanceAbstract

Bar Chart And Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index. Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart. Returns in the table reflect current purchase premiums and redemption fees. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account). After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary. Past performance (before and after taxes) is not an indication of future performance.

Performance Information Illustrates Variability Of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart and table below provide some indication of the risks of investing in the Fund by showing changes in the Fund’s annual total returns from year to year for the periods indicated and by comparing the Fund’s average annual total returns for different calendar periods with those of a broad-based index.

Bar Chart Does Not Reflect Sales Loads [Text]

rr_BarChartDoesNotReflectSalesLoads

Purchase premiums and redemption fees are not reflected in the bar chart, but are reflected in the table; as a result, the returns in the table may be lower than the returns in the bar chart.

Performance Table Does Reflect Sales Loads

rr_PerformanceTableDoesReflectSalesLoads

Returns in the table reflect current purchase premiums and redemption fees.

Performance Table Uses Highest Federal Rate

rr_PerformanceTableUsesHighestFederalRate

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant To Tax Deferred

rr_PerformanceTableNotRelevantToTaxDeferred

Actual after-tax returns depend on your tax situation and may differ from those shown. After-tax returns shown are not relevant if you are tax-exempt or if you hold your Fund shares through tax-deferred arrangements (such as a 401(k) plan or individual retirement account).

Performance Table One Class Of After Tax Shown [Text]

rr_PerformanceTableOneClassOfAfterTaxShown

After-tax returns are shown for Class III shares only; after-tax returns for other classes will vary.

Performance Past Does Not Indicate Future [Text]

rr_PerformancePastDoesNotIndicateFuture

Past performance (before and after taxes) is not an indication of future performance.

Annual Total Returns

rr_BarChartTableAbstract

Bar Chart [Heading]

rr_BarChartHeading

Annual Total Returns/Class III Shares Years Ending December 31

Bar Chart Closing [Text Block]

rr_BarChartClosingTextBlock

Highest Quarter: 7.39% (1Q2001)

Lowest Quarter: -4.81% (2Q2009)

Year-to-Date (as of 3/31/11): -1.43%

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Performance Table Heading

rr_PerformanceTableHeading

Average Annual Total Returns Periods Ending December 31, 2010

GMO ALPHA ONLY FUND | Class III, GMO Alpha Only Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class III

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class III

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.15%

^[80]

Other expenses

rr_OtherExpensesOverAssets

0.04%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.44%

^[81]

Total annual operating expenses

rr_ExpensesOverAssets

1.13%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.46%)

^[80]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.67%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class III

1 Year

rr_ExpenseExampleYear01

68

^[4]

3 Years

rr_ExpenseExampleYear03

320

5 Years

rr_ExpenseExampleYear05

591

10 Years

rr_ExpenseExampleYear10

1,365

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class III

1 Year

rr_ExpenseExampleNoRedemptionYear01

68

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

320

5 Years

rr_ExpenseExampleNoRedemptionYear05

591

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,365

Annual Total Returns

rr_BarChartTableAbstract

2001

rr_AnnualReturn2001

15.10%

2002

rr_AnnualReturn2002

11.63%

2003

rr_AnnualReturn2003

2.71%

2004

rr_AnnualReturn2004

2.64%

2005

rr_AnnualReturn2005

4.95%

2006

rr_AnnualReturn2006

3.34%

2007

rr_AnnualReturn2007

7.60%

2008

rr_AnnualReturn2008

12.08%

2009

rr_AnnualReturn2009

(7.93%)

2010

rr_AnnualReturn2010

(4.02%)

Highest Quarterly Return, Label

rr_HighestQuarterlyReturnLabel

Highest Quarter:

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

7.39%

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Mar. 31, 2001

Lowest Quarterly Return, Label

rr_LowestQuarterlyReturnLabel

Lowest Quarter:

Lowest Quarterly Return, Return

rr_BarChartLowestQuarterlyReturn

(4.81%)

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2009

Year To Date Return, Label

rr_YearToDateReturnLabel

Year-to-Date

Bar Chart, Year To Date Return

rr_BarChartYearToDateReturn

(1.43%)

Bar Chart, Year To Date Return, Date

rr_BarChartYearToDateReturnDate

Mar. 31, 2011

GMO ALPHA ONLY FUND | Class IV, GMO Alpha Only Fund

Shareholder fees

rr_ShareholderFeesAbstract

Shareholder Fees Column [Text]

rr_ShareholderFeesColumnName

Class IV

Purchase premium (as a percentage of amount invested)

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Redemption fee (as a percentage of amount redeemed)

rr_RedemptionFeeOverRedemption

none

Annual Fund operating expenses

rr_OperatingExpensesAbstract

Operating Expenses Column [Text]

rr_OperatingExpensesColumnName

Class IV

Management fee

rr_ManagementFeesOverAssets

0.50%

Shareholder service fee

rr_DistributionOrSimilarNon12b1FeesOverAssets

0.10%

^[80]

Other expenses

rr_OtherExpensesOverAssets

0.04%

Acquired fund fees and expenses (underlying fund expenses)

rr_AcquiredFundFeesAndExpensesOverAssets

0.44%

^[81]

Total annual operating expenses

rr_ExpensesOverAssets

1.08%

Expense reimbursement

rr_FeeWaiverOrReimbursementOverAssets

(0.46%)

^[80]

Total annual operating expenses after expense reimbursement

rr_NetExpensesOverAssets

0.62%

Example

rr_ExpenseExampleAbstract

Expense Example, By Year, Column [Text]

rr_ExpenseExampleByYearColumnName

Class IV

1 Year

rr_ExpenseExampleYear01

63

^[4]

3 Years

rr_ExpenseExampleYear03

304

5 Years

rr_ExpenseExampleYear05

564

10 Years

rr_ExpenseExampleYear10

1,308

Expense Example, No Redemption

rr_ExpenseExampleNoRedemptionAbstract

Expense Example, No Redemption, By Year, Column [Text]

rr_ExpenseExampleNoRedemptionByYearColumnName

Class IV

1 Year

rr_ExpenseExampleNoRedemptionYear01

63

^[4]

3 Years

rr_ExpenseExampleNoRedemptionYear03

304

5 Years

rr_ExpenseExampleNoRedemptionYear05

564

10 Years

rr_ExpenseExampleNoRedemptionYear10

1,308

GMO ALPHA ONLY FUND | Return Before Taxes | Class III, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(4.02%)

5 Years

rr_AverageAnnualReturnYear05

1.95%

10 Years

rr_AverageAnnualReturnYear10

4.59%

Incept.

rr_AverageAnnualReturnSinceInception

4.18%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1994

GMO ALPHA ONLY FUND | Return Before Taxes | Class IV, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Return Before Taxes

1 Year

rr_AverageAnnualReturnYear01

(3.98%)

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

1.80%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 02, 2006

GMO ALPHA ONLY FUND | Return After Taxes on Distributions | Class III, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions

1 Year

rr_AverageAnnualReturnYear01

(4.02%)

5 Years

rr_AverageAnnualReturnYear05

(2.36%)

10 Years

rr_AverageAnnualReturnYear10

1.86%

Incept.

rr_AverageAnnualReturnSinceInception

1.64%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1994

GMO ALPHA ONLY FUND | Return After Taxes on Distributions and Sale of Fund Shares | Class III, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Return After Taxes on Distributions and Sale of Fund Shares

1 Year

rr_AverageAnnualReturnYear01

(2.62%)

5 Years

rr_AverageAnnualReturnYear05

2.55%

10 Years

rr_AverageAnnualReturnYear10

3.77%

Incept.

rr_AverageAnnualReturnSinceInception

3.05%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1994

GMO ALPHA ONLY FUND | Citigroup 3-Month Treasury Bill Index | Class III, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class III

Label

rr_AverageAnnualReturnLabel

Citigroup 3-Month Treasury Bill Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.13%

5 Years

rr_AverageAnnualReturnYear05

2.30%

10 Years

rr_AverageAnnualReturnYear10

2.26%

Incept.

rr_AverageAnnualReturnSinceInception

3.44%

Inception Date

rr_AverageAnnualReturnInceptionDate

Jul. 29, 1994

GMO ALPHA ONLY FUND | Citigroup 3-Month Treasury Bill Index | Class IV, GMO Alpha Only Fund

Average Annual Total Returns

rr_AverageAnnualReturnAbstract

Column

rr_AverageAnnualReturnColumnName

Class IV

Label

rr_AverageAnnualReturnLabel

Citigroup 3-Month Treasury Bill Index

Index No Deduction For Fees, Expenses, Taxes [Text]

rr_IndexNoDeductionForFeesExpensesTaxes

(reflects no deduction for fees, expenses, or taxes)

1 Year

rr_AverageAnnualReturnYear01

0.13%

5 Years

rr_AverageAnnualReturnYear05

10 Years

rr_AverageAnnualReturnYear10

Incept.

rr_AverageAnnualReturnSinceInception

2.23%

Inception Date

rr_AverageAnnualReturnInceptionDate

Mar. 02, 2006

[1] The Fund is the successor to GMO U.S. Core Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO U.S. Core Fund and reflects GMO U.S. Core Fund's annual operating expenses (0.02% higher than those of the Fund). As of the date of this Prospectus, no Class V shares of the Fund or its predecessor have been outstanding since February 11, 2005. Class V shares would be invested in the same portfolio of securities as Class III shares. Annual returns would principally differ to the extent Class V shares do not have the same expenses as Class III shares.

[2] The Fund is the successor to GMO U.S. Core Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO U.S. Core Fund and reflects GMO U.S. Core Fund's annual operating expenses (0.02% higher than those of the Fund).

[3] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[4] After reimbursement

[5] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[6] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.33% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[7] The Fund is the successor to GMO Intrinsic Value Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Intrinsic Value Fund and reflects GMO Intrinsic Value Fund's annual operating expenses (0.02% higher than those of the Fund).

[8] The Fund is the successor to GMO Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Growth Fund and reflects GMO Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[9] "Other expenses" have been restated to reflect current fees.

[10] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.31% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[11] The Fund is the successor to GMO Small/Mid Cap Value Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Small/Mid Cap Value Fund and reflects GMO Small/Mid Cap Value Fund's annual operating expenses (0.02% higher than those of the Fund).

[12] The Fund is the successor to GMO Small/Mid Cap Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO Small/Mid Cap Growth Fund and reflects GMO Small/Mid Cap Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[13] The Fund is the successor to GMO International Disciplined Equity Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO International Disciplined Equity Fund and reflects GMO International Disciplined Equity Fund's annual operating expenses (0.02% higher than those of the Fund).

[14] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.38% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[15] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[16] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[17] The amounts represent an annualized estimate of the Fund's operating expenses for its initial fiscal year.

[18] The Fund is the successor to GMO International Growth Fund, a former series of GMO Trust that had an investment objective and policies and restrictions substantially identical to those of the Fund. Performance of the Fund through September 16, 2005 is that of GMO International Growth Fund and reflects GMO International Growth Fund's annual operating expenses (0.02% higher than those of the Fund).

[19] An additional purchase premium and redemption fee of 0.005% is charged for any purchases/redemptions (or any portion of a purchase/redemption) effected in a currency other than the U.S. dollar.

[20] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.45% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[21] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[22] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under 'Expense Reimbursement' in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[23] Information on the Fund's return after taxes is unavailable prior to June 28, 1996, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[24] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.60% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[25] Performance of Class III shares prior to June 28, 1996 is that of the private investment pool and reflects the pool's higher annual operating expenses. The pool was not registered as an investment company and therefore was not subject to restrictions imposed on the Fund by the Investment Company Act of 1940 and the Internal Revenue Code of 1986. Had the pool been subject to these restrictions, its performance may have been adversely affected.

[26] Information on the Fund's return after taxes is unavailable prior to June 30, 2000, the date the Fund commenced operations as a registered investment company. Prior to that date, the Fund operated as a private investment pool with investment objectives, policies, and guidelines that were substantially the same as those of the Fund.

[27] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.70% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without consent by the Fund's Board of Trustees.

[28] Performance of Class III shares prior to June 30, 2000 is that of the private investment pool, restated to reflect the Fund's higher annual operating expenses. The pool was not registered as an investment company and therefore was not subject to certain restrictions imposed on the Fund by the Investment Company Act of 1940 and the Internal Revenue Code of 1986. Had the pool been subject to these restrictions, its performance may have been adversely affected.

[29] For the period from March 16, 2009 to August 12, 2009, no Class IV shares were outstanding. The returns shown in the table for that period are those of Class III shares, which have higher expenses.

[30] Applies only to shares acquired on or after June 1, 1995 (including shares acquired by reinvestment of dividends or other distribution). With respect to Class III shares purchased through third-party intermediaries and any shares acquired prior to March 27, 2002, the level of redemption fee charged by the Fund is 0.40%.

[31] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were approximately 0.01% and less than 0.01%, respectively.

[32] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse each class of the Fund to the extent the class's total annual operating expenses exceed the following amounts of the class's average daily net assets: 0.95% for Class II shares, 0.90% for Class III shares, 0.85% for Class IV shares, 0.80% for Class V shares, and 0.77% for Class VI shares. Excluded Fund Fees and Expenses include underlying fund expenses, custodial fees, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[33] For the period from January 9, 1998 to August 12, 2009, no Class II shares were outstanding. The returns shown in the table for that period are those of Class III shares, which have been adjusted downward to reflect Class II's higher total annual operating expenses (Class II's expenses during these periods were calculated by adjusting Class III's actual total annual operating expenses during such periods upward by the current differential between "Total annual operating expenses" for Class II and Class III shares shown in the Fund's "Annual Fund operating expenses" table).

[34] For the period from October 26, 2004 to February 11, 2005, no Class V shares were outstanding. The returns shown in the table for that period are those of Class IV shares, which have higher expenses.

[35] These indirect expenses include commission fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.01% and 0.01%, respectively.

[36] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 1.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[37] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 1.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include administration fees, distribution (12b-1) fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[38] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.75% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, all of a portion of the Fund's custodial fee (up to 10% per annum), independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[39] For periods prior to the public offering of the Fund's shares, which began on October 29, 2009, the Fund's after-tax returns reflect dividends that included certain non-deductible investment expenses.

[40] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.55% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[41] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.54% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.54% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[42] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.10% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its direct or indirect investment in U.S. Treasury Fund (excluding U.S. Treasury Fund's Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.10% of the Fund's average daily net assets. These contractual expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[43] The amounts have been restated to reflect current fees of certain underlying funds.

[44] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[45] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.01%, respectively.

[46] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by the Fund exceeds 0.15%; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[47] "Other expenses" have been restated to reflect current fees. The amount includes interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.20% and 0.01%, respectively.

[48] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.03%, 0.01%, and 0.03%, respectively.

[49] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.02%, 0.01%, and less than 0.01%, respectively.

[50] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.03%, 0.01%, and 0.01%, respectively.

[51] The amount includes interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.11% and 0.01%, respectively.

[52] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.01%, respectively.

[53] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above.

[54] "Other expenses" have been restated to reflect current fees. The amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.09% and 0.06%, respectively.

[55] The amount has been restated to reflect current fees of certain underlying funds.

[56] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.05% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. In addition, the Manager has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.05% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without consent by the Fund's Board of Trustees.

[57] For the period from April 18, 1990 until June 30, 1991, the Fund operated as a money market fund.

[58] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[59] The amounts reflect the indirect net expenses associated with the Fund's investment in Short-Duration Collateral Fund ("SDCF").

[60] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.05% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. In addition, the Manager has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in SDCF and other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.05% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[61] As of the date of this Prospectus, no Class VI shares of the Fund have been outstanding since February 27, 2007. The returns shown in the table for that period are those of Class III shares, which have higher expenses than Class VI shares.

[62] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed 0.15%. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.25% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Fund's Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.25% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[63] "Other expenses" have been restated to reflect current fees. These amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were approximately 0.19% and less than 0.01%, respectively.

[64] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were 0.02%, 0.01%, and 0.05%, respectively.

[65] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.08% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[66] The amounts include interest expense incurred by the Fund as a result of entering into reverse repurchase agreements. "Other expenses" (before addition of interest expense) and interest expense were 0.05% and 0.03%, respectively.

[67] The Fund's performance during 2001 was positively affected by approximately 7.50% as a result of the Fund's receipt of proceeds from litigation settlements relating to securities held by the Fund during prior periods and accounted for by the Fund during 2001.

[68] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were approximately 0.39% and less than 0.01%, respectively.

[69] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This expense limitation will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[70] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.67% and 0.05%, respectively.

[71] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.61% and 0.02%, respectively.

[72] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.52% and 0.06%, respectively.

[73] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees) and indirect transaction fees were 0.50% and 0.03%, respectively.

[74] The Fund commenced operations on June 28, 1996 with two classes of shares - Class I shares and Class II shares. No Class II shares were outstanding as of October 16, 1996. Class III shares were first issued on October 22, 1996. Class I shares converted to Class III shares on January 9, 1998. Class III performance information presented in the table represents Class II performance from June 28, 1996 to October 16, 1996, Class I performance from October 16, 1996 to October 21, 1996, and Class III performance thereafter. The performance information (before and after taxes) for all periods prior to June 30, 2002 was achieved prior to the change in the Fund's principal investment strategies, effective June 30, 2002.

[75] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.48%, less than 0.01%, and 0.05%, respectively.

[76] Subject to certain exclusions ("Excluded Fund Fees and Expenses"), Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.00% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. This contractual expense limitation continues through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[77] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.49%, less than 0.01%, and 0.05%, respectively.

[78] The Fund's Board of Trustees has approved amendments to the Fund's management agreement and shareholder servicing agreement pursuant to which the Fund would pay the Manager an investment management fee equal to 0.65% of the average daily net assets and a shareholder service fee of 0.15% with respect to the Fund's Class III shares. The Fund currently pays no management or shareholder service fees directly to the Manager, but bears indirectly the management and shareholder service fees charged by the underlying Funds (defined below) in which the Fund invests. Under this new fee arrangement, the Manager would agree to reduce its management and shareholder service fees from the Fund by an amount equal to the management and shareholder service fees received by the Manager from the underlying Funds in respect of the Fund's investments. The new fee arrangements will go into effect only if the amended management agreement is approved by the Fund's shareholders.

[79] The amount has been restated to reflect current fees of certain underlying funds. These indirect expenses include interest expense that may be incurred by certain underlying funds and also include, to the extent applicable, purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of interest expense and transaction fees and as restated), indirect interest expense, and indirect transaction fees were approximately 0.51%, less than 0.01%, and 0.06%, respectively.

[80] Grantham, Mayo, Van Otterloo & Co. LLC (the "Manager" or "GMO") has contractually agreed through at least June 30, 2012 to waive the Fund's shareholder service fee to the extent that the aggregate of any direct and indirect shareholder service fees borne by a class of shares of the Fund exceeds the applicable shareholder service fee set forth in the table above; provided, however, that the amount of this waiver will not exceed the applicable shareholder service fee set forth in the table above. In addition, subject to certain exclusions ("Excluded Fund Fees and Expenses"), the Manager has contractually agreed to reimburse the Fund to the extent the Fund's total annual operating expenses exceed 0.50% of the Fund's average daily net assets. Excluded Fund Fees and Expenses include shareholder service fees, underlying fund expenses, independent Trustee expenses, certain legal costs, investment-related costs (e.g., brokerage commissions and securities lending fees), extraordinary expenses, and other expenses described under "Expense Reimbursement" in this Prospectus. The Manager also has contractually agreed to reimburse the Fund for the amount of fees and expenses incurred indirectly by the Fund through its investment in other Funds of GMO Trust (excluding those Funds' Excluded Fund Fees and Expenses), subject to a maximum total reimbursement to the Fund of such fees and expenses equal to 0.50% of the Fund's average daily net assets. These expense limitations will continue through at least June 30, 2012, and may not be terminated prior to this date without the consent of the Fund's Board of Trustees.

[81] The amounts have been restated to reflect current fees of certain underlying funds. These indirect expenses include, to the extent applicable, commission fees and purchase premiums and redemption fees ("transaction fees") charged by certain underlying funds. Net fees and expenses of underlying funds (before addition of transaction fees and as restated) and indirect transaction fees were 0.43% and 0.01%, respectively.