UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED
MANAGEMENT INVESTMENT COMPANIES

Investment Company Act File Number: 811-4441

T. Rowe Price GNMA Fund

(Exact name of registrant as specified in charter)

100 East Pratt Street, Baltimore, MD 21202

(Address of principal executive offices)

David Oestreicher

100 East Pratt Street, Baltimore, MD 21202

(Name and address of agent for service)

Registrant’s telephone number, including area code: (410) 345-2000

Date of fiscal year end: May 31

Date of reporting period: November 30, 2011

The views and opinions in this report were current as of November 30, 2011. 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, 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.

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Investors in longer-term bonds, including GNMAs, enjoyed respectable overall returns during the six months ended November 30, 2011. GNMAs and other mortgage-backed securities (MBS) benefited from strong demand and a low pace of prepayments, but the asset class did not fare as well as Treasuries, as investors remained exceptionally cautious and worried about changes in housing policy. The GNMA Fund slightly outperformed its peer group average over the period but lagged the Barclays Capital U.S. GNMA Index.

The GNMA Fund returned 2.88% for the six-month period ended November 30, 2011. As shown in the Performance Comparison table, the portfolio trailed the Barclays Capital U.S. GNMA Index while slightly outpacing the Lipper GNMA Funds Average over the period.

The past six months witnessed growing concerns over the resilience of global growth. Investors were particularly worried about the debt crisis in Europe, which threatened both the U.S. financial system and exports. U.S. economic growth slowed to a crawl in the early summer, partly in response to higher oil prices and supply disruptions from the Japanese earthquake and tsunami. While growth picked up somewhat in the third quarter, a political showdown over the debt limit in Washington drained consumer confidence and led to a fiscal stalemate and a downgrade of the U.S. government’s long-term credit rating. Worries grew that the U.S. might follow Europe into a “double dip” recession, although data late in the period suggested that the economy was continuing to expand, albeit at a meager pace that left unemployment at elevated levels.

With fiscal policy effectively sidelined, investors kept a close eye on the Federal Reserve and its willingness and capacity to engage in further monetary stimulus. In late summer, Fed officials announced their intention to keep short-term interest rates near 0% for the next two years, and on September 21, a divided Federal Reserve policymaking committee announced a new round of monetary stimulus. Dubbed Operation Twist, the Fed’s plan involved trading $400 billion of its short-term Treasury holdings for longer-term issues in an effort to spur borrowing and aid the housing sector. The Fed also announced its intention to resume mortgage purchases. Many investors worried that lowering borrowing costs would accomplish little in the face of high unemployment, however.

Market uncertainty and the resulting preference by investors for high-quality fixed income assets led to a sharp reversal in bond yields during the latter half of the year. As investor optimism evaporated, 10-year Treasury yields fell from a high of well over 3.5% in the first quarter of 2011 to near historical lows in the autumn. Volatility within the financial markets led to disparate effects across fixed income sectors despite the Fed’s accommodative stance. U.S. Treasuries posted their best performance since the start of the financial crisis in 2008, while the investment-grade corporate sector and certain parts of the mortgage market struggled to keep pace. However, asset-backed and commercial mortgage-backed securities (CMBS) managed to exceed the returns on comparable Treasuries.

Attractive fundamentals, healthy demand, and a historically lower risk profile relative to other fixed income sectors led GNMAs to outpace competing mortgage and investment-grade issues over the past six months. GNMA issuance continued to grow during the most recent period, helping to increase GNMAs’ share of the agency-backed MBS sector. The increase in net supply was met with broad-based demand, however, as historically low interest rates, tepid bank loan growth (a competing form of debt), and a weaker dollar attracted investors to the sector.

In addition, Federal Reserve policy actions supported GNMAs along with the rest of the agency MBS sector—loans issued by Fannie Mae and Freddie Mac. Central bank officials surprised investors in late September with their decision to reinvest maturing agency corporate debt and principal payments from the Fed’s MBS portfolio back into the market. The Fed’s action was intended to support lower mortgage rates and ease building pressure from European markets, which was leading to tightening credit for consumers and deteriorating financial conditions.

While the supply/demand balance in the market boosted MBS performance, fundamentals were also supportive. Though low absolute rates have historically spurred increased refinance activity from borrowers, more restrictive underwriting criteria from mortgage originators, elevated unemployment, and a weaker housing market led to only manageable increases in prepayment activity. Muted refinance activity and the subsequent slower-than-expected principal repayment resulted in greater income for investors and considerable price appreciation as yields fell.

GNMAs experienced some volatility over the past six months, however, leading them to underperform U.S. Treasuries. Investors grew more cautious due to increased concerns over the European debt crisis, as well as the rating agencies’ downgrade of the long-term U.S. credit rating. Uncertainty over domestic housing policy—in particular, the possibility that the government might encourage more mortgage refinancing—also weighed on the sector.

The fund’s performance relative to its peers benefited from our selection of holdings within the GNMA mortgage sector. These included increased exposure to securities that are “to be announced” prior to trade settlement (TBAs), as well as mortgage pass-through securities that may have been issued during the peak in the housing boom but that have particularly attractive collateral characteristics that protect investors from heightened prepayment risk. Conversely, the fund’s strategy of diversifying risk through allocations to non-GNMA securities detracted from results as investors grew more cautious. CMBS, non-agency residential securities, and MBS backed by Fannie Mae or Freddie Mac underperformed GNMAs. Positioning the fund for higher interest rates by maintaining a shorter-duration posture (a measure of the price sensitivity of fixed income securities) also detracted a bit from results.

Our outlook for GNMAs and other MBS is generally positive, but we remain cognizant of several risks. Stable interest rates and policies supportive of MBS should provide a favorable environment for mortgage investors. Nevertheless, we are keeping an eye out for disruptions given the heightened volatility in the markets, low mortgage rates, and uncertainty surrounding housing reform. We will continue to rely on the careful research of our staff of in-house analysts as we seek opportunities for our shareholders.

Andrew McCormick
President of the fund and chairman of the Investment Advisory Committee

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.

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.

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

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 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.

Lipper averages: The averages of available mutual fund performance returns for specified time periods in categories defined by Lipper Inc.

SEC yield (30-day): A method of calculating a fund’s yield that assumes all portfolio securities are held until maturity. Yield will vary and is not guaranteed.

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.

Weighted average maturity: A measure of a fund’s interest rate sensitivity. In general, the longer the average maturity, the greater the fund’s sensitivity to interest rate changes. The weighted average maturity may take into account the interest rate readjustment dates for certain securities. Money funds must maintain a weighted average maturity of less than 60 days.

Yield curve: A graph depicting the relationship between yields and maturity dates for a set of similar securities. These curves are in constant flux. One of the key activities in managing any fixed income portfolio is to study the trends reflected by yield curves.

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.

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 expenses based on the fund’s actual returns. You may use the information on 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 on 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 account service fee of $20, generally for accounts with less than $10,000 ($1,000 for UGMA/UTMA). The fee is waived for any investor whose T. Rowe Price mutual fund accounts total $50,000 or more; accounts employing automatic investing; accounts electing to receive electronic delivery of account statements, transaction confirmations, prospectuses, and shareholder reports; accounts of an investor who is a T. Rowe Price Preferred Services, Personal Services, or Enhanced Personal Services client (enrollment in these programs generally requires T. Rowe Price assets of at least $100,000); 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.

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 high overall credit quality and moderate price fluctuation by investing at least 80% of its total assets in GNMA securities backed by the full faith and credit of the U.S. government.

Basis of Preparation The accompanying financial statements were prepared in accordance with accounting principles generally accepted in the United States of America (GAAP), which require the use of estimates made by management. Management believes that estimates and valuations are appropriate; however, actual results may differ from those estimates, and the valuations reflected in the accompanying financial statements may differ from the value ultimately realized upon sale or maturity.

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. Paydown gains and losses are recorded as an adjustment to interest income. Dividends received from mutual fund investments are reflected as dividend income; capital gain distributions are reflected as realized gain/loss. Earnings on investments recognized as partnerships for federal income tax purposes reflect the tax character of such earnings. Dividend income and capital gain distributions are recorded on the ex-dividend date. Income tax-related interest and penalties, if incurred, would be recorded as income tax expense. Investment transactions are accounted for on the trade date. Realized gains and losses are reported on the identified cost basis. Distributions to shareholders are recorded on the ex-dividend date. Income distributions are declared daily and paid monthly. Capital gain distributions, if any, are generally declared and paid by the fund annually.

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

The fund’s financial instruments are reported at fair value as defined by GAAP. The fund determines the values of its assets and liabilities 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.

Valuation Methods Debt securities are generally traded in the over-the-counter (OTC) market. Securities with remaining maturities of one year or more at the time of acquisition are valued at prices furnished by dealers who make markets in such securities or by an independent pricing service, which considers the 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 remaining maturities of less than one year at the time of acquisition generally use amortized cost in local currency to approximate fair value. However, if amortized cost is deemed not to reflect fair value or the fund holds a significant amount of such securities with remaining maturities of more than 60 days, the securities are valued at prices furnished by dealers who make markets in such securities or by an independent pricing service.

Investments in mutual funds are valued at the mutual fund’s closing net asset value per share on the day of valuation. Investments in private investment companies are valued at the entity’s net asset value (or equivalent) as of the valuation date.

Other investments, including restricted securities and private placements, and those financial instruments 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 (the Board). Subject to oversight by the Board, the Valuation Committee develops pricing-related policies and procedures and approves all fair-value determinations. The Valuation Committee regularly makes good faith judgments, using a wide variety of sources and information, to establish and adjust valuations of certain securities as events occur and circumstances warrant. For instance, in determining the fair value of private-equity instruments, the Valuation Committee considers a variety of factors, including the company’s business prospects, its financial performance, strategic events impacting the company, relevant valuations of similar companies, new rounds of financing, and any negotiated transactions of significant size between other investors in the company. Because any fair-value determination involves a significant amount of judgment, there is a degree of subjectivity inherent in such pricing decisions.

Valuation Inputs Various inputs are used to determine the value of the fund’s financial instruments. These inputs are summarized in the three broad levels listed below:

Level 2 – observable inputs other than Level 1 quoted prices (including, but not limited to, quoted prices for similar financial instruments, interest rates, prepayment speeds, and credit risk)

Observable inputs are those based on market data obtained from sources independent of the fund, and unobservable inputs reflect the fund’s own assumptions based on the best information available. The input levels are not necessarily an indication of the risk or liquidity associated with financial instruments at that level. The following table summarizes the fund’s financial instruments, based on the inputs used to determine their values on November 30, 2011:

Following is a reconciliation of the fund’s Level 3 holdings for the six months ended November 30, 2011. Gain (loss) reflects both realized and change in unrealized gain (loss) on Level 3 holdings during the period, if any, and is included on the accompanying Statement of Operations. The change in unrealized gain (loss) on Level 3 instruments held at November 30, 2011, totaled $(206,000) for the six months ended November 30, 2011.

During the six months ended November 30, 2011, the fund invested in derivative instruments. As defined by GAAP, a derivative is a financial instrument whose value is derived from an underlying security price, foreign exchange rate, interest rate, index of prices or rates, or other variable; it requires little or no initial investment and permits or requires net settlement. The fund invests in derivatives only if the expected risks and rewards are consistent with its investment objectives, policies, and overall risk profile, as described in its prospectus and Statement of Additional Information. The fund may use derivatives for a variety of purposes, such as seeking to hedge against declines in principal value, increase yield, invest in an asset with greater efficiency and at a lower cost than is possible through direct investment, or to adjust portfolio duration and credit exposure. The risks associated with the use of derivatives are different from, and potentially much greater than, the risks associated with investing directly in the instruments on which the derivatives are based. Investments in derivatives can magnify returns positively or negatively; however, the fund at all times maintains sufficient cash reserves, liquid assets, or other SEC-permitted asset types to cover the settlement obligations under its open derivative contracts.

The fund values its derivatives at fair value, as described below and in Note 2, and recognizes changes in fair value currently in its results of operations. Accordingly, the fund does not follow hedge accounting, even for derivatives employed as economic hedges. The fund does not offset the fair value of derivative instruments against the right to reclaim or obligation to return collateral. As of November 30, 2011, the fund held no derivative instruments.

Additionally, the amount of gains and losses on derivative instruments recognized in fund earnings during the six months ended November 30, 2011, and the related location on the accompanying Statement of Operations is summarized in the following table by primary underlying risk exposure:

Futures Contracts The fund is subject to interest rate risk in the normal course of pursuing its investment objectives and uses futures contracts to help manage such risk. The fund may enter into futures contracts to manage exposure to interest rate and yield curve movements, security prices, foreign currencies, credit quality, and mortgage prepayments; as an efficient means of adjusting exposure to all or part of a target market; to enhance income; as a cash management tool; and/or to adjust portfolio duration and credit exposure. A futures contract provides for the future sale by one party and purchase by another of a specified amount of a particular underlying financial instrument at an agreed-upon price, date, time, and place. The fund currently invests only in exchange-traded futures, which generally are standardized as to maturity date, underlying financial instrument, and other contract terms. Upon entering into a futures contract, the fund is required to deposit with the broker cash or securities in an amount equal to a certain percentage of the contract value (initial margin deposit); the margin deposit must then be maintained at the established level over the life of the contract. Subsequent payments are made or received by the fund each day to settle daily fluctuations in the value of the contract (variation margin), which reflect changes in the value of the underlying financial instrument. Variation margin is recorded as unrealized gain or loss until the contract is closed. The value of a futures contract included in net assets is the amount of unsettled variation margin; net variation margin receivable is reflected as an asset, and net variation margin payable is reflected as a liability on the accompanying Statement of Assets and Liabilities. Risks related to the use of futures contracts include possible illiquidity of the futures markets, contract prices that can be highly volatile and imperfectly correlated to movements in hedged security values and/or interest rates, and potential losses in excess of the fund’s initial investment. During the six months ended November 30, 2011, the fund’s exposure to futures, based on underlying notional amounts, was generally between 0% and 9% of net assets.

Interest Rate Swaps The fund is subject to interest rate risk in the normal course of pursuing its investment objectives and uses swap contracts to help manage such risk. The fund may use swaps in an effort to manage exposure to changes in interest rates, inflation rates, and credit quality; to adjust overall exposure to certain markets; to enhance total return or protect the value of portfolio securities; to serve as a cash management tool; and/or to adjust portfolio duration and credit exposure. Interest rate swaps are agreements to exchange cash flows based on the difference between specified interest rates applied to a notional principal amount for a specified period of time. The value of a swap included in net assets is the unrealized gain or loss on the contract plus or minus any unamortized premiums paid or received, respectively. Appreciated swaps and premiums paid are reflected as assets, and depreciated swaps and premiums received are reflected as liabilities on the accompanying Statement of Assets and Liabilities. Net periodic receipts or payments required by swaps are accrued daily and are recorded as realized gain or loss for financial reporting purposes when settled; fluctuations in the fair value of swaps are reflected in the change in net unrealized gain or loss and are reclassified to realized gain or loss upon termination prior to maturity or cash settlement. Risks related to the use of interest rate swaps include the potential for unanticipated movements in interest and/or currency rates, the possible failure of a counterparty to perform in accordance with the terms of the swap agreements, potential government regulation that could adversely affect the fund’s swap investments, and potential losses in excess of the fund’s initial investment. During the six months ended November 30, 2011, the fund’s exposure to swaps, based on underlying notional amounts, was generally between 0% and 9% of net assets.

Consistent with its investment objective, the fund engages in the following practices to manage exposure to certain risks and/or to 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.

Restricted Securities The fund may invest in securities that are subject to legal or contractual restrictions on resale. Prompt sale of such securities at an acceptable price may be difficult and may involve substantial delays and additional costs.

TBA Purchase and Sale Commitments During the six months ended November 30, 2011, the fund entered into to be announced (TBA) purchase and/or sale commitments, pursuant to which it agrees to purchase or sell, respectively, mortgage-backed securities for a fixed unit price, with payment and delivery at a scheduled future date beyond the customary settlement period for such mortgage-backed securities. With TBA transactions, the particular securities to be delivered are not identified at the 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 TBA purchase transactions with the intention of taking possession of the underlying mortgage securities; however, for either purchase or sale transactions, the fund also may extend the settlement by “rolling” the transaction. Until settlement, the fund maintains cash reserves and liquid assets sufficient to settle its TBA commitments.

Dollar Rolls During the six months ended November 30, 2011, 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 to be 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.

T. Rowe Price Term Asset-Backed Opportunity Fund, L.L.C. During the six months ended November 30, 2011, the fund was invested in the T. Rowe Price Term Asset-Backed Opportunity Fund, L.L.C. (private fund), a private investment company managed by T. Rowe Price Associates, Inc. that participates in the Term Asset-Backed Securities Loan Facility (TALF) program created and administered by the Federal Reserve Bank of New York (FRBNY). The TALF program provided eligible borrowers with term loans secured by eligible asset-backed securities and/or commercial mortgage-backed securities, which were either owned by the borrower or purchased by the borrower and subsequently pledged as collateral for a TALF loan. TALF loans generally are nonrecourse in nature. The private fund is treated as a partnership for federal income tax purposes. It has a limited life extending five years from the date on which the TALF program closed for any new loans, which was June 30, 2010. The private fund can have two possible extensions (one year each) with the consent of a majority of its investors. Invested capital generally will be returned to investors as underlying securities are liquidated and the TALF loans are repaid or mature, with the balance paid at maturity of the private fund. Ownership interests in the private fund may not be redeemed, sold, or assigned. As of November 30, 2011, outstanding capital commitments may no longer be called by the private fund.

Counterparty Risk and Collateral The fund has entered into collateral agreements with certain counterparties to mitigate counterparty risk associated with certain over-the-counter (OTC) financial instruments, including swaps, forward currency exchange contracts, TBA purchase commitments, and OTC options (collectively, covered OTC instruments). Subject to certain minimum exposure requirements (which typically range from $100,000 to $500,000), collateral requirements generally are determined and transfers made based on the net aggregate unrealized gain or loss on all OTC instruments covered by a particular collateral agreement with a specified counterparty. Collateral, both pledged by the fund to a counterparty and pledged by a counterparty to the fund, is held in a segregated account by a third-party agent and can be in the form of cash or debt securities issued by the U.S. government or related agencies. Securities posted as collateral by the fund to a counterparty are so noted in the accompanying Portfolio of Investments and remain in the fund’s net assets. As of November 30, 2011, no collateral had been posted by the fund to counterparties. In accordance with GAAP, cash pledged by counterparties to the fund is included in the fund’s net assets; however, securities pledged by counterparties to the fund are not recorded by the fund. As of November 30, 2011, collateral pledged by counterparties to the fund consisted of $44,000 cash and securities valued at $82,000.

At any point in time, the fund’s risk of loss from counterparty credit risk on covered OTC instruments is the aggregate unrealized gain on appreciated covered OTC instruments in excess of collateral, if any, pledged by the counterparty to the fund. Counterparty risk related to exchange-traded futures and options contracts is minimal because the exchange’s clearinghouse provides protection against counterparty defaults. Generally, for exchange-traded derivatives such as futures and options, each broker, in its sole discretion, may change margin requirements applicable to the fund. In accordance with the terms of the relevant derivatives agreements, counterparties to OTC derivatives may be able to terminate derivative contracts prior to maturity after the occurrence of certain stated events, such as a decline in net assets above a certain percentage or a failure by the fund to perform its obligations under the contract. Upon termination, all transactions would typically be liquidated and a net amount would be owed by or payable to the fund.

Other Purchases and sales of portfolio securities other than short-term and U.S. government securities aggregated $44,083,000 and $48,153,000, respectively, for the six months ended November 30, 2011. Purchases and sales of U.S. government securities aggregated $3,263,147,000 and $3,055,441,000, respectively, for the six months ended November 30, 2011.

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. Distributions determined in accordance with federal income tax regulations may differ 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 but are not adjusted for temporary differences. The amount and character of tax-basis distributions and composition of net assets are finalized at fiscal year-end; accordingly, tax-basis balances have not been determined as of the date of this report.

At November 30, 2011, the cost of investments for federal income tax purposes was $1,840,136,000. Net unrealized gain aggregated $50,016,000 at period-end, of which $56,373,000 related to appreciated investments and $6,357,000 related to depreciated investments.

The fund is managed by T. Rowe Price Associates, Inc. (Price Associates), a wholly owned subsidiary of T. Rowe Price Group, Inc. (Price Group). The investment management agreement between the fund and Price Associates 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 0.28% for assets in excess of $300 billion.

The fund’s group fee is determined by applying the group fee rate to the fund’s average daily net assets. At November 30, 2011, the effective annual group fee rate was 0.30%.

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 subaccounting and recordkeeping services for certain retirement accounts invested in the fund. For the six months ended November 30, 2011, expenses incurred pursuant to these service agreements were $62,000 for Price Associates; $306,000 for T. Rowe Price Services, Inc.; and $95,000 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 six months ended November 30, 2011, the fund was allocated $415,000 of Spectrum Funds’ expenses, of which $291,000 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 November 30, 2011, approximately 35% 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 Investment Funds), open-end management investment companies managed by Price Associates and considered affiliates of the fund. The T. Rowe Price Reserve Investment 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 Investment Funds pay no investment management fees.

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 website, sec.gov. The description of our proxy voting policies and procedures is also available on our website, troweprice.com. To access it, click on the words “Our Company” at the top of our corporate homepage. Then, when the next page appears, click on the words “Proxy Voting Policies” on the left side of the page.

Each fund’s most recent annual proxy voting record is available on our website and through the SEC’s website. To access it through our website, follow the directions above, then click on the words “Proxy Voting Records” on the right side of the Proxy Voting Policies page.

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 website (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.

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 is filed as an exhibit to the registrant’s annual Form N-CSR. No substantive amendments were approved or waivers were granted to this code of ethics during the registrant’s most recent fiscal half-year.

(a) 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.

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

(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.

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

(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	January 23, 2012

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	January 23, 2012


By	/s/ Gregory K. Hinkle
	Gregory K. Hinkle
	Principal Financial Officer

Date	January 23, 2012