Item 1: Report to Shareholders

 GNMA Fund May 31, 2006 

The views and opinions in this report were current as of May 31, 2006. They are not guarantees of performance or investment results and should not be taken as investment advice. Investment decisions reflect a variety of factors, and the managers reserve the right to change their views about individual stocks, sectors, and the markets at any time. As a result, the views expressed should not be relied upon as a forecast of the fund’s future investment intent. The report is certified under the Sarbanes-Oxley Act of 2002, which requires mutual funds and other public companies to affirm that, to the best of their knowledge, the information in their financial reports is fairly and accurately stated in all material respects.

REPORTS ON THE WEB

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Fellow Shareholders

Thanks to strong demand, mortgages provided better returns than the bond market as a whole over the past six months, returning 58 basis points (0.58%) more than equal-duration Treasuries. GNMA mortgages did not fare as well, however, outpacing equal-duration Treasuries by only 30 basis points. Over the past 12 months, GNMAs underperformed Treasuries by 24 basis points as the mortgage sector suffered from volatility in the first half of our fiscal year. Your fund posted a modest gain for the year, reflecting this challenging environment.

MARKET ENVIRONMENT

Bond markets struggled since our last report as investors worried how the continuing economic expansion and high energy prices might affect inflation and Fed policy. While the housing sector cooled, with inventories of unsold homes rising and price gains moderating, little evidence suggested that the weakness was spreading to the rest of the economy. Indeed, the government announced that the economy had recovered from its slowdown following the hurricanes in late 2005 and had grown at an annualized rate of 5.3% in the first quarter of 2006, its fastest pace in nearly two years. The job market remained generally strong, with the unemployment rate falling to 4.6% in May.

With the economic expansion on solid footing, the Federal Reserve remained resolutely on its path of monetary tightening. The Fed’s monetary policy committee continued raising official short-term interest rates by a quarter point at every meeting, bringing the federal funds target rate to 5%, its highest level in five years. Having proved surprisingly stubborn last year, longer-term interest rates generally moved higher alongside short-term rates during the past six months—although to a lesser degree. Minutes of their last meeting held during our reporting period indicated that Fed officials worried inflationary pressures could worsen, which suggested they would feel constrained to send rates higher still.

PERFORMANCE AND STRATEGY REVIEW

The GNMA Fund returned 0.29% for the six-month period ended May 31, 2006, and 0.32% for the fiscal year. As shown in the table, the portfolio outperformed its peer group of funds as represented by the Lipper GNMA Funds Average, while lagging the Lehman Brothers and Citigroup GNMA Indexes. (In future reports, we will replace comparisons to the Citigroup GNMA Index with an evaluation of returns relative to the Lehman Brothers U.S. GNMA Index, a more commonly recognized benchmark that we are introducing in this letter.) The fund’s net asset value (NAV) fell by $0.20 over the past six months, but this was more than offset by $0.23 in dividends paid out over the period; over the 12-month period, the fund’s NAV fell by $0.42, which was offset by $0.45 in dividends.

Returns for GNMAs in recent years have been driven by two major forces. First, supply of GNMAs has been decreasing for the last several years. As a result, GNMAs currently represent only 3.7% of the Lehman Brothers U.S. Aggregate Index versus over 8% a decade ago. The second force driving GNMA returns, demand from foreign central banks, has recently waned somewhat. In past years, foreign banks have focused their buying in the mortgage market on GNMAs because they are backed by the full faith and credit of the U.S. government. Foreign buying resulted in tremendous outperformance by GNMAs in 2005, helping them return 3.20% for the year versus 2.61% for the mortgage sector overall (as measured by Lehman Brothers GNMA and MBS indexes, respectively). However, foreign demand so far in 2006 has been much lower than anticipated, and returns for GNMAs have weakened as a result.

Our strategy over most of the period was to keep the portfolio’s duration slightly shorter than the Lehman GNMA benchmark; in other words, our maturity posture was somewhat less sensitive to rising interest rates. We accomplished this by owning more 15-year mortgages than the Lehman index and by shorting Treasury futures—a strategy that achieved the same results as selling Treasury securities. Since GNMAs provided some excess returns over Treasuries, and since interest rates rose significantly, this positioning paid off. Going forward, our stance on interest rates is less defensive given that the Federal Reserve appears to be close to finishing the current tightening cycle. We have raised the portfolio’s duration to neutral relative to the Lehman benchmark, and we will consider adopting a slightly longer-than-average duration as we perceive the cycle to be ending.

A NOTE ON OUR RECENT PROXY VOTE

We want to thank all of our shareholders for participating in our recent proxy. As most of you know, we sought to change the investment guidelines to allow the GNMA Fund to invest up to 20% in non-GNMA, non-full-faith-and-credit securities. This change was approved with more than 80% of the votes. Our reasons for seeking this change were twofold. First, as mentioned above, GNMAs are a shrinking asset class. As such, the demand for a smaller set of securities has driven the valuations of GNMAs to what we consider “rich” levels. We find that we can implement our investment strategies using other mortgage securities, such as those issued by Fannie Mae (FNMA) and Freddie Mac (FHLMC), and get better value.

Second, by allowing the portfolio to include other types of high-quality securities, such as asset-backed securities (ABS) and commercial mortgage-backed securities (CMBS), we believe that we can improve certain characteristics of the portfolio, such as cash flow stability. These securities have often provided better yield and total return as well. While these changes allow us to invest up to 20% of the fund in securities with a quality rating below that of a government guarantee, the overall quality of the portfolio will remain quite high. Most credit analysts consider FNMA and FHLMC quality—known as “agency quality”—to be superior to a AAA rating. Our ABS and CMBS holdings will be predominantly AAA rated, with the lowest we are allowed to buy rated AA.

Our move to diversify the fund will be gradual and opportunistic. At the time of this writing, we have only swapped about 2% of the GNMAs in the portfolio into other (AAA or agency) products. We will look carefully for good value before implementing any trade, which we perform only if we believe it will enhance your returns.

Finally, let me add a note about our use of derivatives. The fund has long had the ability to use futures and certain other derivatives, and we havegenerally been very cautious in deploying them. The change in the fund’s objective and its ability to use additional derivatives, such as swaps, will not alter that approach.

OUTLOOK

The interest rate outlook, particularly for short-term securities, has become somewhat more uncertain amid indications that the Fed may stop raising official rates if the economic and inflation data are encouraging. Given the strong U.S. economy, we believe the potential exists for at least a few more increases in the federal funds rate, which would probably also mean that longer-term bond yields would continue rising modestly. We will keep a careful eye on the data ourselves and attempt to position the fund to best exploit these interest rate changes. Additionally, we will redeploy assets into the new types of securities included in our investment guidelines when we see good values and the opportunity to improve the portfolio’s risk characteristics. Our primary goal will be to maintain a high-quality portfolio that offers investors the chance to earn yields superior to Treasuries with little additional credit risk.

As always, thank you for investing with T. Rowe Price.

Respectfully submitted,

Connice A. Bavely
Chairman of the Investment Advisory Committee

June 19, 2006

The committee chairman has day-to-day responsibility for managing the portfolio and works with committee members in developing and executing the fund’s investment program.

RISK OF GNMA FUND INVESTING

Even though principal and interest payments on GNMAs are guaranteed, an increase in interest rates can cause the share price to decline, resulting in a loss of principal. Investors in bond funds are also subject to several other types of risk—interest rate risk, credit risk, prepayment risk, extension risk, and derivatives risk. Since the fund invests primarily in GNMAs, which are backed by the full faith and credit of the U.S. government, its exposure to credit risk is low. A mortgage-backed bond, unlike most other bonds, can be hurt when interest rates fall because homeowners tend to refinance and prepay principal. Prepayments can cause the average maturity of the portfolio to shorten, require the fund to reinvest proceeds at lower interest rates, or even cause certain bonds’ prices to fall below what the fund paid for them, resulting in a capital loss. Increased interest rates can cause the fund’s average maturity to lengthen unexpectedly due to a drop in mortgage prepayments. Shareholders are also exposed to derivatives risk, the potential that our investments in these complex and volatile instruments could affect the fund’s share price.

GLOSSARY

Average maturity: For a bond fund, this is the weighted average of the stated maturity dates of the portfolio’s securities. In general, the longer the average maturity, the greater the fund’s sensitivity to interest rate changes, which can mean greater price fluctuation. A shorter average maturity usually means less interest rate sensitivity and, consequently, a less volatile portfolio.

Basis point: One one-hundredth of one percentage point, or 0.01%.

Call protection: Any of a number of provisions that prohibits a bond’s early redemption for a given period.

Citigroup GNMA Index: A market value-weighted index of 15- and 30-year fixed-rate securities backed by mortgage pools of the Government National Mortgage Association (GNMA).

Collateralized mortgage obligation (CMO): Collateralized mortgage obligations are investment-grade bonds that are backed by mortgage pass-throughs whose cash flows are directed in different ways to different classes. Some classes may have less risk associated with prepayments, and, by default, the other classes will have more prepayment risk. Those classes with less risk generally yield less than other mortgage-backed securities.

Current coupon GNMA: An index that tracks a theoretical 30-year GNMA mortgage that is priced at par. It is computed by interpolating from the two 30-year GNMAs whose prices bracket par.

Duration: A measure of a bond or bond fund’s sensitivity to changes in interest rates. For example, a fund with a duration of five years would fall about 5% in response to a one-percentage-point rise in rates, and vice versa.

Extension risk: As interest rates rise, the likelihood of prepayment decreases, and the average life and duration of mortgage securities lengthens. Investors are unable to capitalize on higher interest rates because their investment is locked in at a lower rate for a longer period of time.

Implied volatility: A theoretical value designed to represent the volatility of the security underlying an option as determined by the price of the option. It is a representation of the market’s best estimate for future volatility.

Lehman Brothers MBS Index: An index that tracks the performance of the mortgage-backed pass-through securities of Ginnie Mae (GNMA), Fannie Mae (FNMA), and Freddie Mac (FHLMC).

Lehman Brothers U.S. GNMA Index: Tracks the performance of mortgage-backed pass-through securities of the Government National Mortgage Association (GNMA).

Lipper averages: Consist of all mutual funds in a particular category as tracked by Lipper Inc.

Real interest rate: The excess of the current interest rate over the current inflation rate.

Total return: The annual rate of return on a bond, taking into account interest income, plus appreciation or depreciation. If a bond is held to maturity, its total return equals its yield to maturity.

Yield curve: A graphic depiction of the relationship between yields and maturity dates for a set of similar securities, such as Treasuries or municipal securities. Securities with longer maturities usually have a higher yield. If short-term securities offer a higher yield, then the curve is said to be “inverted.” If short- and long-term bonds are offering equivalent yields, then the curve is said to be “flat.”

GROWTH OF $10,000 

This chart shows the value of a hypothetical $10,000 investment in the fund over the past 10 fiscal year periods or since inception (for funds lacking 10-year records). The result is compared with benchmarks, which may include a broad-based market index and a peer group average or index. Market indexes do not include expenses, which are deducted from fund returns as well as mutual fund averages and indexes.

AVERAGE ANNUAL COMPOUND TOTAL RETURN 

This table shows how the fund would have performed each year if its actual (or cumulative) returns for the periods shown had been earned at a constant rate.

FUND EXPENSE EXAMPLE 

As a mutual fund shareholder, you may incur two types of costs: (1) transaction costs such as redemption fees or sales loads and (2) ongoing costs, including management fees, distribution and service (12b-1) fees, and other fund expenses. The following example is intended to help you understand your ongoing costs (in dollars) of investing in the fund and to compare these costs with the ongoing costs of investing in other mutual funds. The example is based on an investment of $1,000 invested at the beginning of the most recent six-month period and held for the entire period.

Actual Expenses
The first line of the following table (“Actual”) provides information about actual account values and actual expenses. You may use the information in this line, together with your account balance, to estimate the expenses that you paid over the period. Simply divide your account value by $1,000 (for example, an $8,600 account value divided by $1,000 = 8.6), then multiply the result by the number in the first line under the heading “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Hypothetical Example for Comparison Purposes
The information on the second line of the table (“Hypothetical”) is based on hypothetical account values and expenses derived from the fund’s actual expense ratio and an assumed 5% per year rate of return before expenses (not the fund’s actual return). You may compare the ongoing costs of investing in the fund with other funds by contrasting this 5% hypothetical example and the 5% hypothetical examples that appear in the shareholder reports of the other funds. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period.

Note: T. Rowe Price charges an annual small-account maintenance fee of $10, generally for accounts with less than $2,000 ($500 for UGMA/UTMA). The fee is waived for any investor whose T. Rowe Price mutual fund accounts total $25,000 or more, accounts employing automatic investing, and IRAs and other retirement plan accounts that utilize a prototype plan sponsored by T. Rowe Price (although a separate custodial or administrative fee may apply to such accounts). This fee is not included in the accompanying table. If you are subject to the fee, keep it in mind when you are estimating the ongoing expenses of investing in the fund and when comparing the expenses of this fund with other funds.

You should also be aware that the expenses shown in the table highlight only your ongoing costs and do not reflect any transaction costs, such as redemption fees or sales loads. Therefore, the second line of the table is useful in comparing ongoing costs only and will not help you determine the relative total costs of owning different funds. To the extent a fund charges transaction costs, however, the total cost of owning that fund is higher.

The accompanying notes are an integral part of these financial statements.

The accompanying notes are an integral part of these financial statements.

The accompanying notes are an integral part of these financial statements.

The accompanying notes are an integral part of these financial statements.

The accompanying notes are an integral part of these financial statements.

NOTES TO FINANCIAL STATEMENTS 

NOTE 1 - SIGNIFICANT ACCOUNTING POLICIES

T. Rowe Price GNMA Fund (the fund) is registered under the Investment Company Act of 1940 (the 1940 Act) as a diversified, open-end management investment company. The fund commenced operations on November 26, 1985. The fund seeks high current income consistent with maximum credit protection and moderate price fluctuation by investing exclusively in securities backed by the full faith and credit of the U.S. government and instruments linked to these securities.

The accompanying financial statements were prepared in accordance with accounting principles generally accepted in the United States of America, which require the use of estimates made by fund management. Fund management believes that estimates and security valuations are appropriate; however, actual results may differ from those estimates, and the security valuations reflected in the financial statements may differ from the value the fund ultimately realizes upon sale of the securities.

Valuation The fund values its investments and computes its net asset value per share at the close of the New York Stock Exchange (NYSE), normally 4 p.m. ET, each day that the NYSE is open for business. Debt securities are generally traded in the over-the-counter market. Securities with original maturities of one year or more are valued at prices furnished by dealers who make markets in such securities or by an independent pricing service, which considers yield or price of bonds of comparable quality, coupon, maturity, and type, as well as prices quoted by dealers who make markets in such securities. Securities with original maturities of less than one year are stated at fair value, which is determined by using a matrix system that establishes a value for each security based on bid-side money market yields.

Investments in mutual funds are valued at the mutual fund’s closing net asset value per share on the day of valuation. Financial futures contracts are valued at closing settlement prices.

Other investments, including restricted securities, and those for which the above valuation procedures are inappropriate or are deemed not to reflect fair value are stated at fair value as determined in good faith by the T. Rowe Price Valuation Committee, established by the fund’s Board of Trustees.

Credits The fund earns credits on temporarily uninvested cash balances at the custodian that reduce the fund’s custody charges. Custody expense in the accompanying financial statements is presented before reduction for credits, which are reflected as expenses paid indirectly.

In-Kind Redemptions In accordance with guidelines described in the fund’s prospectus, the fund may distribute portfolio securities rather than cash as payment for a redemption of fund shares (in-kind redemption). For financial reporting purposes, the fund recognizes a gain on in-kind redemptions to the extent the value of the distributed securities on the date of redemption exceeds the cost of those securities; the fund recognizes a loss if cost exceeds value. Gains and losses realized on in-kind redemptions are not recognized for tax purposes, and are reclassified from undistributed realized gain (loss) to paid-in capital. During the year ended May 31, 2006, the fund realized $1,074,000 of net loss on $94,755,000 of in-kind redemptions.

Investment Transactions, Investment Income, and Distributions Income and expenses are recorded on the accrual basis. Premiums and discounts on debt securities are amortized for financial reporting purposes. Inflation adjustments to the principal amount of inflation-indexed bonds are reflected as interest income. Dividends received from mutual fund investments are reflected as dividend income; capital gain distributions are reflected as realized gain/loss. Dividend income and capital gain distributions are recorded on the ex-dividend date. Investment transactions are accounted for on the trade date. Realized gains and losses are reported on the identified cost basis. Payments (“variation margin”) made or received to settle the daily fluctuations in the value of futures contracts are recorded as unrealized gains or losses until the contracts are closed. Unsettled variation margin on futures contracts is reflected as other assets or liabilities, and unrealized gains and losses on futures contracts are reflected as the change in net unrealized gain or loss in the accompanying financial statements. Paydown gains and losses are recorded as an adjustment to interest income. Distributions to shareholders are recorded on the ex-dividend date. Income distributions are declared on a daily basis and paid monthly. Capital gain distributions, if any, are declared and paid by the fund, typically on an annual basis.

NOTE 2 - INVESTMENT TRANSACTIONS

Consistent with its investment objective, the fund engages in the following practices to manage exposure to certain risks or enhance performance. The investment objective, policies, program, and risk factors of the fund are described more fully in the fund’s prospectus and Statement of Additional Information.

Futures Contracts During the year ended May 31, 2006, the fund was a party to futures contracts, which provide for the future sale by one party and purchase by another of a specified amount of a specific financial instrument at an agreed upon price, date, time, and place. Risks arise from possible illiquidity of the futures market and from movements in security values and/or interest rates.

TBA Purchase Commitments During the year ended May 31, 2006, the fund entered into TBA (to be announced) purchase commitments, pursuant to which it agrees to purchase mortgage-backed securities for a fixed unit price, with payment and delivery at a scheduled future date beyond the customary settlement period for that security. With TBA transactions, the particular securities to be delivered are not identified at trade date; however, delivered securities must meet specified terms, including issuer, rate, and mortgage term, and be within industry-accepted “good delivery” standards. The fund generally enters into TBAs with the intention of taking possession of the underlying mortgage securities. Until settlement, the fund maintains cash reserves and liquid assets sufficient to settle its TBAs.

Dollar Rolls During the year ended May 31, 2006, the fund entered into dollar roll transactions, pursuant to which it sells a mortgage-backed TBA or security and simultaneously purchases a similar, but not identical, TBA with the same issuer, rate, and terms. The fund may execute a “roll” to obtain better underlying mortgage securities or to enhance returns. The fund generally enters into dollar roll transactions with the intention of taking possession of the underlying mortgage securities, but may close a contract prior to settlement or “roll” settlement to a later date if deemed in the best interest of shareholders. Actual mortgages received by the fund may be less favorable than those anticipated. The fund accounts for dollar roll transactions as purchases and sales, which has the effect of increasing its portfolio turnover rate.

Other Purchases and sales of U.S. government securities, aggregated $1,752,168,000 and $1,863,226,000, respectively, for the year ended May 31, 2006.

NOTE 3 - FEDERAL INCOME TAXES

No provision for federal income taxes is required since the fund intends to continue to qualify as a regulated investment company under Subchapter M of the Internal Revenue Code and distribute to shareholders all of its taxable income and gains. Federal income tax regulations differ from generally accepted accounting principles; therefore, distributions determined in accordance with tax regulations may differ significantly in amount or character from net investment income and realized gains for financial reporting purposes. Financial reporting records are adjusted for permanent book/tax differences to reflect tax character. Financial records are not adjusted for temporary differences.

Distributions during the year ended May 31, 2006, totaled $62,466,000 and were characterized as ordinary income for tax purposes. At May 31, 2006, the tax-basis components of net assets were as follows:

Pursuant to federal income tax regulations applicable to investment companies, the fund has elected to treat net capital losses realized between November 1 and May 31 of each year as occurring on the first day of the following tax year. Consequently, $6,572,000 of realized losses reflected in the accompanying financial statements will not be recognized for tax purposes until 2007. The fund intends to retain realized gains to the extent of available capital loss carryforwards for federal income tax purposes. As of May 31, 2006, the fund had $8,219,000 of capital loss carryforwards that expire in fiscal 2012, $4,682,000 that expire in fiscal 2013, and $7,180,000 that expire in fiscal 2014.

For the year ended May 31, 2006, the fund recorded the following permanent reclassifications to reflect tax character. Reclassifications to paid-in capital relate primarily to redemptions in kind. Reclassifications between income and gain relate primarily to the differences between book/tax amortization policies. Results of operations and net assets were not affected by these reclassifications.

At May 31, 2006, the cost of investments for federal income tax purposes was $1,282,831,000.

NOTE 4 - RELATED PARTY TRANSACTIONS

The fund is managed by T. Rowe Price Associates, Inc. (the manager or Price Associates), a wholly owned subsidiary of T. Rowe Price Group, Inc. The investment management agreement between the fund and the manager provides for an annual investment management fee, which is computed daily and paid monthly. The fee consists of an individual fund fee, equal to 0.15% of the fund’s average daily net assets, and a group fee. The group fee rate is calculated based on the combined net assets of certain mutual funds sponsored by Price Associates (the group) applied to a graduated fee schedule, with rates ranging from 0.48% for the first $1 billion of assets to 0.29% for assets in excess of $160 billion. The fund’s group fee is determined by applying the group fee rate to the fund’s average daily net assets. At May 31, 2006, the effective annual group fee rate was 0.31%.

In addition, the fund has entered into service agreements with Price Associates and two wholly owned subsidiaries of Price Associates (collectively, Price). Price Associates computes the daily share price and provides certain other administrative services to the fund. T. Rowe Price Services, Inc., provides shareholder and administrative services in its capacity as the fund’s transfer and dividend disbursing agent. T. Rowe Price Retirement Plan Services, Inc., provides subac-counting and recordkeeping services for certain retirement accounts invested in the fund. For the year ended May 31, 2006, expenses incurred pursuant to these service agreements were $109,000 for Price Associates, $623,000 for T. Rowe Price Services, Inc., and $130,000 for T. Rowe Price Retirement Plan Services, Inc. The total amount payable at period end pursuant to these service agreements is reflected as Due to Affiliates in the accompanying financial statements.

The fund is also one of several mutual funds sponsored by Price Associates (underlying Price funds) in which the T. Rowe Price Spectrum Funds (Spectrum Funds) may invest. The Spectrum Funds do not invest in the underlying Price funds for the purpose of exercising management or control. Pursuant to a special servicing agreement, expenses associated with the operation of the Spectrum Funds are borne by each underlying Price fund to the extent of estimated savings to it and in proportion to the average daily value of its shares owned by the Spectrum Funds. Expenses allocated under this agreement are reflected as shareholder servicing expense in the accompanying financial statements. For the year ended May 31, 2006, the fund was allocated $931,000 of Spectrum Funds’ expenses, of which $617,000 related to services provided by Price. The amount payable at period end pursuant to this agreement is reflected as Due to Affiliates in the accompanying financial statements. At May 31, 2006, approximately 41% of the outstanding shares of the fund were held by the Spectrum Funds.

The fund may invest in the T. Rowe Price Reserve Investment Fund and the T. Rowe Price Government Reserve Investment Fund (collectively, the T. Rowe Price Reserve Funds), open-end management investment companies managed by Price Associates and affiliates of the fund. The T. Rowe Price Reserve Funds are offered as cash management options to mutual funds, trusts, and other accounts managed by Price Associates and/or its affiliates, and are not available for direct purchase by members of the public. The T. Rowe Price Reserve Funds pay no investment management fees. During the year ended May 31, 2006, dividend income from the T. Rowe Price Reserve Funds totaled $3,664,000, and the value of shares of the T. Rowe Price Reserve Funds held at May 31, 2006, and May 31, 2005, was $46,458,000 and $279,965,000, respectively.

REPORT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM 

To the Board of Directors and Shareholders of T. Rowe Price GNMA Fund

In our opinion, the accompanying statement of assets and liabilities, including the portfolio of investments, and the related statements of operations and of changes in net assets and the financial highlights present fairly, in all material respects, the financial position of T. Rowe Price GNMA Fund (the “Fund”) at May 31, 2006, the results of its operations for the year then ended, the changes in its net assets for each of the two years in the period then ended and the financial highlights for each of the five years in the period then ended, in conformity with accounting principles generally accepted in the United States of America. These financial statements and financial highlights (hereafter referred to as “financial statements”) are the responsibility of the Fund’s management; our responsibility is to express an opinion on these financial statements based on our audits. We conducted our audits of these financial statements in accordance with the standards of the Public Company Accounting Oversight Board (United States). Those standards require that we plan and perform the audit to obtain reasonable assurance about whether the financial statements are free of material misstatement. An audit includes examining, on a test basis, evidence supporting the amounts and disclosures in the financial statements, assessing the accounting principles used and significant estimates made by management, and evaluating the overall financial statement presentation. We believe that our audits, which included confirmation of securities at May 31, 2006 by correspondence with the custodian and brokers, and by agreement to the underlying ownership records for T. Rowe Price Reserve Investment Fund, provide a reasonable basis for our opinion.

PricewaterhouseCoopers LLP
Baltimore, Maryland
July 12, 2006

TAX INFORMATION (UNAUDITED) FOR THE TAX YEAR ENDED 5/31/06 

We are providing this information as required by the Internal Revenue Code. The amounts shown may differ from those elsewhere in this report because of differences between tax and financial reporting requirements.

The fund’s distributions to shareholders included $830,000 from short-term capital gains.

INFORMATION ON PROXY VOTING POLICIES, PROCEDURES, AND RECORDS 

A description of the policies and procedures used by T. Rowe Price funds and portfolios to determine how to vote proxies relating to portfolio securities is available in each fund’s Statement of Additional Information, which you may request by calling 1-800-225-5132 or by accessing the SEC’s Web site, www.sec.gov. The description of our proxy voting policies and procedures is also available on our Web site, www.troweprice.com. To access it, click on the words “Company Info” at the top of our homepage for individual investors. Then, in the window that appears, click on the “Proxy Voting Policy” navigation button in the top left corner.

Each fund’s most recent annual proxy voting record is available on our Web site and through the SEC’s Web site. To access it through our Web site, follow the directions above, then click on the words “Proxy Voting Record” at the bottom of the Proxy Voting Policy page.

HOW TO OBTAIN QUARTERLY PORTFOLIO HOLDINGS 

The fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission for the first and third quarters of each fiscal year on Form N-Q. The fund’s Form N-Q is available electronically on the SEC’s Web site (www.sec.gov); hard copies may be reviewed and copied at the SEC’s Public Reference Room, 450 Fifth St. N.W., Washington, DC 20549. For more information on the Public Reference Room, call 1-800-SEC-0330.

APPROVAL OF INVESTMENT MANAGEMENT AGREEMENT 

On March 8, 2006, the fund’s Board of Directors unanimously approved the investment advisory contract (Contract) between the fund and its investment manager, T. Rowe Price Associates, Inc. (Manager). The Board considered a variety of factors in connection with its review of the Contract, also taking into account information provided by the Manager during the course of the year, as discussed below:

Services Provided by the Manager
The Board considered the nature, quality, and extent of the services provided to the fund by the Manager. These services included, but were not limited to, management of the fund’s portfolio and a variety of activities related to portfolio management. The Board also reviewed the background and experience of the Manager’s senior management team and investment personnel involved in the management of the fund. The Board concluded that it was satisfied with the nature, quality, and extent of the services provided by the Manager.

Investment Performance of the Fund
The Board reviewed the fund’s average annual total return over the 1-, 3-, 5-, and 10-year periods as well as the fund’s year-by-year returns and compared these returns with a wide variety of previously agreed upon comparable performance measures and market data, including those supplied by Lipper and Morningstar, which are independent providers of mutual fund data. On the basis of this evaluation and the Board’s ongoing review of investment results, the Board concluded that the fund’s performance was satisfactory.

Costs, Benefits, Profits, and Economies of Scale
The Board reviewed detailed information regarding the revenues received by the Manager under the Contract and other benefits that the Manager (and its affiliates) may have realized from its relationship with the fund, including research received under “soft dollar” agreements. The Board noted that the use of soft dollars as a means of paying for third-party, non-broker research had been eliminated. The Board also received information on the estimated costs incurred and profits realized by the Manager and its affiliates from advising T. Rowe Price mutual funds, as well as estimates of the gross profits realized from managing the fund in particular. The Board concluded that the Manager’s profits were reasonable in light of the services provided to the fund. The Board also considered whether the fund or other funds benefit under the fee levels set forth in the Contract from any economies of scale realized by the Manager. Under the Contract, the fund pays a fee to the Manager composed of two components—a group fee rate based on the aggregate assets of certain T. Rowe Price mutual funds (including the fund) that declines at certain asset levels and an individual fund fee rate that is assessed on the assets of the fund. The Board concluded that the advisory fee structure for the fund continued to provide for a reasonable sharing of benefits from economies of scale with the fund’s investors.

Fees
The Board reviewed the fund’s management fee rate, operating expenses, and total expense ratio and compared them with fees and expenses of other comparable funds based on information and data supplied by Lipper. The information provided to the Board that the fund’s management fee rate was above the median of certain groups of comparable funds but at or below the median of other groups of comparable funds. The information also indicated that the fund’s expense ratio was generally below the median of comparable funds. The Board also reviewed the fee schedules for comparable privately managed accounts of the Manager and its affiliates. Management informed the Board that the Manager’s responsibilities for privately managed accounts are more limited than its responsibilities for the fund and other T. Rowe Price mutual funds that it or its affiliates advise. On the basis of the information provided, the Board concluded that the fees paid by the fund under the Contract were reasonable.

Approval of the Contract
As noted, the Board approved the continuation of the Contract. No single factor was considered in isolation or to be determinative to the decision. Rather, the Board concluded, in light of a weighting and balancing of all factors considered, that it was in the best interests of the fund to approve the continuation of the Contract, including the fees to be charged for services thereunder.

ABOUT THE FUND’S TRUSTEES AND OFFICERS 

Your fund is governed by a Board of Trustees that meets regularly to review performance, investment programs, compliance matters, advisory fees and expenses, service providers, and other business matters, and is responsible for protecting the interests of shareholders. At least 75% of the fund’s trustees are independent of T. Rowe Price Associates, Inc. (T. Rowe Price); “inside” trustees are officers of T. Rowe Price. The Board of Trustees elects the fund’s officers, who are listed in the final table. The business address of each trustee and officer is 100 East Pratt Street, Baltimore, MD 21202. The Statement of Additional Information includes additional information about the fund trustees and is available without charge by calling a T. Rowe Price representative at 1-800-225-5132.

Independent Trustees
Name
(Year of Birth)	Principal Occupation(s) During Past 5 Years and
Year Elected*	Directorships of Other Public Companies
Jeremiah E. Casey	Director, Allfirst Financial, Inc. (previously First Maryland Bankcorp)
(1940)	(1983 to 2002); Director, National Life Insurance (2001 to 2005);
2006	Director, The Rouse Company, real estate developers (1990 to 2004)
Anthony W. Deering	Chairman, Exeter Capital, LLC, a private investment firm (2004 to
(1945)	present); Director, Vornado Real Estate Investment Trust (3/04 to
1985	present); Director, Mercantile Bankshares (4/03 to present); Member,
	Advisory Board, Deutsche Bank North America (2004 to present);
	Director, Chairman of the Board, and Chief Executive Officer, The
	Rouse Company, real estate developers (1997 to 2004)
Donald W. Dick, Jr.	Principal, EuroCapital Advisors, LLC, an acquisition and management
(1943)	advisory firm; Chairman, President, and Chief Executive Officer, The
2001	Haven Group, a custom manufacturer of modular homes (1/04 to
	present)
David K. Fagin	Chairman and President, Nye Corporation (6/88 to present); Director,
(1938)	Canyon Resources Corp. and Golden Star Resources Ltd. (5/92 to
2001	present), and Pacific Rim Mining Corp. (2/02 to present)
Karen N. Horn	Managing Director and President, Global Private Client Services,
(1943)	Marsh Inc. (1999 to 2003); Managing Director and Head of
2003	International Private Banking, Bankers Trust (1996 to 1999); Director,
	Georgia Pacific, Eli Lilly and Company, and Simon Property Group
Theo C. Rodgers	President, A&R Development Corporation
(1941)
2005
John G. Schreiber	Owner/President, Centaur Capital Partners, Inc., a real estate invest-
(1946)	ment company; Partner, Blackstone Real Estate Advisors, L.P.;
1992	Director, AMLI Residential Properties Trust

* Each independent trustee oversees 113 T. Rowe Price portfolios and serves until retirement, resignation, or election of a successor.

Inside Trustees
Name
(Year of Birth)
Year Elected*
[Number of T. Rowe Price	Principal Occupation(s) During Past 5 Years and
Portfolios Overseen]	Directorships of Other Public Companies
Edward C. Bernard	Director and Vice President, T. Rowe Price and T. Rowe Price Group,
(1956)	Inc.; Chairman of the Board, Director, and President, T. Rowe Price
2006	Investment Services, Inc.; Chairman of the Board and Director,
[113]	T. Rowe Price Retirement Plan Services, Inc., T. Rowe Price Services,
	Inc., and T. Rowe Price Savings Bank; Director, T. Rowe Price Global
	Asset Management Limited and T. Rowe Price Global Investment
	Services Limited; Chief Executive Officer, Chairman of the Board,
	Director, and President, T. Rowe Price Trust Company; Chairman of
	the Board, all funds
Mary J. Miller, CFA	Director and Vice President, T. Rowe Price; Vice President, T. Rowe
(1955)	Price Group, Inc.; Vice President, GNMA Fund
2004
[37]

* Each inside trustee serves until retirement, resignation, or election of a successor.

Officers
Name (Year of Birth)
Title and Fund(s) Served	Principal Occupation(s)
Connice A. Bavely, CFA (1951)	Vice President, T. Rowe Price and T. Rowe Price
President, GNMA Fund	Group, Inc.
Joseph A. Carrier, CPA (1960)	Vice President, T. Rowe Price, T. Rowe Price
Treasurer, GNMA Fund	Group, Inc., T. Rowe Price Investment Services,
	Inc., and T. Rowe Price Trust Company
Roger L. Fiery III, CPA (1959)	Vice President, T. Rowe Price, T. Rowe Price
Vice President, GNMA Fund	Group, Inc., T. Rowe Price International, Inc.,
	and T. Rowe Price Trust Company
John R. Gilner (1961)	Chief Compliance Officer and Vice President,
Chief Compliance Officer, GNMA Fund	T. Rowe Price; Vice President, T. Rowe Price
	Group, Inc., and T. Rowe Price Investment
	Services, Inc.
Gregory S. Golczewski (1966)	Vice President, T. Rowe Price and T. Rowe Price
Vice President, GNMA Fund	Trust Company
Henry H. Hopkins (1942)	Director and Vice President, T. Rowe Price
Vice President, GNMA Fund	Investment Services, Inc., T. Rowe Price
	Services, Inc., and T. Rowe Price Trust Company;
	Vice President, T. Rowe Price, T. Rowe Price
	Group, Inc., T. Rowe Price International, Inc.,
	and T. Rowe Price Retirement Plan Services, Inc.
Keir R. Joyce (1972)	Vice President, T. Rowe Price
Vice President, GNMA Fund
Alan D. Levenson, Ph.D. (1958)	Vice President, T. Rowe Price and T. Rowe Price
Vice President, GNMA Fund	Group, Inc.
Patricia B. Lippert (1953)	Assistant Vice President, T. Rowe Price and
Secretary, GNMA Fund	T. Rowe Price Investment Services, Inc.
Julie L. Waples (1970)	Vice President, T. Rowe Price
Vice President, GNMA Fund
John D. Wells (1960)	Vice President, T. Rowe Price, T. Rowe Price
Vice President, GNMA Fund	Group, Inc., and T. Rowe Price Savings Bank

Unless otherwise noted, officers have been employees of T. Rowe Price or T. Rowe Price International for at least five years.

Item 2. Code of Ethics.

The registrant has adopted a code of ethics, as defined in Item 2 of Form N-CSR, applicable to its principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions. A copy of this code of ethics is filed as an exhibit to this Form N-CSR. No substantive amendments were approved or waivers were granted to this code of ethics during the period covered by this report.

Item 3. Audit Committee Financial Expert.

The registrant’s Board of Directors/Trustees has determined that Mr. Donald W. Dick Jr. qualifies as an audit committee financial expert, as defined in Item 3 of Form N-CSR. Mr. Dick is considered independent for purposes of Item 3 of Form N-CSR.

Item 4. Principal Accountant Fees and Services.

(a) – (d) Aggregate fees billed to the registrant for the last two fiscal years for professional services rendered by the registrant’s principal accountant were as follows:

	2006	2005
Audit Fees	$11,362	$7,961
Audit-Related Fees	1,007	939
Tax Fees	1,883	1,399
All Other Fees	150	307

Audit fees include amounts related to the audit of the registrant’s annual financial statements and services normally provided by the accountant in connection with statutory and regulatory filings. Audit-related fees include amounts reasonably related to the performance of the audit of the registrant’s financial statements and specifically include the issuance of a report on internal controls. Tax fees include amounts related to services for tax compliance, tax planning, and tax advice. The nature of these services specifically includes the review of distribution calculations and the preparation of Federal, state, and excise tax returns. Reclassification from tax fees to audit fees of fiscal 2005 amounts related to the auditing of tax disclosures within the registrant’s annual financial statements has been made in order to conform to fiscal 2006 presentation. All other fees include the registrant’s pro-rata share of amounts for agreed-upon procedures in conjunction with service contract approvals by the registrant’s Board of Directors/Trustees.

(e)(1) The registrant’s audit committee has adopted a policy whereby audit and non-audit services performed by the registrant’s principal accountant for the registrant, its investment adviser, and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant require pre-approval in advance at regularly scheduled audit committee meetings. If such a service is required between regularly scheduled audit committee meetings, pre-approval may be authorized by one audit committee member with ratification at the next scheduled audit committee meeting. Waiver of pre-approval for audit or non-audit services requiring fees of a de minimis amount is not permitted.

    (2) No services included in (b) – (d) above were approved pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

(f) Less than 50 percent of the hours expended on the principal accountant’s engagement to audit the registrant’s financial statements for the most recent fiscal year were attributed to work performed by persons other than the principal accountant’s full-time, permanent employees.

(g) The aggregate fees billed for the most recent fiscal year and the preceding fiscal year by the registrant’s principal accountant for non-audit services rendered to the registrant, its investment adviser, and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant were $883,000 and $785,000, respectively, and were less than the aggregate fees billed for those same periods by the registrant’s principal accountant for audit services rendered to the T. Rowe Price Funds. Preceding fiscal year amount reflects the reclassification of tax fees described in (a) – (d) above.

(h) All non-audit services rendered in (g) above were pre-approved by the registrant’s audit committee. Accordingly, these services were considered by the registrant’s audit committee in maintaining the principal accountant’s independence.

Item 5. Audit Committee of Listed Registrants.

Not applicable.

Item 6. Schedule of Investments.

Not applicable. The complete schedule of investments is included in Item 1 of this Form N-CSR.

Item 7. Disclosure of Proxy Voting Policies and Procedures for Closed-End Management Investment Companies.

Not applicable.

Item 8. Portfolio Managers of Closed-End Management Investment Companies.

Not applicable.

Item 9. Purchases of Equity Securities by Closed-End Management Investment Company and Affiliated Purchasers.

Not applicable.

Item 10. Submission of Matters to a Vote of Security Holders.

Not applicable.

Item 11. Controls and Procedures.

(a) The registrant’s principal executive officer and principal financial officer have evaluated the registrant’s disclosure controls and procedures within 90 days of this filing and have concluded that the registrant’s disclosure controls and procedures were effective, as of that date, in ensuring that information required to be disclosed by the registrant in this Form N-CSR was recorded, processed, summarized, and reported timely.

(b) The registrant’s principal executive officer and principal financial officer are aware of no change in the registrant’s internal control over financial reporting that occurred during the registrant’s second fiscal quarter covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Exhibits.

(a)(1) The registrant’s code of ethics pursuant to Item 2 of Form N-CSR is attached.

    (2) Separate certifications by the registrant's principal executive officer and principal financial officer, pursuant to Section 302 of the Sarbanes-Oxley Act of 2002 and required by Rule 30a-2(a) under the Investment Company Act of 1940, are attached.

    (3) Written solicitation to repurchase securities issued by closed-end companies: not applicable.

(b) A certification by the registrant's principal executive officer and principal financial officer, pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 and required by Rule 30a-2(b) under the Investment Company Act of 1940, is attached.

SIGNATURES
	Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment
Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the
undersigned, thereunto duly authorized.
T. Rowe Price GNMA Fund
By	/s/ Edward C. Bernard
	Edward C. Bernard
	Principal Executive Officer
Date	July 18, 2006
	Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment
Company Act of 1940, this report has been signed below by the following persons on behalf of
the registrant and in the capacities and on the dates indicated.
By	/s/ Edward C. Bernard
	Edward C. Bernard
	Principal Executive Officer
Date	July 18, 2006
By	/s/ Joseph A. Carrier
	Joseph A. Carrier
	Principal Financial Officer
Date	July 18, 2006