485BPOS

Registration Nos. 033-01041/811-4441

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, DC 20549
FORM N-1A

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933 /X/

Post-Effective Amendment No. 39 /X/

and/or

REGISTRATION STATEMENT UNDER THE INVESTMENT COMPANY ACT OF 1940 /X/

Amendment No. 34 /X/

T. ROWE PRICE GNMA FUND

Exact Name of Registrant as Specified in Charter

100 East Pratt Street, Baltimore, Maryland 21202
Address of Principal Executive Offices

410-345-2000
Registrant’s Telephone Number, Including Area Code

David Oestreicher

100 East Pratt Street, Baltimore, Maryland 21202
Name and Address of Agent for Service

It is proposed that this filing will become effective (check appropriate box):

/X/Immediately upon filing pursuant to paragraph (b)

//On (date) pursuant to paragraph (b)

//60 days after filing pursuant to paragraph (a)(1)

//On (date) pursuant to paragraph (a)(1)

//75 days after filing pursuant to paragraph (a)(2)

//On (date) pursuant to paragraph (a)(2) of Rule 485

If appropriate, check the following box:

//This post-effective amendment designates a new effective date for a previously filed post-effective amendment.

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EXHIBITS

Exhibit	Exhibit No.
XBRL Instance Document	EX-101.INS
XBRL Taxonomy Extension Schema Document	EX-101.SCH
XBRL Taxonomy Extension Calculation Linkbase Document	EX-101.CAL
XBRL Taxonomy Extension Definition Linkbase Document	EX-101.DEF
XBRL Taxonomy Extension Labels Linkbase Document	EX-101.LAB
XBRL Taxonomy Extension Presentation Linkbase Document	EX-101.PRE

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Pursuant to the requirements of the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, the Registrant certifies that it meets all of the requirements for effectiveness of this Registration Statement pursuant to Rule 485(b) under the Securities Act of 1933 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, duly authorized, in the City of Baltimore, State of Maryland, this October 18, 2012.

T. ROWE PRICE GNMA FUND

/s/Edward C. Bernard

By:Edward C. Bernard

Chairman of the Board

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed below by the following persons in the capacities and on the dates indicated:

Signature	Title	Date
/s/Edward C. Bernard	Chairman of the Board	October 18, 2012
Edward C. Bernard	(Chief Executive Officer)
/s/Gregory K. Hinkle	Treasurer (Chief	October 18, 2012
Gregory K. Hinkle	Financial Officer)
*	Trustee	October 18, 2012
William R. Brody
*	Trustee	October 18, 2012
Jeremiah E. Casey
*	Trustee	October 18, 2012
Anthony W. Deering
*	Trustee	October 18, 2012
Donald W. Dick, Jr.
/s/Michael C. Gitlin	Trustee	October 18, 2012
Michael C. Gitlin
*	Trustee	October 18, 2012
Karen N. Horn
*	Trustee	October 18, 2012
Theo C. Rodgers
*	Trustee	October 18, 2012
John G. Schreiber

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*	Trustee	October 18, 2012
Mark. R. Tercek
*/s/David Oestreicher	Vice President and	October 18, 2012
David Oestreicher	Attorney-In-Fact

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T. ROWE PRICE BALANCED FUND, INC.

T. ROWE PRICE BLUE CHIP GROWTH FUND, INC.

T. ROWE PRICE CALIFORNIA TAX-FREE INCOME TRUST

T. ROWE PRICE CAPITAL APPRECIATION FUND

T. ROWE PRICE CAPITAL OPPORTUNITY FUND, INC.

T. ROWE PRICE CORPORATE INCOME FUND, INC.

T. ROWE PRICE DIVERSIFIED MID-CAP GROWTH FUND, INC.

T. ROWE PRICE DIVERSIFIED SMALL-CAP GROWTH FUND, INC.

T. ROWE PRICE DIVIDEND GROWTH FUND, INC.

T. ROWE PRICE EQUITY INCOME FUND

T. ROWE PRICE EQUITY SERIES, INC.

T. ROWE PRICE FINANCIAL SERVICES FUND, INC.

T. ROWE PRICE FIXED INCOME SERIES, INC.

T. ROWE PRICE FLOATING RATE FUND, INC.

T. ROWE PRICE GLOBAL REAL ESTATE FUND, INC.

T. ROWE PRICE GLOBAL TECHNOLOGY FUND, INC.

T. ROWE PRICE GNMA FUND

T. ROWE PRICE GROWTH & INCOME FUND, INC.

T. ROWE PRICE GROWTH STOCK FUND, INC.

T. ROWE PRICE HEALTH SCIENCES FUND, INC.

T. ROWE PRICE HIGH YIELD FUND, INC.

T. ROWE PRICE INDEX TRUST, INC.

T. ROWE PRICE INFLATION FOCUSED BOND FUND, INC.

T. ROWE PRICE INFLATION PROTECTED BOND FUND, INC.

T. ROWE PRICE INSTITUTIONAL EQUITY FUNDS, INC.

T. ROWE PRICE INSTITUTIONAL INCOME FUNDS, INC.

T. ROWE PRICE INSTITUTIONAL INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL INDEX FUND, INC.

T. ROWE PRICE INTERNATIONAL SERIES, INC.

T. ROWE PRICE MEDIA & TELECOMMUNICATIONS FUND, INC.

T. ROWE PRICE MID-CAP GROWTH FUND, INC.

T. ROWE PRICE MID-CAP VALUE FUND, INC.

T. ROWE PRICE MULTI-SECTOR ACCOUNT PORTFOLIOS, INC.

T. ROWE PRICE NEW AMERICA GROWTH FUND
T. ROWE PRICE NEW ERA FUND, INC.

T. ROWE PRICE NEW HORIZONS FUND, INC.

T. ROWE PRICE NEW INCOME FUND, INC.

T. ROWE PRICE PERSONAL STRATEGY FUNDS, INC.

T. ROWE PRICE PRIME RESERVE FUND, INC.

T. ROWE PRICE REAL ASSETS FUND, INC.

T. ROWE PRICE REAL ESTATE FUND, INC.

T. ROWE PRICE RESERVE INVESTMENT FUNDS, INC.

T. ROWE PRICE RETIREMENT FUNDS, INC.

T. ROWE PRICE SCIENCE & TECHNOLOGY FUND, INC.

T. ROWE PRICE SHORT-TERM BOND FUND, INC.

T. ROWE PRICE SMALL-CAP STOCK FUND, INC.

T. ROWE PRICE SMALL-CAP VALUE FUND, INC.

T. ROWE PRICE SPECTRUM FUND, INC.

T. ROWE PRICE STATE TAX-FREE INCOME TRUST

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T. ROWE PRICE STRATEGIC INCOME FUND, INC.

T. ROWE PRICE SUMMIT FUNDS, INC.

T. ROWE PRICE SUMMIT MUNICIPAL FUNDS, INC.

T. ROWE PRICE TAX-EFFICIENT FUNDS, INC.

T. ROWE PRICE TAX-EXEMPT MONEY FUND, INC.

T. ROWE PRICE TAX-FREE HIGH YIELD FUND, INC.

T. ROWE PRICE TAX-FREE INCOME FUND, INC.

T. ROWE PRICE TAX-FREE SHORT-INTERMEDIATE FUND, INC.

T. ROWE PRICE U.S. BOND ENHANCED INDEX FUND, INC.

T. ROWE PRICE U.S. LARGE-CAP CORE FUND, INC.

T. ROWE PRICE U.S. TREASURY FUNDS, INC.

T. ROWE PRICE VALUE FUND, INC.

POWER OF ATTORNEY

RESOLVED, that the Corporation does hereby constitute and authorize Edward C. Bernard, Margery K. Neale and David Oestreicher, and each of them individually, their true and lawful attorneys and agents to take any and all action and execute any and all instruments which said attorneys and agents may deem necessary or advisable to enable the Corporation/Trust to comply with the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, and any rules, regulations, orders or other requirements of the United States Securities and Exchange Commission thereunder, in connection with the registration under the Securities Act of 1933, as amended, of shares of the Corporation/Trust, to be offered by the Corporation/Trust, and the registration of the Corporation/Trust under the Investment Company Act of 1940, as amended, including specifically, but without limitation of the foregoing, power and authority to sign the name of the Corporation/Trust on its behalf, and to sign the names of each of such directors/trustees and officers on his behalf as such director/trustee or officer to any (i) Registration Statement on Form N-1A or N-14 of the Corporation/Trust filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended; (ii) Registration Statement on Form N-1A or N-14 of the Corporation/Trust under the Investment Company Act of 1940, as amended; (iii) amendment or supplement (including, but not limited to, Post-Effective Amendments adding additional series or classes of the Corporation/ Trust) to said Registration Statement; and (iv) instruments or documents filed or to be filed as a part of or in connection with such Registration Statement, including Articles Supplementary, Articles of Amendment, and other instruments with respect to the Articles of Incorporation or Master Trust Agreement of the Corporation/Trust.

IN WITNESS WHEREOF, the above named Corporations/Trusts have caused these presents to be signed and the same attested by its Secretary, each thereunto duly authorized by its Board of Directors/Trustees, and each of the undersigned has hereunto set his hand and seal as of the day set opposite his name.

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ALL CORPORATIONS/TRUSTS
/s/Edward C. Bernard Edward C. Bernard	Chairman of the Board (Principal Executive Officer) Director/Trustee	April 24, 2012
/s/Gregory K. Hinkle Gregory K. Hinkle	Treasurer (Principal Financial Officer)	April 24, 2012
/s/William R. Brody William R. Brody	Director/Trustee	April 24, 2012
/s/Jeremiah E. Casey Jeremiah E. Casey	Director/Trustee	April 24, 2012
/s/Anthony W. Deering Anthony W. Deering	Director/Trustee	April 24, 2012
/s/Donald W. Dick, Jr. Donald W. Dick, Jr.	Director/Trustee	April 24, 2012
/s/Karen N. Horn Karen N. Horn	Director/Trustee	April 24, 2012
/s/Theo C. Rodgers Theo C. Rodgers	Director/Trustee	April 24, 2012
/s/John G. Schreiber John G. Schreiber	Director/Trustee	April 24, 2012
/s/Mark R. Tercek Mark R. Tercek	Director/Trustee	April 24, 2012

(Signatures Continued)

Page 8

MICHAEL C. GITLIN, Director/Trustee

T. ROWE PRICE CALIFORNIA TAX-FREE INCOME TRUST

T. ROWE PRICE CORPORATE INCOME FUND, INC.

T. ROWE PRICE FIXED INCOME SERIES, INC.

T. ROWE PRICE GNMA FUND

T. ROWE PRICE FLOATING RATE FUND, INC.

T. ROWE PRICE HIGH YIELD FUND, INC.

T. ROWE PRICE INSTITUTIONAL INCOME FUNDS, INC.

T. ROWE PRICE INFLATION FOCUSED BOND FUND, INC.

T. ROWE PRICE INFLATION PROTECTED BOND FUND, INC.

T. ROWE PRICE NEW INCOME FUND, INC.

T. ROWE PRICE PRIME RESERVE FUND, INC.

T. ROWE PRICE RESERVE INVESTMENT FUNDS, INC.

T. ROWE PRICE SHORT-TERM BOND FUND, INC.

T. ROWE PRICE STATE TAX-FREE INCOME TRUST

T. ROWE PRICE STRATEGIC INCOME FUND, INC.

T. ROWE PRICE SUMMIT FUNDS, INC.

T. ROWE PRICE SUMMIT MUNICIPAL FUNDS, INC.

T. ROWE PRICE TAX-EXEMPT MONEY FUND, INC.

T. ROWE PRICE TAX-FREE HIGH YIELD FUND, INC.

T. ROWE PRICE TAX-FREE INCOME FUND, INC.

T. ROWE PRICE TAX-FREE SHORT-INTERMEDIATE FUND, INC.

T. ROWE PRICE U.S. BOND ENHANCED INDEX FUND, INC.

T. ROWE PRICE U.S. TREASURY FUNDS, INC.

MICHAEL C. GITLIN, Director and President

T. ROWE PRICE MULTI-SECTOR ACCOUNT PORTFOLIOS, INC.

/s/Michael C. Gitlin Michael C. Gitlin April 24, 2012

(Signatures Continued)

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JOHN H. LAPORTE, Director/Trustee

T. ROWE PRICE CAPITAL OPPORTUNITY FUND, INC.

T. ROWE PRICE DIVERSIFIED MID-CAP GROWTH FUND, INC.

T. ROWE PRICE EQUITY SERIES, INC.

T. ROWE PRICE NEW AMERICA GROWTH FUND

T. ROWE PRICE SCIENCE & TECHNOLOGY FUND, INC.

T. ROWE PRICE SMALL-CAP STOCK FUND, INC.

T. ROWE PRICE SMALL-CAP VALUE FUND, INC.

JOHN H. LAPORTE, Director and Vice President

T. ROWE PRICE DIVERSIFIED SMALL-CAP GROWTH FUND, INC.

T. ROWE PRICE HEALTH SCIENCES FUND, INC.

T. ROWE PRICE NEW HORIZONS FUND, INC.

/s/John H. Laporte John H. Laporte April 24, 2012

(Signatures Continued)

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BRIAN C. ROGERS, Director/Trustee

T. ROWE PRICE BALANCED FUND, INC.

T. ROWE PRICE BLUE CHIP GROWTH FUND, INC.

T. ROWE PRICE CAPITAL APPRECIATION FUND

T. ROWE PRICE DIVIDEND GROWTH FUND, INC.

T. ROWE PRICE FINANCIAL SERVICES FUND, INC.

T. ROWE PRICE GLOBAL REAL ESTATE FUND, INC.

T. ROWE PRICE GLOBAL TECHNOLOGY FUND, INC.

T. ROWE PRICE GROWTH & INCOME FUND, INC.

T. ROWE PRICE GROWTH STOCK FUND, INC.

T. ROWE INDEX TRUST, INC.

T. ROWE PRICE INSTITUTIONAL INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL INDEX FUND, INC.

T. ROWE PRICE INTERNATIONAL SERIES, INC.

T. ROWE PRICE MEDIA & TELECOMMUNICATIONS FUND, INC.

T. ROWE PRICE MID-CAP GROWTH FUND, INC.

T. ROWE PRICE MID-CAP VALUE FUND, INC.

T. ROWE PRICE NEW ERA FUND, INC.

T. ROWE PRICE REAL ASSETS FUND, INC.

T. ROWE PRICE REAL ESTATE FUND, INC.

T. ROWE PRICE TAX-EFFICIENT FUNDS, INC.

T. ROWE PRICE U.S. LARGE-CAP CORE FUND, INC.

BRIAN C. ROGERS, Director/Trustee and President

T. ROWE PRICE EQUITY INCOME FUND

T. ROWE PRICE INSTITUTIONAL EQUITY FUNDS, INC.

BRIAN C. ROGERS, Director/Trustee and Vice President

T. ROWE PRICE PERSONAL STRATEGY FUNDS, INC.

T. ROWE PRICE RETIREMENT FUNDS, INC.

T. ROWE PRICE SPECTRUM FUND, INC.

T. ROWE PRICE VALUE FUND, INC.

/s/Brian C. Rogers Brian C. Rogers April 24, 2012

(Signatures Continued)

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ATTEST:

/s/Patricia B. Lippert

Patricia B. Lippert, Secretary

Page 12

T. ROWE PRICE BALANCED FUND, INC.

T. ROWE PRICE BLUE CHIP GROWTH FUND, INC.

T. ROWE PRICE CAPITAL APPRECIATION FUND

T. ROWE PRICE CAPITAL OPPORTUNITY FUND, INC.

T. ROWE PRICE DIVERSIFIED MID-CAP GROWTH FUND, INC.

T. ROWE PRICE DIVERSIFIED SMALL-CAP GROWTH FUND, INC.

T. ROWE PRICE DIVIDEND GROWTH FUND, INC.

T. ROWE PRICE EQUITY INCOME FUND

T. ROWE PRICE EQUITY SERIES, INC.

T. ROWE PRICE FINANCIAL SERVICES FUND, INC.

T. ROWE PRICE GLOBAL REAL ESTATE FUND, INC.

T. ROWE PRICE GLOBAL TECHNOLOGY FUND, INC.

T. ROWE PRICE GROWTH & INCOME FUND, INC.

T. ROWE PRICE GROWTH STOCK FUND, INC.

T. ROWE PRICE HEALTH SCIENCES FUND, INC.

T. ROWE PRICE INDEX TRUST, INC.

T. ROWE PRICE INSTITUTIONAL EQUITY FUNDS, INC.

T. ROWE PRICE INSTITUTIONAL INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL FUNDS, INC.

T. ROWE PRICE INTERNATIONAL INDEX FUND, INC.

T. ROWE PRICE INTERNATIONAL SERIES, INC.

T. ROWE PRICE MEDIA & TELECOMMUNICATIONS FUND, INC.

T. ROWE PRICE MID-CAP GROWTH FUND, INC.

T. ROWE PRICE MID-CAP VALUE FUND, INC.

T. ROWE PRICE NEW AMERICA GROWTH FUND
T. ROWE PRICE NEW ERA FUND, INC.

T. ROWE PRICE NEW HORIZONS FUND, INC.

T. ROWE PRICE PERSONAL STRATEGY FUNDS, INC.

T. ROWE PRICE REAL ASSETS FUND, INC.

T. ROWE PRICE REAL ESTATE FUND, INC.

T. ROWE PRICE RETIREMENT FUNDS, INC.

T. ROWE PRICE SCIENCE & TECHNOLOGY FUND, INC.

T. ROWE PRICE SMALL-CAP STOCK FUND, INC.

T. ROWE PRICE SMALL-CAP VALUE FUND, INC.

T. ROWE PRICE SPECTRUM FUND, INC.

T. ROWE PRICE TAX-EFFICIENT FUNDS, INC.

T. ROWE PRICE U.S. LARGE-CAP CORE FUND, INC.

T. ROWE PRICE VALUE FUND, INC.

POWER OF ATTORNEY

RESOLVED, that the Corporation does hereby constitute and authorize Edward C. Bernard, Margery K. Neale and David Oestreicher, and each of them individually, their true and lawful attorneys and agents to take any and all action and execute any and all instruments which said attorneys and agents may deem necessary or advisable to enable the Corporation/Trust to comply with the Securities Act of 1933, as amended, and the Investment Company Act of 1940, as amended, and any rules, regulations, orders or other requirements of the United States Securities and Exchange Commission thereunder, in connection with the registration under the Securities Act of 1933, as amended, of shares of the Corporation/Trust, to be offered by the Corporation/Trust, and the registration of the Corporation/Trust under the Investment Company Act of 1940, as amended, including specifically, but without limitation of the foregoing, power and authority to sign the name of the Corporation/Trust on its behalf, and to sign

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the names of each of such directors/trustees and officers on his behalf as such director/trustee or officer to any (i) Registration Statement on Form N-1A or N-14 of the Corporation/Trust filed with the Securities and Exchange Commission under the Securities Act of 1933, as amended; (ii) Registration Statement on Form N-1A or N-14 of the Corporation/Trust under the Investment Company Act of 1940, as amended; (iii) amendment or supplement (including, but not limited to, Post-Effective Amendments adding additional series or classes of the Corporation/ Trust) to said Registration Statement; and (iv) instruments or documents filed or to be filed as a part of or in connection with such Registration Statement, including Articles Supplementary, Articles of Amendment, and other instruments with respect to the Articles of Incorporation or Master Trust Agreement of the Corporation/Trust.

IN WITNESS WHEREOF, the above named Corporations/Trusts have caused these presents to be signed and the same attested by its Secretary, each thereunto duly authorized by its Board of Directors/Trustees, and each of the undersigned has hereunto set his hand and seal as of the day set opposite his name.

/s/Robert J. Gerrard, Jr. Robert J. Gerrard, Jr.	Director/Trustee	May 2, 2012
/s/Cecilia E. Rouse Cecilia E. Rouse	Director/Trustee	May 2, 2012

ATTEST:

/s/Patricia B. Lippert

Patricia B. Lippert, Secretary

XML

Label	Element	Value
Risk/Return:	rr_RiskReturnAbstract
Registrant Name	dei_EntityRegistrantName	T. Rowe Price GNMA Fund
Prospectus Date	rr_ProspectusDate	Oct. 01, 2012
Document Creation Date	dei_DocumentCreationDate	Sep. 27, 2012

XML

Label

Element

Value

Risk/Return:

rr_RiskReturnAbstract

Registrant Name

dei_EntityRegistrantName

T. Rowe Price GNMA Fund

Prospectus Date

rr_ProspectusDate

Oct. 01, 2012

T. Rowe Price GNMA Fund

Risk/Return:

rr_RiskReturnAbstract

Risk/Return [Heading]

rr_RiskReturnHeading

T. Rowe Price

GNMA Fund

SUMMARY

Objective [Heading]

rr_ObjectiveHeading

Investment Objective

Objective, Primary [Text Block]

rr_ObjectivePrimaryTextBlock

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 Government National Mortgage Association securities backed by the full faith and credit of the U.S. government.

Expense [Heading]

rr_ExpenseHeading

Fees and Expenses

Expense Narrative [Text Block]

rr_ExpenseNarrativeTextBlock

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

Shareholder Fees Caption [Text]

rr_ShareholderFeesCaption

Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)

Operating Expenses Caption [Text]

rr_OperatingExpensesCaption

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

Portfolio Turnover [Heading]

rr_PortfolioTurnoverHeading

Portfolio Turnover

Portfolio Turnover [Text Block]

rr_PortfolioTurnoverTextBlock

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 344.3% of the average value of its portfolio.

Portfolio Turnover, Rate

rr_PortfolioTurnoverRate

344.30%

Expenses Not Correlated to Ratio Due to Acquired Fund Fees [Text]

rr_ExpensesNotCorrelatedToRatioDueToAcquiredFundFees

The figure shown under “Total annual fund operating expenses” does not match the “Ratio of expenses to average net assets” shown in the Financial Highlights table, as that figure does not include acquired fund fees and expenses.

Expense Example [Heading]

rr_ExpenseExampleHeading

Example

Expense Example Narrative [Text Block]

rr_ExpenseExampleNarrativeTextBlock

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

Strategy [Heading]

rr_StrategyHeading

Investments, Risks, and Performance

Principal Investment Strategies

Strategy Narrative [Text Block]

rr_StrategyNarrativeTextBlock

The fund will normally invest at least 80% of its total assets in mortgage-backed securities issued by the Government National Mortgage Association (GNMA), an agency of the U.S. Department of Housing and Urban Development. These securities represent “pools” of mortgage loans that are guaranteed either by the Federal Housing Administration or the Veterans Administration. Mortgage lenders pool individual home mortgages to back a certificate or bond, which entitle the holder to a proportionate share of the principal and interest payments that are made on the underlying pool of mortgage loans.

GNMA guarantees the timely payment of interest and principal on the securities it issues, a guarantee backed by the U.S. Treasury. The GNMA guarantee does not apply to the price of GNMA securities or the fund’s share price, both of which will fluctuate with market conditions.

Up to 20% of total assets can be invested in high-quality securities that are not backed by the full faith and credit of the U.S. government. These securities must have a credit rating of at least AA (or an equivalent rating) at the time of purchase by at least one of the major credit rating agencies or, if unrated, deemed to be of comparable quality by T. Rowe Price. Such securities may include, among others, mortgage-backed securities issued by government agencies (such as the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation) that are not backed by the full faith and credit of the U.S. government and mortgage-related securities issued by private banks and other non-governmental issuers.

There is no limit on the maturity of individual securities in the fund’s portfolio or on the fund’s overall weighted average maturity, which will vary and can be influenced by various factors such as the general level of interest rates, and principal prepayments of GNMA and other mortgage-backed securities.

In selecting securities, the portfolio manager may weigh the characteristics of various types of mortgage-backed securities and examine yield relationships in the context of the outlook for interest rates and the economy. For example, if interest rates seem likely to fall, the portfolio manager may purchase mortgage-backed securities expected to have below-average prepayment rates with longer maturities and allocate some assets to bonds or other securities that could appreciate in that environment.

The fund may purchase or sell mortgage-backed securities on a delayed delivery or forward commitment basis through the “to-be-announced” (TBA) market. With TBA transactions, the particular securities to be delivered are not identified at the trade date but the delivered securities must meet specified terms and standards. The fund would generally enter into TBA transactions with the intention of taking possession of the underlying mortgage-backed securities. However, in an effort to obtain underlying mortgage securities on more preferable terms or to enhance returns, the fund may extend the settlement by entering into “dollar roll” transactions in which the fund sells mortgage-backed securities and simultaneously agrees to purchase substantially similar securities on a future date. In addition, the fund uses interest rate futures and interest rate swaps primarily in an effort to manage its exposure to changes in interest rates or to adjust portfolio duration.

The fund may sell holdings for a variety of reasons, such as to adjust the portfolio’s average maturity or to shift assets into and out of higher-yielding securities.

Risk [Heading]

rr_RiskHeading

Principal Risks

Risk Narrative [Text Block]

rr_RiskNarrativeTextBlock

As with any mutual fund, there is no guarantee that the fund will achieve its objective. The fund’s share price fluctuates, which means you could lose money by investing in the fund. The principal risks of investing in this fund are summarized as follows:

Active management risk The fund is subject to the risk that the investment adviser’s judgments about the attractiveness, value, or potential appreciation of the fund’s investments may prove to be incorrect. If the securities selected and strategies employed by the fund fail to produce the intended results, the fund could underperform other funds with similar objectives and investment strategies.

Interest rate risk This is the risk that a rise in interest rates will cause the price of a fixed rate debt security to fall. Generally, securities with longer maturities and funds with longer weighted average maturities carry greater interest rate risk. The market tends to discount prices of mortgage-backed securities for prepayment risk when interest rates decline. As a result, prices of mortgage-backed securities typically do not rise as much as the prices of comparable bonds during periods of falling interest rates.

Prepayment risk This is the risk that during periods of falling interest rates, borrowers will refinance their mortgages before their maturity dates, leading to the prepayment of mortgage-backed securities held by the fund. The fund would lose potential price appreciation and may be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the fund’s income.

Extension risk This is the risk that during periods of rising interest rates, prepayments of the underlying mortgages will occur at a slower than expected rate, thereby lengthening the average life of the mortgage-backed securities and making them more volatile.

Credit risk This is the risk that an issuer of a debt security could suffer an adverse change in financial condition that results in a payment default, security downgrade, or inability to meet a financial obligation. The fund’s overall exposure to credit risk is relatively low because it invests significantly in higher rated securities and certain securities that are backed by the full faith and credit of the U.S. government or a federally sponsored agency. There is a relatively higher risk of default for U.S. agency issued securities that are not guaranteed by the U.S. government and an even higher risk of default for securities not backed by any government agency, although pooling mortgages helps to mitigate some of the credit risk.

Liquidity risk This is the risk that the fund may not be able to sell a holding in a timely manner at a desired price.

TBA/Dollar roll risk Although the securities that are delivered in TBA transactions must meet certain standards, there is a risk that the actual securities received by the fund may be less favorable than what was anticipated when entering into the transaction. TBA transactions also involve the risk that a counterparty will fail to deliver the security, exposing the fund to further losses. Whether or not the fund takes delivery of the securities at the termination date of a TBA transaction, it will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement. Finally, the fund’s portfolio turnover rate and transaction costs would be increased to the extent it enters into dollar roll transactions.

Derivatives risk The fund’s use of interest rate futures and interest rate swaps involves the risks that anticipated changes in interest rates, yield curves, or prepayment rates will not be accurately predicted, the possibility of regulatory developments that could negatively affect such instruments, and the potential for losses in excess of the fund’s initial investment. Interest rate swaps also involve the possible failure of a counterparty to perform in accordance with the terms of the swap agreement.

Risk Lose Money [Text]

rr_RiskLoseMoney

The fund’s share price fluctuates, which means you could lose money by investing in the fund.

Bar Chart and Performance Table [Heading]

rr_BarChartAndPerformanceTableHeading

Performance

Performance Narrative [Text Block]

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The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next and how fund performance compares with that of a comparable market index. The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.

The fund can also experience short-term performance swings, as shown by the best and worst calendar quarter returns during the years depicted.

Performance Information Illustrates Variability of Returns [Text]

rr_PerformanceInformationIllustratesVariabilityOfReturns

The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next and how fund performance compares with that of a comparable market index.

Performance Availability Phone [Text]

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1-800-225-5132

Performance Availability Website Address [Text]

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troweprice.com

Performance Past Does Not Indicate Future [Text]

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The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.

Bar Chart [Heading]

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GNMA Fund
Calendar Year Returns

Bar Chart Closing [Text Block]

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	Quarter Ended	Total Return
Best Quarter	6/30/02	3.56%
Worst Quarter	6/30/04	-1.13%

The fund’s return for the six months ended 6/30/12 was 1.89%.

Performance Table Heading

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Average Annual Total Returns

Periods ended
December 31, 2011

Performance Table Uses Highest Federal Rate

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After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes.

Performance Table Not Relevant to Tax Deferred

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After-tax returns shown are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as a 401(k) account or individual retirement account.

Performance Table Narrative

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In addition, the average annual total returns table shows hypothetical after-tax returns to suggest how taxes paid by a shareholder may influence returns. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as a 401(k) account or individual retirement account.

Performance Table Closing [Text Block]

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Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132.

T. Rowe Price GNMA Fund | T. Rowe Price GNMA Fund

Risk/Return:

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Maximum sales charge (load) imposed on purchases

rr_MaximumSalesChargeImposedOnPurchasesOverOfferingPrice

none

Maximum deferred sales charge (load)

rr_MaximumDeferredSalesChargeOverOfferingPrice

none

Redemption fee

rr_RedemptionFeeOverRedemption

none

Maximum account fee

rr_MaximumAccountFee

20

^[1]

Management fees

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0.45%

Distribution and service (12b-1) fees

rr_DistributionAndService12b1FeesOverAssets

none

Other expenses

rr_OtherExpensesOverAssets

0.15%

Acquired fund fees and expenses

rr_AcquiredFundFeesAndExpensesOverAssets

0.02%

Total annual fund operating expenses

rr_ExpensesOverAssets

0.62%

^[2]

1 year

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63

3 years

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199

5 years

rr_ExpenseExampleYear05

346

10 years

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774

2002

rr_AnnualReturn2002

9.03%

2003

rr_AnnualReturn2003

2.36%

2004

rr_AnnualReturn2004

3.80%

2005

rr_AnnualReturn2005

2.74%

2006

rr_AnnualReturn2006

3.86%

2007

rr_AnnualReturn2007

6.55%

2008

rr_AnnualReturn2008

5.62%

2009

rr_AnnualReturn2009

6.35%

2010

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6.49%

2011

rr_AnnualReturn2011

6.46%

Year to Date Return, Label

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The fund's return for the six months ended

Bar Chart, Year to Date Return, Date

rr_BarChartYearToDateReturnDate

Jun. 30, 2012

Bar Chart, Year to Date Return

rr_BarChartYearToDateReturn

1.89%

Highest Quarterly Return, Label

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Best Quarter

Highest Quarterly Return, Date

rr_BarChartHighestQuarterlyReturnDate

Jun. 30, 2002

Highest Quarterly Return

rr_BarChartHighestQuarterlyReturn

3.56%

Lowest Quarterly Return, Label

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Worst Quarter

Lowest Quarterly Return, Date

rr_BarChartLowestQuarterlyReturnDate

Jun. 30, 2004

Lowest Quarterly Return

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(1.13%)

1 Year

rr_AverageAnnualReturnYear01

6.46%

5 Years

rr_AverageAnnualReturnYear05

6.29%

10 Years

rr_AverageAnnualReturnYear10

5.31%

T. Rowe Price GNMA Fund | Returns after taxes on distributions | T. Rowe Price GNMA Fund

Risk/Return:

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1 Year

rr_AverageAnnualReturnYear01

4.92%

5 Years

rr_AverageAnnualReturnYear05

4.63%

10 Years

rr_AverageAnnualReturnYear10

3.83%

T. Rowe Price GNMA Fund | Returns after taxes on distributions and sale of fund shares | T. Rowe Price GNMA Fund

Risk/Return:

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1 Year

rr_AverageAnnualReturnYear01

4.21%

5 Years

rr_AverageAnnualReturnYear05

4.41%

10 Years

rr_AverageAnnualReturnYear10

3.74%

T. Rowe Price GNMA Fund | Barclays U.S. GNMA Index (reflects no deduction for fees, expenses, or taxes)

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

7.90%

5 Years

rr_AverageAnnualReturnYear05

6.95%

10 Years

rr_AverageAnnualReturnYear10

5.83%

T. Rowe Price GNMA Fund | Lipper GNMA Funds Average

Risk/Return:

rr_RiskReturnAbstract

1 Year

rr_AverageAnnualReturnYear01

6.62%

5 Years

rr_AverageAnnualReturnYear05

6.41%

10 Years

rr_AverageAnnualReturnYear10

5.18%

[1] Subject to certain exceptions, accounts with a balance of less than $10,000 are charged an annual $20 fee.

[2] The figure shown under "Total annual fund operating expenses" does not match the "Ratio of expenses to average net assets" shown in the Financial Highlights table, as that figure does not include acquired fund fees and expenses.

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T. Rowe Price GNMA Fund

T. Rowe Price

GNMA Fund

SUMMARY

Investment Objective

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 Government National Mortgage Association securities backed by the full faith and credit of the U.S. government.

Fees and Expenses

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

Fees and Expenses of the Fund

Shareholder fees (fees paid directly from your investment)

Shareholder Fees (USD $)		T. Rowe Price GNMA Fund
Maximum sales charge (load) imposed on purchases		none
Maximum deferred sales charge (load)		none
Redemption fee		none
Maximum account fee	[1]	20

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

Annual Fund Operating Expenses		T. Rowe Price GNMA Fund
Management fees		0.45%
Distribution and service (12b-1) fees		none
Other expenses		0.15%
Acquired fund fees and expenses		0.02%
Total annual fund operating expenses	[1]	0.62%

Example

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

Expense Example (USD $)	1 year	3 years	5 years	10 years
T. Rowe Price GNMA Fund	63	199	346	774

Portfolio Turnover

The fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the fund’s performance. During the most recent fiscal year, the fund’s portfolio turnover rate was 344.3% of the average value of its portfolio.

Investments, Risks, and Performance

Principal Investment Strategies

The fund will normally invest at least 80% of its total assets in mortgage-backed securities issued by the Government National Mortgage Association (GNMA), an agency of the U.S. Department of Housing and Urban Development. These securities represent “pools” of mortgage loans that are guaranteed either by the Federal Housing Administration or the Veterans Administration. Mortgage lenders pool individual home mortgages to back a certificate or bond, which entitle the holder to a proportionate share of the principal and interest payments that are made on the underlying pool of mortgage loans.

GNMA guarantees the timely payment of interest and principal on the securities it issues, a guarantee backed by the U.S. Treasury. The GNMA guarantee does not apply to the price of GNMA securities or the fund’s share price, both of which will fluctuate with market conditions.

Up to 20% of total assets can be invested in high-quality securities that are not backed by the full faith and credit of the U.S. government. These securities must have a credit rating of at least AA (or an equivalent rating) at the time of purchase by at least one of the major credit rating agencies or, if unrated, deemed to be of comparable quality by T. Rowe Price. Such securities may include, among others, mortgage-backed securities issued by government agencies (such as the Federal National Mortgage Association and the Federal Home Loan Mortgage Corporation) that are not backed by the full faith and credit of the U.S. government and mortgage-related securities issued by private banks and other non-governmental issuers.

There is no limit on the maturity of individual securities in the fund’s portfolio or on the fund’s overall weighted average maturity, which will vary and can be influenced by various factors such as the general level of interest rates, and principal prepayments of GNMA and other mortgage-backed securities.

In selecting securities, the portfolio manager may weigh the characteristics of various types of mortgage-backed securities and examine yield relationships in the context of the outlook for interest rates and the economy. For example, if interest rates seem likely to fall, the portfolio manager may purchase mortgage-backed securities expected to have below-average prepayment rates with longer maturities and allocate some assets to bonds or other securities that could appreciate in that environment.

The fund may purchase or sell mortgage-backed securities on a delayed delivery or forward commitment basis through the “to-be-announced” (TBA) market. With TBA transactions, the particular securities to be delivered are not identified at the trade date but the delivered securities must meet specified terms and standards. The fund would generally enter into TBA transactions with the intention of taking possession of the underlying mortgage-backed securities. However, in an effort to obtain underlying mortgage securities on more preferable terms or to enhance returns, the fund may extend the settlement by entering into “dollar roll” transactions in which the fund sells mortgage-backed securities and simultaneously agrees to purchase substantially similar securities on a future date. In addition, the fund uses interest rate futures and interest rate swaps primarily in an effort to manage its exposure to changes in interest rates or to adjust portfolio duration.

The fund may sell holdings for a variety of reasons, such as to adjust the portfolio’s average maturity or to shift assets into and out of higher-yielding securities.

Principal Risks

As with any mutual fund, there is no guarantee that the fund will achieve its objective. The fund’s share price fluctuates, which means you could lose money by investing in the fund. The principal risks of investing in this fund are summarized as follows:

Active management risk The fund is subject to the risk that the investment adviser’s judgments about the attractiveness, value, or potential appreciation of the fund’s investments may prove to be incorrect. If the securities selected and strategies employed by the fund fail to produce the intended results, the fund could underperform other funds with similar objectives and investment strategies.

Interest rate risk This is the risk that a rise in interest rates will cause the price of a fixed rate debt security to fall. Generally, securities with longer maturities and funds with longer weighted average maturities carry greater interest rate risk. The market tends to discount prices of mortgage-backed securities for prepayment risk when interest rates decline. As a result, prices of mortgage-backed securities typically do not rise as much as the prices of comparable bonds during periods of falling interest rates.

Prepayment risk This is the risk that during periods of falling interest rates, borrowers will refinance their mortgages before their maturity dates, leading to the prepayment of mortgage-backed securities held by the fund. The fund would lose potential price appreciation and may be forced to reinvest the unanticipated proceeds at lower interest rates, resulting in a decline in the fund’s income.

Extension risk This is the risk that during periods of rising interest rates, prepayments of the underlying mortgages will occur at a slower than expected rate, thereby lengthening the average life of the mortgage-backed securities and making them more volatile.

Credit risk This is the risk that an issuer of a debt security could suffer an adverse change in financial condition that results in a payment default, security downgrade, or inability to meet a financial obligation. The fund’s overall exposure to credit risk is relatively low because it invests significantly in higher rated securities and certain securities that are backed by the full faith and credit of the U.S. government or a federally sponsored agency. There is a relatively higher risk of default for U.S. agency issued securities that are not guaranteed by the U.S. government and an even higher risk of default for securities not backed by any government agency, although pooling mortgages helps to mitigate some of the credit risk.

Liquidity risk This is the risk that the fund may not be able to sell a holding in a timely manner at a desired price.

TBA/Dollar roll risk Although the securities that are delivered in TBA transactions must meet certain standards, there is a risk that the actual securities received by the fund may be less favorable than what was anticipated when entering into the transaction. TBA transactions also involve the risk that a counterparty will fail to deliver the security, exposing the fund to further losses. Whether or not the fund takes delivery of the securities at the termination date of a TBA transaction, it will nonetheless be exposed to changes in the value of the underlying investments during the term of the agreement. Finally, the fund’s portfolio turnover rate and transaction costs would be increased to the extent it enters into dollar roll transactions.

Derivatives risk The fund’s use of interest rate futures and interest rate swaps involves the risks that anticipated changes in interest rates, yield curves, or prepayment rates will not be accurately predicted, the possibility of regulatory developments that could negatively affect such instruments, and the potential for losses in excess of the fund’s initial investment. Interest rate swaps also involve the possible failure of a counterparty to perform in accordance with the terms of the swap agreement.

Performance

The bar chart showing calendar year returns and the average annual total returns table indicate risk by illustrating how much returns can differ from one year to the next and how fund performance compares with that of a comparable market index. The fund’s past performance (before and after taxes) is not necessarily an indication of future performance.

The fund can also experience short-term performance swings, as shown by the best and worst calendar quarter returns during the years depicted.

GNMA Fund
Calendar Year Returns

	Quarter Ended	Total Return
Best Quarter	6/30/02	3.56%
Worst Quarter	6/30/04	-1.13%

The fund’s return for the six months ended 6/30/12 was 1.89%.

In addition, the average annual total returns table shows hypothetical after-tax returns to suggest how taxes paid by a shareholder may influence returns. After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their fund shares through tax-deferred arrangements, such as a 401(k) account or individual retirement account.

Average Annual Total Returns

Periods ended
December 31, 2011

Average Annual Total Returns	1 Year	5 Years	10 Years
T. Rowe Price GNMA Fund	6.46%	6.29%	5.31%
T. Rowe Price GNMA Fund Returns after taxes on distributions	4.92%	4.63%	3.83%
T. Rowe Price GNMA Fund Returns after taxes on distributions and sale of fund shares	4.21%	4.41%	3.74%
T. Rowe Price GNMA Fund Barclays U.S. GNMA Index (reflects no deduction for fees, expenses, or taxes)	7.90%	6.95%	5.83%
T. Rowe Price GNMA Fund Lipper GNMA Funds Average	6.62%	6.41%	5.18%

Updated performance information is available through troweprice.com or may be obtained by calling 1-800-225-5132.

[1] Subject to certain exceptions, accounts with a balance of less than $10,000 are charged an annual $20 fee.

[1] The figure shown under "Total annual fund operating expenses" does not match the "Ratio of expenses to average net assets" shown in the Financial Highlights table, as that figure does not include acquired fund fees and expenses.

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Document and Entity Information	12 Months Ended
	Oct. 01, 2012
Risk/Return:
Document Type	485BPOS
Document Period End Date	May 31, 2012
Registrant Name	T. Rowe Price GNMA Fund
Central Index Key	0000779785
Amendment Flag	false
Document Creation Date	Sep. 27, 2012
Document Effective Date	Oct. 01, 2012
Prospectus Date	Oct. 01, 2012