November 3, 2006

Supplement

SUPPLEMENT DATED NOVEMBER 3, 2006 TO THE PROSPECTUS OF
MORGAN STANLEY U.S. GOVERNMENT SECURITIES TRUST
Dated April 28, 2006

The second paragraph in the section of the Fund's Prospectus titled ‘‘Principal Investment Strategies’’ is hereby deleted and replaced with the following:

The U.S. Government securities (including zero coupon securities) that the Fund may purchase include:

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U.S. Treasury bills, notes and bonds, all of which are direct obligations of the U.S. Government.

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Securities (including mortgage-backed securities) issued by agencies and instrumentalities of the U.S. Government which are backed by the full faith and credit of the United States. Among the agencies and instrumentalities issuing these obligations are the Government National Mortgage Association and the Federal Housing Administration.

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Securities (including mortgage-backed securities) issued by agencies and instrumentalities which are not backed by the full faith and credit of the United States, but whose issuing agency or instrumentality has the right to borrow, to meet its obligations, from the U.S. Treasury. Among these agencies and instrumentalities are the Federal National Mortgage Association (‘‘Fannie Mae’’) and the Federal Home Loan Mortgage Corporation (‘‘Freddie Mac’’).

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Securities issued by agencies and instrumentalities which are backed solely by the credit of the issuing agency or instrumentality. Among these agencies and instrumentalities are the Federal Farm Credit System and the Federal Home Loan Banks.

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Securities supported by the U.S. Government in some other way, such as the discretionary authority of the U.S. Government to purchase certain obligations of the agency or instrumentality.

The following paragraph is hereby added at the end of the section of the Fund's Prospectus titled ‘‘Principal Risks — U.S. Government Securities’’:

With respect to the U.S. Government securities which are not backed by the full faith and credit of the U.S. Government, there is the risk that the U.S. Government will not provide financial support to such U.S. Government agencies, instrumentalities or sponsored enterprises if it is not obligated to do so by law. Certain U.S. Government securities purchased by the Fund, such as those issued by Fannie Mae and Freddie Mac, are not backed by the full faith and credit of the United States. The maximum potential liability of the issuers of some U.S. Government securities held by the Fund may greatly exceed their current resources, including their legal right to support from the U.S. Treasury. It is possible that these issuers will not have the funds to meet their payment obligations in the future.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE.

USGSPT1 11/06

November 3, 2006

Supplement

SUPPLEMENT DATED NOVEMBER 3, 2006 TO THE STATEMENT OF ADDITIONAL INFORMATION OF
MORGAN STANLEY U.S. GOVERNMENT SECURITIES TRUST
Dated April 28, 2006

The disclosure in the section of the Fund's Statement of Additional Information entitled ‘‘II. Description of the Fund and Its Investments and Risks — C. Fund Policies/Investment Restrictions’’ is hereby deleted and replaced with the following:

C. Fund Policies/Investment Restrictions

The investment objective, policies and restrictions listed below have been adopted by the Fund as fundamental policies. Under the Investment Company Act, a fundamental policy may not be changed without the vote of a majority of the outstanding voting securities of the Fund. The Investment Company Act defines a majority as the lesser of (a) 67% or more of the shares present at a meeting of shareholders, if the holders of 50% of the outstanding shares of the Fund are present or represented by proxy, or (b) more than 50% of the outstanding shares of the Fund. For purposes of the following restrictions: (i) all percentage limitations apply immediately after a purchase or initial investment; except in the case of borrowing and investments in illiquid securities; and (ii) any subsequent change in any applicable percentage resulting from market fluctuations or other changes in total or net assets does not require elimination of any security from the portfolio, except in the case of borrowing and investments in illiquid securities.

The Fund will:

Seek high current income consistent with safety of principal.

The Fund may not:

Invest 25% or more of the value of its total assets in securities of issuers of any one industry. This restriction does not apply to bank obligations or obligations issued or guaranteed by the U.S. Government, its agencies or instrumentalities.

Invest in a manner inconsistent with its classification as a ‘‘diversified company’’ as provided by (i) the Investment Company Act, as amended from time to time, (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time, or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Borrow money, except the Fund may borrow money to the extent permitted by (i) the Investment Company Act, as amended from time to time, (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time, or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Make loans of money or property to any person, except (a) to the extent that securities or interests in which the Fund may invest are considered to be loans, (b) through the loan of portfolio securities, (c) by engaging in repurchase agreements or (d) as may otherwise be permitted by (i) the Investment Company Act, as amended from time to time, (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time, or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Purchase or sell physical commodities unless acquired as a result of ownership of securities or other instruments; provided that this restriction shall not prohibit the Fund from purchasing or selling options, futures contracts and related options thereon, forward contracts, swaps, caps, floors, collars and any other financial instruments or from investing in securities or other instruments backed by physical commodities or as otherwise permitted by (i) the Investment Company Act, as amended from time to time, (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time, or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Issue senior securities, except the Fund may issue senior securities to the extent permitted by (i) the Investment Company Act, as amended from time to time, (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time, or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Underwrite the securities of other issuers.

Purchase or sell real estate or interests therein (including limited partnership interests), although the Fund may purchase securities of issuers which engage in real estate operations and securities secured by real estate or interests therein.

In addition, as non-fundamental policies (which may be changed with Board approval and without shareholder vote), the Fund may not:

Make short sales of securities, except short sales against the box.

Invest its assets in the securities of any investment company except as may be permitted by (i) the Investment Company Act, as amended from time to time; (ii) the rules and regulations promulgated by the SEC under the Investment Company Act, as amended from time to time; or (iii) an exemption or other relief applicable to the Fund from the provisions of the Investment Company Act, as amended from time to time.

Invest more than 15% of its net assets on such other amount as may be permitted by SEC guidelines in illiquid securities, including restricted securities.

Invest in other investment companies in reliance on Sections 12(d)(1)(F), 12(d)(1)(G) or 12(d)(1)(J) of the Investment Company Act.

Notwithstanding any other investment policy or restriction, the Fund may seek to achieve its investment objective by investing all or substantially all of its assets in another investment company having substantially the same investment objective and policies as the Fund.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE.