485BPOS

As filed with the Securities and Exchange Commission on September 1, 2011

Securities Act Registration No. 2-34223

Investment Company Act File No. 811-1829

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-1A

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Post-Effective Amendment No. 92

and

REGISTRATION STATEMENT

UNDER

THE INVESTMENT COMPANY ACT OF 1940

Amendment No. 67

COLUMBIA ACORN TRUST

227 West Monroe Street, Suite 3000

Chicago, Illinois 60606

Telephone number: 312.634.9200

Charles P. McQuaid Columbia Acorn Trust 227 West Monroe Street, Suite 3000 Chicago, Illinois 60606	Scott R. Plummer c/o Columbia Management Investment Advisers, LLC 225 Franklin Street Boston, MA 02110	Mary C. Moynihan Perkins Coie LLP 700 13th Street, N.W., Suite 600 Washington, D.C. 20005
(Agents for service)

It is proposed that this filing will become effective:

x immediately upon filing pursuant to rule 485(b)

¨ on                      pursuant to rule 485(b)

¨ 60 days after filing pursuant to rule 485(a)(1)

¨ on                      pursuant to rule 485(a)(l)

¨ 75 days after filing pursuant to rule 485(a)(2)

¨ on                      pursuant to rule 485(a)(2).

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933 and the Investment Company Act of 1940, the Registrant certifies that it meets all the requirements for effectiveness of this post-effective amendment pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Chicago and State of Illinois on this 1^st day of September, 2011.

COLUMBIA ACORN TRUST
By	/S/    CHARLES P. MCQUAID
	Charles P. McQuaid, President

Pursuant to the requirements of the Securities Act of 1933, this amendment to the registration statement has been signed below by the following persons in the capacities and on the dates indicated.

Name	Title		Date
/S/    LAURA M. BORN	Trustee and Chair	)
Laura M. Born		)
		)
/S/    MICHELLE L. COLLINS	Trustee	)
Michelle L. Collins		)
		)
/S/    MAUREEN M. CULHANE	Trustee	)
Maureen M. Culhane		)
		)
/S/    MARGARET M. EISEN	Trustee	)
Margaret M. Eisen		)
		)
/S/    JOHN C. HEATON	Trustee	)
John C. Heaton		)
		)
/S/    STEVEN N. KAPLAN	Trustee	)
Steven N. Kaplan		)
		)
/S/    ALLAN B. MUCHIN	Trustee	)	September 1, 2011
Allan B. Muchin		)
		)
/S/    DAVID B. SMALL	Trustee	)
David B. Small		)
		)
/S/    DAVID J. RUDIS	Trustee	)
David J. Rudis		)
		)
/S/    CHARLES P. MCQUAID	Trustee and President (principal executive	)
Charles P. McQuaid	officer)	)
		)
/S/    BRUCE H. LAUER	Treasurer (principal financial and	)
Bruce H. Lauer	accounting officer)	)

Index of Exhibits Filed with this Amendment

Exhibit No.	Description
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

XML



(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes 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 (Columbia Acorn European Fund)	Class Z Shares (Columbia Acorn European Fund - Class Z)
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none

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

Annual Fund Operating Expenses (Columbia Acorn European Fund)		Class Z Shares (Columbia Acorn European Fund - Class Z)
Management fees		1.19%
Distribution and/or service (Rule 12b-1) fees		none
Other expenses	[1]	0.32%
Total annual Fund operating expenses		1.51%
Fee waivers and/or reimbursements	[2]	(0.01%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.50%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn European Fund) (USD $)	1 Year	3 Years
Class Z Shares (Columbia Acorn European Fund - Class Z)	153	476

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rate of 1.50% of the Fund's average daily net assets attributable to Class Z, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of the recoupment, whichever is less. This expense arrangement m ay only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

XML



(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Columbia Acorn Emerging Markets Fund Classes A, C & I) (Columbia Acorn Emerging Markets Fund)	Class A Shares		Class C Shares		Class I Shares
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]	1.00%	[2]

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

Annual Fund Operating Expenses (Columbia Acorn Emerging Markets Fund Classes A, C & I) (Columbia Acorn Emerging Markets Fund)		Class A Shares	Class C Shares	Class I Shares
Management fees		1.25%	1.25%	1.25%
Distribution and/or service (Rule 12b-1) fees		0.25%	1.00%	none
Other expenses	[1]	0.46%	0.48%	0.27%
Total annual Fund operating expenses		1.96%	2.73%	1.52%
Fee waivers and/or reimbursements	[2]	(0.11%)	(0.13%)	(0.11%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.85%	2.60%	1.41%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn Emerging Markets Fund) (Columbia Acorn Emerging Markets Fund Classes A, C & I) (USD $)	1 Year	3 Years
Class A Shares	752	1,145
Class C Shares	363	835
Class I Shares	144	470

Expense Example, No Redemption (Columbia Acorn Emerging Markets Fund) (USD $)	1 Year	3 Years
Class C Shares (Columbia Acorn Emerging Markets Fund Classes A, C & I)	263	835

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

[1] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[2] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.85%, 2.60% and 1.41% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

XML



(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Columbia Acorn European Fund - Classes A, C & I) (Columbia Acorn European Fund)	Class A Shares		Class C Shares		Class I Shares
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]	1.00%	[2]

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

Annual Fund Operating Expenses (Columbia Acorn European Fund - Classes A, C & I) (Columbia Acorn European Fund)		Class A Shares	Class C Shares	Class I Shares
Management fees		1.19%	1.19%	1.19%
Distribution and/or service (Rule 12b-1) fees		0.25%	1.00%	none
Other expenses	[1]	0.45%	0.47%	0.26%
Total annual Fund operating expenses		1.89%	2.66%	1.45%
Fee waivers and/or reimbursements	[2]	(0.14%)	(0.16%)	(0.14%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.75%	2.50%	1.31%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn European Fund) (Columbia Acorn European Fund - Classes A, C & I) (USD $)	1 Year	3 Years
Class A Shares	743	1,122
Class C Shares	353	811
Class I Shares	133	445

Expense Example, No Redemption (Columbia Acorn European Fund) (USD $)	1 Year	3 Years
Class C Shares (Columbia Acorn European Fund - Classes A, C & I)	253	811

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes 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 (Columbia Acorn European Fund)	Class Z Shares (Columbia Acorn European Fund - Class Z)
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none

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

Annual Fund Operating Expenses (Columbia Acorn European Fund)		Class Z Shares (Columbia Acorn European Fund - Class Z)
Management fees		1.19%
Distribution and/or service (Rule 12b-1) fees		none
Other expenses	[1]	0.32%
Total annual Fund operating expenses		1.51%
Fee waivers and/or reimbursements	[2]	(0.01%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.50%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn European Fund) (USD $)	1 Year	3 Years
Class Z Shares (Columbia Acorn European Fund - Class Z)	153	476

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Columbia Acorn Emerging Markets Fund Classes A, C & I) (Columbia Acorn Emerging Markets Fund)	Class A Shares		Class C Shares		Class I Shares
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]	1.00%	[2]

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

Annual Fund Operating Expenses (Columbia Acorn Emerging Markets Fund Classes A, C & I) (Columbia Acorn Emerging Markets Fund)		Class A Shares	Class C Shares	Class I Shares
Management fees		1.25%	1.25%	1.25%
Distribution and/or service (Rule 12b-1) fees		0.25%	1.00%	none
Other expenses	[1]	0.46%	0.48%	0.27%
Total annual Fund operating expenses		1.96%	2.73%	1.52%
Fee waivers and/or reimbursements	[2]	(0.11%)	(0.13%)	(0.11%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.85%	2.60%	1.41%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn Emerging Markets Fund) (Columbia Acorn Emerging Markets Fund Classes A, C & I) (USD $)	1 Year	3 Years
Class A Shares	752	1,145
Class C Shares	363	835
Class I Shares	144	470

Expense Example, No Redemption (Columbia Acorn Emerging Markets Fund) (USD $)	1 Year	3 Years
Class C Shares (Columbia Acorn Emerging Markets Fund Classes A, C & I)	263	835

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes 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 (Columbia Acorn Emerging Markets Fund)	Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none

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

Annual Fund Operating Expenses (Columbia Acorn Emerging Markets Fund)		Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)
Management fees		1.25%
Distribution and/or service (Rule 12b-1) fees		none
Other expenses	[1]	0.33%
Total annual Fund operating expenses		1.58%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn Emerging Markets Fund) (USD $)	1 Year	3 Years
Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)	161	499

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

[1] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[2] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.75%, 2.50% and 1.31% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rate of 1.50% of the Fund's average daily net assets attributable to Class Z, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of the recoupment, whichever is less. This expense arrangement m ay only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[1] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[2] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.85%, 2.60% and 1.41% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[1] Other expenses are based on estimated amounts for the current fiscal year.

XML



Shareholder Fees	0 Months Ended
	Aug. 19, 2011
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class A Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class C Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[2]
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class I Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value
(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund) | Class Z Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class A Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class C Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[2]
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class I Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value
(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund) | Class Z Shares
Shareholder Fees:
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none

[1] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[2] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

XML



Annual Fund Operating Expenses	0 Months Ended
	Aug. 19, 2011
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class A Shares
Operating Expenses:
Management fees	1.19%
Distribution and/or service (Rule 12b-1) fees	0.25%
Other expenses	0.45%	[1]
Total annual Fund operating expenses	1.89%
Fee waivers and/or reimbursements	(0.14%)	[2]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	1.75%
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class C Shares
Operating Expenses:
Management fees	1.19%
Distribution and/or service (Rule 12b-1) fees	1.00%
Other expenses	0.47%	[1]
Total annual Fund operating expenses	2.66%
Fee waivers and/or reimbursements	(0.16%)	[2]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	2.50%
(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class I Shares
Operating Expenses:
Management fees	1.19%
Distribution and/or service (Rule 12b-1) fees	none
Other expenses	0.26%	[1]
Total annual Fund operating expenses	1.45%
Fee waivers and/or reimbursements	(0.14%)	[2]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	1.31%
(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund) | Class Z Shares
Operating Expenses:
Management fees	1.19%
Distribution and/or service (Rule 12b-1) fees	none
Other expenses	0.32%	[1]
Total annual Fund operating expenses	1.51%
Fee waivers and/or reimbursements	(0.01%)	[3]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	1.50%
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class A Shares
Operating Expenses:
Management fees	1.25%
Distribution and/or service (Rule 12b-1) fees	0.25%
Other expenses	0.46%	[1]
Total annual Fund operating expenses	1.96%
Fee waivers and/or reimbursements	(0.11%)	[4]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	1.85%
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class C Shares
Operating Expenses:
Management fees	1.25%
Distribution and/or service (Rule 12b-1) fees	1.00%
Other expenses	0.48%	[1]
Total annual Fund operating expenses	2.73%
Fee waivers and/or reimbursements	(0.13%)	[4]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	2.60%
(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class I Shares
Operating Expenses:
Management fees	1.25%
Distribution and/or service (Rule 12b-1) fees	none
Other expenses	0.27%	[1]
Total annual Fund operating expenses	1.52%
Fee waivers and/or reimbursements	(0.11%)	[4]
Total annual Fund operating expenses after the fee waivers and/or reimbursements	1.41%
(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund) | Class Z Shares
Operating Expenses:
Management fees	1.25%
Distribution and/or service (Rule 12b-1) fees	none
Other expenses	0.33%	[1]
Total annual Fund operating expenses	1.58%

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.75%, 2.50% and 1.31% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[3] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rate of 1.50% of the Fund's average daily net assets attributable to Class Z, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of the recoupment, whichever is less. This expense arrangement m ay only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[4] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.85%, 2.60% and 1.41% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

XML



(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes 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 (Columbia Acorn Emerging Markets Fund)	Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)
Maximum sales charge (load) imposed on purchases, as a % of offering price	none
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	none

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

Annual Fund Operating Expenses (Columbia Acorn Emerging Markets Fund)		Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)
Management fees		1.25%
Distribution and/or service (Rule 12b-1) fees		none
Other expenses	[1]	0.33%
Total annual Fund operating expenses		1.58%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn Emerging Markets Fund) (USD $)	1 Year	3 Years
Class Z Shares (Columbia Acorn Emerging Markets Fund - Class Z)	161	499

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

[1] Other expenses are based on estimated amounts for the current fiscal year.

XML



Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Document Type

dei_DocumentType

485BPOS

Document Period End Date

dei_DocumentPeriodEndDate

Aug. 19, 2011

Registrant Name

dei_EntityRegistrantName

COLUMBIA ACORN TRUST

Central Index Key

dei_EntityCentralIndexKey

0000002110

Amendment Flag

dei_AmendmentFlag

false

Document Creation Date

dei_DocumentCreationDate

Aug. 17, 2011

Document Effective Date

dei_DocumentEffectiveDate

Aug. 17, 2011

Prospectus Date

rr_ProspectusDate

Aug. 19, 2011

(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund)

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

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)

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 (or "turns over" its portfolio). 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.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example Closing [Text Block]

rr_ExpenseExampleClosingTextBlock

Remember this is an example only. Your actual costs may be higher or lower.

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 any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800.345.6611

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com

(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class A Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[4]

Management fees

rr_ManagementFeesOverAssets

1.19%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.45%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.89%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[2]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

1.75%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

743

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,122

(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class C Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[6]

Management fees

rr_ManagementFeesOverAssets

1.19%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.47%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.66%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.16%)

^[2]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

2.50%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

353

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

811

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

253

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

811

(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund) | Class I Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

Management fees

rr_ManagementFeesOverAssets

1.19%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.26%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.45%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.14%)

^[2]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

1.31%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

133

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

445

(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund)

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

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

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

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)

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 (or "turns over" its portfolio). 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.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example Closing [Text Block]

rr_ExpenseExampleClosingTextBlock

Remember this is an example only. Your actual costs may be higher or lower.

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 any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800.345.6611

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com

(Columbia Acorn European Fund - Class Z) | (Columbia Acorn European Fund) | Class Z Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

none

Management fees

rr_ManagementFeesOverAssets

1.19%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.32%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.51%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.01%)

^[1]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

1.50%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

153

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

476

(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund)

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

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)

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 (or "turns over" its portfolio). 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.

Expense Breakpoint Discounts [Text]

rr_ExpenseBreakpointDiscounts

You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds.

Expense Breakpoint, Minimum Investment Required [Amount]

rr_ExpenseBreakpointMinimumInvestmentRequiredAmount

50,000

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example Closing [Text Block]

rr_ExpenseExampleClosingTextBlock

Remember this is an example only. Your actual costs may be higher or lower.

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 any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800.345.6611

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com

(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class A Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

5.75%

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[4]

Management fees

rr_ManagementFeesOverAssets

1.25%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

0.25%

Other expenses

rr_OtherExpensesOverAssets

0.46%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.96%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[3]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

1.85%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

752

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

1,145

(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class C Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

1.00%

^[6]

Management fees

rr_ManagementFeesOverAssets

1.25%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

1.00%

Other expenses

rr_OtherExpensesOverAssets

0.48%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

2.73%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.13%)

^[3]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

2.60%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

363

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

835

Expense Example, No Redemption, 1 Year

rr_ExpenseExampleNoRedemptionYear01

263

Expense Example, No Redemption, 3 Years

rr_ExpenseExampleNoRedemptionYear03

835

(Columbia Acorn Emerging Markets Fund Classes A, C & I) | (Columbia Acorn Emerging Markets Fund) | Class I Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

Management fees

rr_ManagementFeesOverAssets

1.25%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.27%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.52%

Fee waivers and/or reimbursements

rr_FeeWaiverOrReimbursementOverAssets

(0.11%)

^[3]

Total annual Fund operating expenses after the fee waivers and/or reimbursements

rr_NetExpensesOverAssets

1.41%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

144

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

470

(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund)

Risk/Return:

rr_RiskReturnAbstract

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

The Fund seeks long-term capital appreciation.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses of the Fund

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

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

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Shareholder Fees (fees paid directly from your investment)

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)

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 (or "turns over" its portfolio). 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.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class Z shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

Based on the assumptions listed above, your costs would be:

Expense Example Closing [Text Block]

rr_ExpenseExampleClosingTextBlock

Remember this is an example only. Your actual costs may be higher or lower.

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 any borrowing for investment purposes) in companies located in emerging market countries, including frontier market countries. Emerging market countries are those countries whose economies are developing or emerging from underdevelopment (for example, China, India, Poland and Turkey). Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries (for example, Vietnam, Colombia, Nigeria and Kazakhstan). For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, an emerging market country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in an emerging market country or countries or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion. Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, wh ich generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

Generally, the Adviser will determine which countries are emerging market countries by reference to the countries included in the S&P Emerging Markets Broad Market Index (BMI), and will determine which countries are frontier market countries by reference to the countries included in the S&P Frontier BMI. In addition, the Fund may invest in certain developing market countries that are not included in either the S&P Emerging Markets BMI or the S&P Frontier BMI (for example, Iceland and Senegal), but which are included on another independent third-party listing of emerging market and/or frontier market countries. The Adviser will make all determinations as to whether a company is an emerging market company at the time of investment. The countries that comprise emerging market countries, including frontier market countries, may change from time to time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Frontier Market Risk -- Frontier market countries generally have smaller economies and even less developed capital markets than traditional emerging market countries and, as a result, the risks of investing in emerging market countries are magnified in frontier market countries. The magnification of risks are the result of: potential for extreme price volatility and illiquidity in frontier market countries; government ownership or control of parts of private sector and of certain companies; trade barriers, exchange controls, managed adjustments in relative currency values and other protectionist measures imposed or negotiated by the countries with which frontier market countries trade; and the relatively new and unsettled securities laws in many frontier market countries.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance Information

Performance Narrative [Text Block]

rr_PerformanceNarrativeTextBlock

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

Performance Availability Phone [Text]

rr_PerformanceAvailabilityPhone

800.345.6611

Performance Availability Website Address [Text]

rr_PerformanceAvailabilityWebSiteAddress

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com

(Columbia Acorn Emerging Markets Fund - Class Z) | (Columbia Acorn Emerging Markets Fund) | Class Z Shares

Risk/Return:

rr_RiskReturnAbstract

Maximum sales charge (load) imposed on purchases, as a % of offering price

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value

rr_MaximumDeferredSalesChargeOverOther

none

Management fees

rr_ManagementFeesOverAssets

1.25%

Distribution and/or service (Rule 12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.33%

^[5]

Total annual Fund operating expenses

rr_ExpensesOverAssets

1.58%

Expense Example, with Redemption, 1 Year

rr_ExpenseExampleYear01

161

Expense Example, with Redemption, 3 Years

rr_ExpenseExampleYear03

499

[1] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rate of 1.50% of the Fund's average daily net assets attributable to Class Z, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of the recoupment, whichever is less. This expense arrangement m ay only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.75%, 2.50% and 1.31% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[3] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.85%, 2.60% and 1.41% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.

[4] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[5] Other expenses are based on estimated amounts for the current fiscal year.

[6] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

XML



(Columbia Acorn European Fund - Classes A, C & I) | (Columbia Acorn European Fund)

Investment Objective

The Fund seeks long-term capital appreciation.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in Class A shares of eligible Columbia funds within the Columbia family of mutual funds. More information about these and other discounts is available from your financial advisor, in the Choosing a Share Class section beginning on page 17 of this prospectus and in Appendix D to the Statement of Additional Information under Sales Charge Waivers beginning on page D-1.

Shareholder Fees (fees paid directly from your investment)

Shareholder Fees (Columbia Acorn European Fund - Classes A, C & I) (Columbia Acorn European Fund)	Class A Shares		Class C Shares		Class I Shares
Maximum sales charge (load) imposed on purchases, as a % of offering price	5.75%
Maximum deferred sales charge (load) imposed on redemptions, as a % of the lower of the original purchase price or net asset value	1.00%	[1]	1.00%	[2]

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

Annual Fund Operating Expenses (Columbia Acorn European Fund - Classes A, C & I) (Columbia Acorn European Fund)		Class A Shares	Class C Shares	Class I Shares
Management fees		1.19%	1.19%	1.19%
Distribution and/or service (Rule 12b-1) fees		0.25%	1.00%	none
Other expenses	[1]	0.45%	0.47%	0.26%
Total annual Fund operating expenses		1.89%	2.66%	1.45%
Fee waivers and/or reimbursements	[2]	(0.14%)	(0.16%)	(0.14%)
Total annual Fund operating expenses after the fee waivers and/or reimbursements		1.75%	2.50%	1.31%

Example

The following 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 illustrates the hypothetical expenses that you would incur over the time periods indicated, and assumes that:

• you invest $10,000 in Class A, Class C or Class I shares of the Fund for the periods indicated,

• your investment has a 5% return each year, and

• the Fund's total annual operating expenses remain the same as shown in the table above.

The waivers and/or reimbursements shown in the Annual Fund Operating Expenses table above expire on April 30, 2013 and are only reflected in the 1 year example and the first year of the 3 year example.

Based on the assumptions listed above, your costs would be:

Expense Example (Columbia Acorn European Fund) (Columbia Acorn European Fund - Classes A, C & I) (USD $)	1 Year	3 Years
Class A Shares	743	1,122
Class C Shares	353	811
Class I Shares	133	445

Expense Example, No Redemption (Columbia Acorn European Fund) (USD $)	1 Year	3 Years
Class C Shares (Columbia Acorn European Fund - Classes A, C & I)	253	811

Remember this is an example only. Your actual costs may be higher or lower.

Portfolio Turnover

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or "turns over" its portfolio). 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.

Principal Investment Strategies

Under normal circumstances, the Fund invests at least 80% of its net assets (plus any borrowing for investment purposes) in European companies. Under normal circumstances, the Fund invests at least 70% of its total assets in companies in Western European countries (for example, the United Kingdom, Germany, France and Italy), but also may invest up to 30% of its total assets in companies in emerging Central and Eastern European countries (for example, Poland, the Czech Republic, Turkey and Cyprus), including up to 10% of its total assets in companies in Russia and the Ukraine. For purposes of the Fund's policies, the Fund may invest in a company if (i) it is domiciled in, or the principal trading market for its securities is in, a European country, (ii) it derives 50% or more of its economic value from goods produced, sales made or services performed or has at least 50% of its assets in a European country or (iii) it is a holding company that predominantly holds shares in such companies. The Fund may invest in a variety of countries, industries and sectors and does not attempt to invest a specific percentage of its assets in any given country, industry or sector.

Under normal circumstances, the Fund invests a majority of its net assets in the common stock of small- and mid-sized companies with market capitalizations under $5 billion at the time of investment. However, if the Fund's investments in such companies represent less than a majority of its net assets, the Fund may continue to hold and to make additional investments in an existing company in its portfolio even if that company's capitalization has grown to exceed $5 billion. Except as noted above, under normal circumstances, the Fund may invest in other companies with market capitalizations above $5 billion, provided that immediately after that investment a majority of its net assets would be invested in companies with market capitalizations under $5 billion.

Columbia Wanger Asset Management, LLC, the Fund's investment adviser (the Adviser), believes that stocks of companies with market capitalizations under $5 billion, which generally are not as well known by financial analysts as larger companies, may offer higher return potential than stocks of larger companies.

The Fund takes advantage of the Adviser's research and stock-picking capabilities to initially invest in a limited number of companies (generally under 100), offering the potential to provide above-average growth over time.

The Adviser typically seeks companies with:

• A strong business franchise that offers growth potential.

• Products and services that give the company a competitive advantage.

• A stock price the Adviser believes is reasonable relative to the assets and earning power of the company.

The Adviser may sell a portfolio holding if the security reaches the Adviser's price target, if the company has a deterioration of fundamentals, such as failing to meet key operating benchmarks, or if the Adviser believes other securities are more attractive. The Adviser also may sell a portfolio holding to fund redemptions.

Principal Risks

• Investment Strategy Risk -- The Adviser uses the principal investment strategies and other investment strategies to seek to achieve the Fund's investment objective. There is no assurance that the Fund will achieve its investment objective. Investment decisions made by the Adviser in using these strategies may not produce the returns expected by the Adviser, may cause the Fund's shares to lose value or may cause the Fund to underperform other funds with similar investment objectives.

• Market Risk -- Market risk refers to the possibility that the market values of securities that the Fund holds will fall, sometimes rapidly or unpredictably. Security values may fall because of factors affecting individual companies, industries or sectors, or the markets as a whole, reducing the value of an investment in the Fund. Accordingly, an investment in the Fund could lose money over short or even long periods. The market values of the securities the Fund holds also can be affected by changes or perceived changes in U.S. or foreign economies and financial markets, and the liquidity of these securities, among other factors. In general, equity securities tend to have greater price volatility than debt securities.

• Foreign Securities Risk -- Foreign securities are subject to special risks as compared to securities of U.S. issuers. For example, foreign markets can be extremely volatile. Fluctuations in currency exchange rates may impact the value of foreign securities denominated in foreign currencies or in U.S. dollars, without a change in the intrinsic value of those securities. Foreign securities may be less liquid than domestic securities so that the Fund may, at times, be unable to sell foreign securities at desirable times or prices. Brokerage commissions, custodial fees and other fees are also generally higher for foreign securities. The Fund may have limited or no legal recourse in the event of default with respect to certain foreign securities, including those issued by foreign governments. In addition, foreign governments may impose potentially confiscatory withholding or other taxes, which could reduce the amount of income and capital gains available to distribute to s hareholders. Other risks include possible delays in the settlement of transactions or in the payment of income; generally less publicly available information about companies; the impact of political, social or diplomatic events; possible seizure, expropriation or nationalization of a company or its assets; possible imposition of currency exchange controls; and accounting, auditing and financial reporting standards that may be less comprehensive and stringent than those applicable to domestic companies.

• Emerging Market Securities Risk -- Securities issued by foreign governments or companies in emerging market countries, like those in Eastern Europe, the Middle East, Asia, Latin America or Africa, are more likely to have greater exposure to the risks of investing in foreign securities that are described in Foreign Securities Risk. In addition, emerging market countries are more likely to experience instability resulting, for example, from rapid social, political and economic development. Their economies are usually less mature and their securities markets are typically less developed with more limited trading activity than more developed countries. Emerging market securities tend to be more volatile than securities in more developed markets. Many emerging market countries are heavily dependent on international trade, which makes them more sensitive to world commodity prices and economic downturns in other countries. Some emerging market countries have a higher risk of currency de valuations, and some of these countries may experience periods of high inflation or rapid changes in inflation rates.

• Smaller Company Securities Risk -- Securities of small- or mid-capitalization companies ("smaller companies") can, in certain circumstances, have a higher potential for gains than securities of large-capitalization companies but may also have more risk. For example, smaller companies may be more vulnerable to market downturns and adverse business or economic events than larger, more established companies because they may have more limited financial resources and business operations. These companies are also more likely than large-capitalization companies ("larger companies") to have more limited product lines and operating histories and to depend on smaller management teams. Their securities may trade less frequently and in smaller volumes and may be less liquid and fluctuate more sharply in value than securities of larger companies. In cases where the Fund takes significant positions in smaller companies with limited trading volumes, the liquidation of those position s, particularly in a distressed market, could be prolonged and result in investment losses. In addition, some smaller companies may not be widely followed by the investment community, which can lower the demand for their stocks.

• Currency Risk -- Securities denominated in different currencies are subject to the risk that, for example, if the value of a foreign currency were to decline against the U.S. dollar, such decline would reduce the U.S. dollar value of any securities held by the Fund denominated in that currency.

• Sector Risk -- At times, the Fund may have a significant portion of its assets invested in securities of companies conducting business in a broadly related group of industries within an economic sector. Companies in the same economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments in that economic sector than funds that invest more broadly.

• Special Situations Risk -- Securities of companies that are involved in an initial public offering or a major corporate event, such as a business consolidation or restructuring, may present special risk because of the high degree of uncertainty that can be associated with such events. Securities issued in initial public offerings often are issued by companies that are in the early stages of development, have a history of little or no revenues and may operate at a loss following the offering. It is possible that there will be no active trading market for the securities after the offering, and that the market price of the securities may be subject to significant and unpredictable fluctuations. Investing in special situations may have a magnified effect on the performance of funds with small amounts of assets.

Performance Information

Because the Fund commenced investment operations on or about August 19, 2011, no year-by-year total return bar chart or average annual total return table is being presented. The year-by year-total return bar chart and the average annual total return table will be provided after the Fund has annual returns for at least one calendar year.

More recent performance information will be available on the Columbia Funds' website at www.columbiamanagement.com or by calling 800.345.6611.

[1] Contingent deferred sales charges (CDSC) on certain investments of between $1 million and $50 million redeemed within 18 months of purchase, charged as follows: 1.00% CDSC if redeemed within 12 months of purchase, and 0.50% CDSC if redeemed more than 12, but less than 18, months of purchase, with certain limited exceptions.

[2] This charge applies to investors who buy Class C shares and redeem them within one year of purchase, with certain limited exceptions.

[1] Other expenses are based on estimated amounts for the current fiscal year.

[2] Columbia Wanger Asset Management, LLC (the Adviser) has contractually agreed to waive fees and reimburse certain expenses of the Fund so that the ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) do not exceed the annual rates of 1.75%, 2.50% and 1.31% of the Fund's average daily net assets attributable to Class A, Class C and Class I shares, respectively, through April 30, 2013. The Adviser may recoup any fees waived and/or expenses reimbursed with respect to any share class of the Fund for a one-year period following the date of such fee waiver and/or reimbursement if such recovery does not cause the Fund's ordinary operating expenses (excluding interest and fees on borrowings and expenses associated with the Fund's investment in other investment companies, if any) to exceed the annual rates set forth in this prospectus, or to exceed such annual rate as may be in place at the time of t he recoupment, whichever is less. This expense arrangement may only be modified or amended with approval from all parties to such arrangements, including the Fund and the Adviser.