MORGAN STANLEY DEAN WITTER US GOVERNMENT SECURITIES TRUST, 497, 1998-08-24

MORGAN STANLEY DEAN WITTER US GOVERNMENT SECURITIES TRUST
497, 1998-08-24

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<PAGE>
MORGAN STANLEY DEAN WITTER
U.S. GOVERNMENT SECURITIES TRUST
PROSPECTUS--APRIL 17, 1998
AS REVISED AUGUST 14, 1998

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MORGAN STANLEY DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST (THE "FUND") IS AN
OPEN-END DIVERSIFIED MANAGEMENT INVESTMENT COMPANY WHOSE INVESTMENT OBJECTIVE IS
HIGH CURRENT INCOME CONSISTENT WITH SAFETY OF PRINCIPAL. THE FUND OFFERS A
CONVENIENT AND ECONOMICAL WAY FOR PERSONS TO INVEST IN A PROFESSIONALLY MANAGED
DIVERSIFIED PORTFOLIO OF OBLIGATIONS ISSUED OR GUARANTEED BY THE U.S. GOVERNMENT
OR ITS INSTRUMENTALITIES. ALL SUCH OBLIGATIONS ARE BACKED BY THE FULL FAITH AND
CREDIT OF THE UNITED STATES. NO ASSURANCE CAN BE GIVEN THAT THE FUND'S OBJECTIVE
WILL BE REALIZED. SHARES OF THE FUND ARE NOT SPONSORED, GUARANTEED, ENDORSED OR
INSURED BY THE U.S. GOVERNMENT OR ANY AGENCY THEREOF.

The Fund offers four classes of shares (each, a "Class"), each with a different
combination of sales charges, ongoing fees and other features. The different
distribution arrangements permit an investor to choose the method of purchasing
shares that the investor believes is most beneficial given the amount of the
purchase, the length of time the investor expects to hold the shares and other
relevant circumstances. (See "Purchase of Fund Shares--Alternative Purchase
Arrangements.")

This Prospectus sets forth concisely the information you should know before
investing in the Fund. It should be read and retained for future reference.
Additional information about the Fund is contained in the Statement of
Additional Information, dated April 17, 1998, which has been filed with the
Securities and Exchange Commission, and which is available at no charge upon
request of the Fund at the address or telephone numbers listed on this page. The
Statement of Additional Information is incorporated herein by reference.

<TABLE>
<CAPTION>
TABLE OF CONTENTS

<S> <C>
Prospectus Summary................................ 2

Summary of Fund Expenses.......................... 4

Financial Highlights.............................. 5

The Fund and its Management....................... 8

Investment Objective and Policies................. 8

Risk Considerations............................. 10

Purchase of Fund Shares........................... 12

Shareholder Services.............................. 20

Redemptions and Repurchases....................... 23

Dividends, Distributions and Taxes................ 23

Performance Information........................... 24

Additional Information............................ 25
</TABLE>

SHARES OF THE FUND ARE NOT DEPOSITS OR OBLIGATIONS OF, OR GUARANTEED OR ENDORSED
BY, ANY BANK, AND THE SHARES ARE NOT FEDERALLY INSURED BY THE FEDERAL DEPOSIT
INSURANCE CORPORATION, THE FEDERAL RESERVE BOARD, OR ANY OTHER AGENCY.

MORGAN STANLEY DEAN WITTER
U.S. GOVERNMENT SECURITIES TRUST
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048
(212) 392-2550 or (800) 869-NEWS (toll-free)

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THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE SECURITIES
AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION PASSED UPON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

MORGAN STANLEY DEAN WITTER DISTRIBUTORS INC., DISTRIBUTOR
<PAGE>
PROSPECTUS SUMMARY
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<TABLE>
<S> <C>
THE FUND The Fund is organized as a Trust, commonly known as a Massachusetts business trust, and
is an open-end diversified management investment company investing in obligations issued
or guaranteed by the U.S. Government.
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SHARES OFFERED Shares of beneficial interest with $0.01 par value (see page 25). The Fund offers four
Classes of shares, each with a different combination of sales charges, ongoing fees and
other features (see pages 12-20).
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MINIMUM The minimum initial investment for each Class is $1,000 ($100 if the account is opened
PURCHASE through
EasyInvest-SM-). Class D shares are only available to persons investing $5 million ($25
million for certain qualified plans) or more and to certain other limited categories of
investors. For the purpose of meeting the minimum $5 million (or $25 million) investment
for Class D shares, and subject to the $1,000 minimum initial investment for each Class
of the Fund, an investor's existing holdings of Class A shares and shares of funds for
which Morgan Stanley Dean Witter Advisors Inc. serves as investment manager ("Morgan
Stanley Dean Witter Funds") that are sold with a front-end sales charge, and concurrent
investments in Class D shares of the Fund and other Morgan Stanley Dean Witter Funds
that are multiple class funds, will be aggregated. The minimum subsequent investment is
$100 (see page 12).
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INVESTMENT The investment objective of the Fund is high current income consistent with safety of
OBJECTIVE principal.
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INVESTMENT Morgan Stanley Dean Witter Advisors Inc., the Investment Manager of the Fund, and its
MANAGER wholly-owned subsidiary, Morgan Stanley Dean Witter Services Company Inc., serve in
various investment management, advisory, management and administrative capacities to 102
investment companies and other portfolios with assets of approximately $115.9 billion at
July 31, 1998 (see page 8).
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MANAGEMENT FEE The Investment Manager receives a monthly fee at the annual rate of 0.50% (1/2 of 1%) of
daily net assets, scaled down on assets over $1 billion. The fee should not be compared
with fees paid by other investment companies without also considering applicable sales
loads and distribution fees, including those noted below (see page 8).
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DISTRIBUTOR Morgan Stanley Dean Witter Distributors Inc. (the "Distributor"). The Fund has adopted a
AND distribution plan pursuant to Rule 12b-1 under the Investment Company Act (the "12b-1
DISTRIBUTION Plan") with respect to the distribution fees paid by the Class A, Class B and Class C
FEE shares of the Fund to the Distributor. The entire 12b-1 fee payable by Class A and a
portion of the 12b-1 fee payable by each of Class B and Class C equal to 0.20% of the
average daily net assets of Class B and 0.25% of the average daily net assets of Class C
are currently each characterized as a service fee within the meaning of the National
Association of Securities Dealers, Inc. guidelines. The remaining portion of the 12b-1
fee, if any, is characterized as an asset-based sales charge (see pages 12 and 19).
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ALTERNATIVE Four classes of shares are offered:
PURCHASE - Class A shares are offered with a front-end sales charge, starting at 4.25% and
ARRANGEMENTS reduced for larger purchases. Investments of $1 million or more (and investments by
certain other limited categories of investors) are not subject to any sales charge at
the time of purchase but a contingent deferred sales charge ("CDSC") of 1.0% may be
imposed on redemptions within one year of purchase. The Fund is authorized to reimburse
the Distributor for specific expenses incurred in promoting the distribution of the
Fund's Class A shares and servicing shareholder accounts pursuant to the Fund's 12b-1
Plan. Reimbursement may in no event exceed an amount equal to payments at an annual rate
of 0.25% of average daily net assets of the Class (see pages 12, 15 and 19).

- Class B shares are offered without a front-end sales charge, but will in most cases be
subject to a CDSC (scaled down from 5.0% to 1.0%) if redeemed within six years after
purchase. The CDSC will be imposed on any redemption of shares if after such redemption
the aggregate current value of a Class B account with the Fund falls below the aggregate
amount of the investor's purchase payments made during the six years preceding the
redemption. A different CDSC schedule applies to investments by certain qualified plans.
Class B shares are also subject to a 12b-1 fee assessed at the annual rate of 0.75%
(0.65% on amounts over $10 billion) of the lesser of: (a) the average daily net sales of
the Fund's Class B shares or (b) the average daily net assets of Class B. All shares of
the Fund held prior to July 28, 1997 (other than the shares held by certain employee
benefit plans established by Dean Witter Reynolds Inc. and its affiliate, SPS
Transaction Services, Inc.) have been designated Class B shares. Shares held by those
employee benefit plans prior to July 28, 1997 have been designated Class D shares.
Shares held before May 1, 1997 that have been designated Class B shares will convert to
Class A shares in May, 2007. In all other instances, Class B shares convert to Class A
shares approximately ten years after the date of the original purchase (see pages 12, 17
and 19).
</TABLE>

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2
<PAGE>
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<TABLE>
<S> <C>
- Class C shares are offered without a front-end sales charge, but will in most cases be
subject to a CDSC of 1.0% if redeemed within one year after purchase. The Fund is
authorized to reimburse the Distributor for specific expenses incurred in promoting the
distribution of the Fund's Class C shares and servicing shareholder accounts pursuant to
the Fund's 12b-1 Plan. Reimbursement may in no event exceed an amount equal to payments
at an annual rate of 0.75% of average daily net assets of the Class (see pages 12, 18
and 20).

- Class D shares are offered only to investors meeting an initial investment minimum of
$5 million ($25 million for certain qualified plans) and to certain other limited
categories of investors. Class D shares are offered without a front-end sales charge or
CDSC and are not subject to any 12b-1 fee (see pages 12, 18 and 20).
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DIVIDENDS AND Dividends from net investment income are declared daily and paid monthly and
CAPITAL GAINS distributions from net capital gains, if any, are paid at least once per year. The Fund
DISTRIBUTIONS may, however, determine to retain all or part of any net long-term capital gains in any
year for reinvestment. Dividends and capital gains distributions paid on shares of a
Class are automatically reinvested in additional shares of the same Class at net asset
value unless the shareholder elects to receive cash. Shares acquired by dividend and
distribution reinvestment will not be subject to any sales charge or CDSC (see pages 20
and 23).
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REDEMPTION Shares are redeemable by the shareholder at net asset value less any applicable CDSC on
Class A, Class B or Class C shares. An account may be involuntarily redeemed if the
total value of the account is less than $100 or, if the account was opened through
EasyInvest-SM-, if after twelve months the shareholder has invested less than $1,000 in
the account (see page 23).
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RISKS The Fund invests only in obligations issued or guaranteed by the U.S. Government which
are subject to minimal risk of loss of income and principal. It may engage in the
purchase of such securities on a when-issued basis. The value of the Fund's portfolio
securities, and therefore the Fund's net asset value per share, may increase or decrease
due to various factors, principally changes in prevailing interest rates. Generally, a
rise in interest rates will result in a decrease in the Fund's net asset value per
share, while a drop in interest rates will result in an increase in the Fund's net asset
value per share. In addition, the average life of certain of the securities held in the
Fund's portfolio (i.e., GNMA Certificates) may be shortened by prepayments or
refinancings of the mortgage pools underlying such securities. Such prepayments may have
an impact on dividends paid by the Fund (see pages 8-12).
</TABLE>

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THE ABOVE IS QUALIFIED IN ITS ENTIRETY BY THE DETAILED INFORMATION APPEARING
ELSEWHERE IN THIS PROSPECTUS AND IN THE STATEMENT OF
ADDITIONAL INFORMATION.

3
<PAGE>
SUMMARY OF FUND EXPENSES
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The following table illustrates all expenses and fees that a shareholder of the
Fund will incur. The expenses and fees set forth in the table are based on the
expenses and fees for the fiscal year ended December 31, 1997.

<TABLE>
<CAPTION>
CLASS A CLASS B CLASS C CLASS D
--------- ------- --------- -------
<S> <C> <C> <C> <C>
SHAREHOLDER TRANSACTION EXPENSES
Maximum Sales Charge Imposed on Purchases (as a percentage of offering price)... 4.25%(1) None None None
Sales Charge Imposed on Dividend Reinvestments.................................. None None None None
Maximum Contingent Deferred Sales Charge (as a percentage of original purchase
price or redemption proceeds).................................................. None(2) 5.00%(3) 1.00%(4) None
Redemption Fees................................................................. None None None None
Exchange Fee.................................................................... None None None None

ANNUAL FUND OPERATING EXPENSES (AS A PERCENTAGE OF AVERAGE NET ASSETS)
Management Fees................................................................. 0.43% 0.43% 0.43% 0.43%
12b-1 Fees (5) (6).............................................................. 0.25% 0.75% 0.75% None
Other Expenses.................................................................. 0.08% 0.08% 0.08% 0.08%
Total Fund Operating Expenses (7)............................................... 0.76% 1.26% 1.26% 0.51%
</TABLE>

- ---------------
(1) REDUCED FOR PURCHASES OF $25,000 AND OVER (SEE "PURCHASE OF FUND
SHARES--INITIAL SALES CHARGE ALTERNATIVE--CLASS A SHARES").
(2) INVESTMENTS THAT ARE NOT SUBJECT TO ANY SALES CHARGE AT THE TIME OF PURCHASE
ARE SUBJECT TO A CDSC OF 1.00% THAT WILL BE IMPOSED ON REDEMPTIONS MADE
WITHIN ONE YEAR AFTER PURCHASE, EXCEPT FOR CERTAIN SPECIFIC CIRCUMSTANCES
(SEE "PURCHASE OF FUND SHARES--INITIAL SALES CHARGE ALTERNATIVE--CLASS A
SHARES").
(3) THE CDSC IS SCALED DOWN TO 1.00% DURING THE SIXTH YEAR, REACHING ZERO
THEREAFTER.
(4) ONLY APPLICABLE TO REDEMPTIONS MADE WITHIN ONE YEAR AFTER PURCHASE (SEE
"PURCHASE OF FUND SHARES--LEVEL LOAD ALTERNATIVE--CLASS C SHARES").
(5) THE 12b-1 FEE IS ACCRUED DAILY AND PAYABLE MONTHLY. THE ENTIRE 12b-1 FEE
PAYABLE BY CLASS A AND A PORTION OF THE 12b-1 FEE PAYABLE BY EACH OF CLASS B
AND CLASS C EQUAL TO 0.20% OF THE AVERAGE DAILY NET ASSETS OF CLASS B AND
0.25% OF THE AVERAGE DAILY NET ASSETS OF CLASS C ARE CURRENTLY EACH
CHARACTERIZED AS A SERVICE FEE WITHIN THE MEANING OF NATIONAL ASSOCIATION OF
SECURITIES DEALERS, INC. ("NASD") GUIDELINES AND ARE PAYMENTS MADE FOR
PERSONAL SERVICE AND/OR MAINTENANCE OF SHAREHOLDER ACCOUNTS. THE REMAINDER
OF THE 12b-1 FEE, IF ANY, IS AN ASSET-BASED SALES CHARGE, AND IS A
DISTRIBUTION FEE PAID TO THE DISTRIBUTOR TO COMPENSATE IT FOR THE SERVICES
PROVIDED AND THE EXPENSES BORNE BY THE DISTRIBUTOR AND OTHERS IN THE
DISTRIBUTION OF THE FUND'S SHARES (SEE "PURCHASE OF FUND SHARES--PLAN OF
DISTRIBUTION").
(6) UPON CONVERSION OF CLASS B SHARES TO CLASS A SHARES, SUCH SHARES WILL BE
SUBJECT TO THE LOWER 12b-1 FEE APPLICABLE TO CLASS A SHARES. NO SALES CHARGE
IS IMPOSED AT THE TIME OF CONVERSION OF CLASS B SHARES TO CLASS A SHARES.
CLASS C SHARES DO NOT HAVE A CONVERSION FEATURE AND, THEREFORE, ARE SUBJECT
TO AN ONGOING 0.75% DISTRIBUTION FEE (SEE "PURCHASE OF FUND
SHARES--ALTERNATIVE PURCHASE ARRANGEMENTS").
(7) THERE WERE NO OUTSTANDING SHARES OF CLASS A, CLASS C OR CLASS D PRIOR TO
JULY 28, 1997. ACCORDINGLY, "TOTAL FUND OPERATING EXPENSES," AS SHOWN ABOVE
WITH RESPECT TO THOSE CLASSES, ARE ESTIMATES BASED UPON THE SUM OF 12b-1
FEES, MANAGEMENT FEES AND ESTIMATED "OTHER EXPENSES."

<TABLE>
<CAPTION>
EXAMPLES 1 YEAR 3 YEARS 5 YEARS 10 YEARS
------ ------- ------- --------
<S> <C> <C> <C> <C>
You would pay the following expenses on a $1,000
investment assuming (1) a 5% annual return and
(2) redemption at the end of each time period:
Class A....................................... $50 $66 $83 $133
Class B....................................... $63 $70 $89 $152
Class C....................................... $23 $40 $69 $152
Class D....................................... $ 5 $16 $29 $ 64

You would pay the following expenses on the same
$1,000 investment assuming no redemption at the
end of the period:
Class A....................................... $50 $66 $83 $133
Class B....................................... $13 $40 $69 $152
Class C....................................... $13 $40 $69 $152
Class D....................................... $ 5 $16 $29 $ 64
</TABLE>

THE ABOVE EXAMPLES SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE
EXPENSES OR PERFORMANCE. ACTUAL EXPENSES OF EACH CLASS MAY BE GREATER OR LESS
THAN THOSE SHOWN.

The purpose of this table is to assist the investor in understanding the various
costs and expenses that an investor in the Fund will bear directly or
indirectly. For a more complete description of these costs and expenses, see
"The Fund and its Management," "Purchase of Fund Shares--Plan of Distribution"
and "Redemptions and Repurchases."

Long-term shareholders of Class B and Class C may pay more in sales charges,
including distribution fees, than the economic equivalent of the maximum
front-end sales charges permitted by the NASD.

4
<PAGE>
FINANCIAL HIGHLIGHTS
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The following ratios and per share data for a share of beneficial interest
outstanding throughout each period have been audited by PricewaterhouseCoopers
LLP, independent accountants. The financial highlights should be read in
conjunction with the financial statements, the notes thereto and the unqualified
report of independent accountants which are contained in the Statement of
Additional Information. Further information about the performance of the Fund is
contained in the Fund's Annual Report to Shareholders, which may be obtained
without charge upon request to the Fund.

Selected ratios and per share data for a share of beneficial interest
outstanding throughout each period:
<TABLE>
<CAPTION>
FOR THE YEAR ENDED DECEMBER 31,
------------------------------------------------------------------------------------------------
CLASS B SHARES 1997* 1996 1995 1994 1993 1992 1991 1990 1989
-------- -------- -------- -------- -------- -------- -------- -------- --------

<S> <C> <C> <C> <C> <C> <C> <C> <C> <C>
PER SHARE OPERATING
PERFORMANCE:
Net asset value,
beginning of period..... $ 8.92 $ 9.21 $ 8.41 $ 9.31 $ 9.30 $ 9.52 $ 9.37 $ 9.51 $ 9.42
-------- -------- -------- -------- -------- -------- -------- -------- --------
Net investment income.... 0.56 0.56 0.57 0.58 0.64 0.74 0.87 0.90 0.91
Net realized and
unrealized gain
(loss).................. 0.18 (0.29) 0.80 (0.90) 0.01 (0.22) 0.15 (0.14) 0.09
-------- -------- -------- -------- -------- -------- -------- -------- --------
Total from investment
operations.............. 0.74 0.27 1.37 (0.32) 0.65 0.52 1.02 0.76 1.00
-------- -------- -------- -------- -------- -------- -------- -------- --------
Less dividends from net
investment income....... (0.56) (0.56) (0.57) (0.58) (0.64) (0.74) (0.87) (0.90) (0.91)
-------- -------- -------- -------- -------- -------- -------- -------- --------
Net asset value, end of
period.................. $ 9.10 $ 8.92 $ 9.21 $ 8.41 $ 9.31 $ 9.30 $ 9.52 $ 9.37 $ 9.51
-------- -------- -------- -------- -------- -------- -------- -------- --------
-------- -------- -------- -------- -------- -------- -------- -------- --------

TOTAL INVESTMENT
RETURN+................. 8.56% 3.16% 16.74% (3.51)% 7.13% 5.76% 11.43% 8.49% 11.10%

RATIOS TO AVERAGE NET
ASSETS:
Expenses................. 1.26% 1.25% 1.24% 1.22% 1.18% 1.20% 1.17% 1.23% 1.19%
Net investment income.... 6.22% 6.28% 6.44% 6.57% 6.78% 7.91% 9.23% 9.60% 9.62%

SUPPLEMENTAL DATA:
Net assets, end of
period, in millions..... $5,429 $6,450 $7,955 $8,211 $12,235 $12,484 $11,736 $9,829 $10,167
Portfolio turnover
rate.................... 4% 8% 14% 26% 32% 40% 104% 54% 44%

CLASS B SHARES 1988
--------
<S> <C>
PER SHARE OPERATING
PERFORMANCE:
Net asset value,
beginning of period..... $ 9.75
--------
Net investment income.... 0.97
Net realized and
unrealized gain
(loss).................. (0.33)
--------
Total from investment
operations.............. 0.64
--------
Less dividends from net
investment income....... (0.97)
--------
Net asset value, end of
period.................. $ 9.42
--------
--------
TOTAL INVESTMENT
RETURN+................. 6.74%
RATIOS TO AVERAGE NET
ASSETS:
Expenses................. 1.21%
Net investment income.... 10.01%
SUPPLEMENTAL DATA:
Net assets, end of
period, in millions..... $10,366
Portfolio turnover
rate.................... 15%
</TABLE>

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* PRIOR TO JULY 28, 1997, THE FUND ISSUED ONE CLASS OF SHARES. ALL SHARES OF THE
FUND HELD PRIOR TO THAT DATE, OTHER THAN SHARES HELD BY CERTAIN EMPLOYEE
BENEFIT PLANS ESTABLISHED BY DEAN WITTER REYNOLDS INC. AND ITS AFFILIATE, SPS
TRANSACTION SERVICES, INC., HAVE BEEN DESIGNATED CLASS B SHARES. SHARES HELD
BY THOSE EMPLOYEE BENEFIT PLANS PRIOR TO JULY 28, 1997 HAVE BEEN DESIGNATED
CLASS D SHARES.
+ DOES NOT REFLECT THE DEDUCTION OF SALES CHARGE. CALCULATED BASED ON THE NET
ASSET VALUE AS OF THE LAST BUSINESS DAY OF THE PERIOD.

5
<PAGE>
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<TABLE>
<CAPTION>
FOR THE PERIOD
JULY 28, 1997*
THROUGH
DECEMBER 31,
CLASS A SHARES 1997
----------------
<S> <C>
PER SHARE OPERATING PERFORMANCE:
Net asset value, beginning of period.................................. $ 9.03
------
Net investment income................................................. 0.25
Net realized and unrealized gain...................................... 0.06
------
Total from investment operations...................................... 0.31
------
Less dividends from net investment income............................. (0.25)
------
Net asset value, end of period........................................ $ 9.09
------
------
TOTAL INVESTMENT RETURN+.............................................. 3.50%(1)
RATIOS TO AVERAGE NET ASSETS:
Expenses.............................................................. 0.77%(2)
Net investment income................................................. 6.57%(2)
SUPPLEMENTAL DATA:
Net assets, end of period, in thousands............................... $20,841
Portfolio turnover rate............................................... 4%

CLASS C SHARES
PER SHARE OPERATING PERFORMANCE:
Net asset value, beginning of period.................................. $ 9.03
------
Net investment income................................................. 0.23
Net realized and unrealized gain...................................... 0.14
------
Total from investment operations...................................... 0.37
------
Less dividends from net investment income............................. (0.23)
------
Net asset value, end of period........................................ $ 9.17
------
------
TOTAL INVESTMENT RETURN+.............................................. 4.14%(1)
RATIOS TO AVERAGE NET ASSETS:
Expenses.............................................................. 1.25%(2)
Net investment income................................................. 5.81%(2)
SUPPLEMENTAL DATA:
Net assets, end of period, in thousands............................... $4,385
Portfolio turnover rate............................................... 4%
</TABLE>

- -------------
* THE DATE SHARES WERE ISSUED.

+ DOES NOT REFLECT THE DEDUCTION OF SALES CHARGE. CALCULATED BASED ON THE NET
ASSET VALUE AS OF THE LAST BUSINESS DAY OF THE PERIOD.

(1) NOT ANNUALIZED.

(2) ANNUALIZED.

6
<PAGE>
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<TABLE>
<CAPTION>
FOR THE PERIOD
JULY 28, 1997*
THROUGH
DECEMBER 31,
CLASS D SHARES 1997
----------------
<S> <C>
PER SHARE OPERATING PERFORMANCE:
Net asset value, beginning of period.................................. $ 9.03
------
Net investment income................................................. 0.27
Net realized and unrealized gain...................................... 0.08
------
Total from investment operations...................................... 0.35
------
Less dividends from net investment income............................. (0.27)
------
Net asset value, end of period........................................ $ 9.11
------
------

TOTAL INVESTMENT RETURN+.............................................. 3.87%(1)

RATIOS TO AVERAGE NET ASSETS:
Expenses.............................................................. 0.52%(2)
Net investment income................................................. 6.91%(2)

SUPPLEMENTAL DATA:
Net assets, end of period, in thousands............................... $11,367
Portfolio turnover rate............................................... 4%
</TABLE>

- -------------
* THE DATE SHARES WERE FIRST ISSUED. SHAREHOLDERS WHO HELD SHARES OF THE FUND
PRIOR TO JULY 28, 1997 (THE DATE THE FUND CONVERTED TO A MULTIPLE CLASS
SHARE STRUCTURE) SHOULD REFER TO THE FINANCIAL HIGHLIGHTS OF CLASS B TO
OBTAIN THE HISTORICAL PER SHARE DATA AND RATIO INFORMATION OF THEIR SHARES.

+ CALCULATED BASED ON THE NET ASSET VALUE AS OF THE LAST BUSINESS DAY OF THE
PERIOD.

(1) NOT ANNUALIZED.

(2) ANNUALIZED.

7
<PAGE>
THE FUND AND ITS MANAGEMENT
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Morgan Stanley Dean Witter U.S. Government Securities Trust (the "Fund")
(formerly named Dean Witter U.S. Government Securities Trust) is an open-end
diversified management investment company registered under the Investment
Company Act of 1940, as amended (the "Act"). The Fund is a Trust of the type
commonly known as a "Massachusetts business trust" and was organized under the
laws of The Commonwealth of Massachusetts on September 29, 1983.

Morgan Stanley Dean Witter Advisors Inc. ("MSDW Advisors" or the "Investment
Manager"), whose address is Two World Trade Center, New York, New York 10048, is
the Fund's Investment Manager. The Investment Manager is a wholly-owned
subsidiary of Morgan Stanley Dean Witter & Co., a preeminent global financial
services firm that maintains leading market positions in each of its three
primary businesses--securities, asset management and credit services. The
Investment Manager, which was Incorporated in July, 1992 under the name Dean
Witter InterCapital Inc., changed its name to Morgan Stanley Dean Witter
Advisors Inc. on June 22, 1998.

MSDW Advisors and its wholly-owned subsidiary, Morgan Stanley Dean Witter
Services Company Inc. ("MSDW Services"), serve in various investment management,
advisory, management and administrative capacities to 102 investment companies,
twenty-eight of which are listed on the New York Stock Exchange, with combined
total assets of approximately $111.6 billion at July 31, 1998. The Investment
Manager also manages portfolios of pension plans, other institutions and
individuals which aggregated approximately $4.3 billion at such date.

The Fund has retained the Investment Manager to provide administrative
services, manage its business affairs and manage the investment of the Fund's
assets, including the placing of orders for the purchase and sale of portfolio
securities. MSDW Advisors has retained MSDW Services to perform the
aforementioned administrative services for the Fund.

The Fund's Trustees review the various services provided by or under the
direction of the Investment Manager to ensure that the Fund's general investment
policies and programs are being properly carried out and that administrative
services are being provided to the Fund in a satisfactory manner.

As full compensation for the services and facilities furnished to the Fund
and expenses of the Fund assumed by the Investment Manager, the Fund pays the
Investment Manager monthly compensation calculated daily at an annual rate of
0.50% of the daily net assets of the Fund up to $1 billion, scaled down at
various asset levels to 0.30% on assets over $12.5 billion. For the fiscal year
ended December 31, 1997, the Fund accrued total compensation to the Investment
Manager amounting to 0.43% of the Fund's average daily net assets and the Fund's
total expenses of Class B amounted to 1.26% of the Fund's average daily net
assets of Class B. Shares of Class A, Class C and Class D were first issued on
July 28, 1997. The expenses of the Fund include: the fee of the Investment
Manager; the fee pursuant to the Plan of Distribution (see "Purchase of Fund
Shares"); taxes; transfer agent, custodian and auditing fees; certain legal
fees; and printing and other expenses relating to the Fund's operations which
are not expressly assumed by the Investment Manager under its Investment
Management Agreement with the Fund.

INVESTMENT OBJECTIVE AND POLICIES
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The investment objective of the Fund is high current income consistent with
safety of principal. This investment objective may not be changed without
approval of the Fund's shareholders. The Fund seeks to achieve its objective by
investing in obligations issued or guaranteed by the U.S. Government or its
instrumentalities ("U.S. Government securities"). All such obligations are
backed by the "full faith and credit" of the United States. Investments may be
made in obligations of instrumentalities of the U.S. Government only where such
obligations are guaranteed by the U.S. Government.

U.S. Government securities include U.S. Treasury securities consisting of
Treasury bills, Treasury notes and Treasury bonds. Some of the other U.S.
Government securities in which the Fund may invest include securities of the
Federal Housing Administration, the Government National Mortgage Association,
the Department of Housing and Urban Development, the Export-Import Bank, the
Farmers Home Administration, the General Services Administration, the Maritime
Administration, Resolution Funding Corporation and the Small Business
Administration. The maturities of such securities usually range from three
months to thirty years.

The Fund is not limited as to the maturities of the U.S. Government
securities in which it may invest, except that the Fund will not purchase zero
coupon securities with remaining maturities of longer than ten years. For a
discussion of the risks of investing in U.S. Government securities (including
such securities purchased on a when-issued, delayed delivery or firm commitment
basis and zero coupon securities), see "Risk Considerations" below.

While the Fund has the ability to invest in any securities backed by the
full faith and credit of the United States, it is currently anticipated that a
substantial portion of the

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Fund's assets will be invested in Certificates of the Government National
Mortgage Association (GNMA). Should market or economic conditions warrant, this
policy is subject to change at any time at the discretion of the Investment
Manager.

DESCRIPTION OF GNMA CERTIFICATES. GNMA Certificates are mortgage-backed
securities. Each Certificate evidences an interest in a specific pool of
mortgages insured by the Federal Housing Administration or the Farmers Home
Administration (FHA) or guaranteed by the Veterans Administration (VA).
Scheduled payments of principal and interest are made to the registered holders
of GNMA Certificates. The GNMA Certificates that the Fund will invest in are of
the modified pass-through type. GNMA guarantees the timely payment of monthly
installments of principal and interest on modified pass-through certificates at
the time such payments are due, whether or not such amounts are collected by the
issuer on the underlying mortgages. The National Housing Act provides that the
full faith and credit of the United States is pledged to the timely payment of
principal and interest by GNMA of amounts due on these GNMA Certificates.

The average life of GNMA Certificates varies with the maturities of the
underlying mortgage instruments with maximum maturities of 30 years. The average
life is likely to be substantially less than the original maturity of the
mortgage pools underlying the securities as the result of prepayments or
refinancing of such mortgages or foreclosure. Such prepayments are passed
through to the registered holder with the regular monthly payments of principal
and interest, which has the effect of reducing future payments. Due to the GNMA
guarantee, foreclosures impose no risk to investment principal. The occurrence
of mortgage prepayments is affected by factors including the level of interest
rates, general economic conditions, the location and age of the mortgage and
other social and demographic conditions. As prepayment rates vary widely, it is
not possible to accurately predict the average life of a particular pool.
However, statistics indicate that the average life of the type of mortgages
backing the majority of GNMA Certificates is approximately twelve years. For
this reason, it is standard practice to treat GNMA Certificates as 30-year
mortgage-backed securities which prepay fully in the twelfth year. Pools of
mortgages with other maturities or different characteristics will have varying
assumptions for average life. The assumed average life of pools of mortgages
having terms of less than 30 years is less than twelve years, but typically not
less than five years.

The coupon rate of interest of GNMA Certificates is lower than the interest
rate paid on the VA-guaranteed or FHA-insured mortgages underlying the
Certificates, but only by the amount of the fees paid to GNMA and the issuer.

Yields on pass-through securities are typically quoted by investment dealers
and vendors based on the maturity of the underlying instruments and the
associated average life assumption. In periods of falling interest rates the
rate of prepayment tends to increase, thereby shortening the actual average life
of a pool of mortgage-related securities. Conversely, in periods of rising rates
the rate of prepayment tends to decrease, thereby lengthening the actual average
life of the pool. Reinvestment by the Fund of prepayments may occur at higher or
lower interest rates than the original investment. Historically, actual average
life has been consistent with the twelve-year assumption referred to above. The
actual yield of each GNMA Certificate is influenced by the prepayment experience
of the mortgage pool underlying the Certificates. Interest on GNMA Certificates
is paid monthly rather than semi-annually as for traditional bonds.

The Fund will invest in mortgage pass-through securities representing
participation interests in pools of residential mortgage loans originated by
United States governmental or private lenders such as banks, broker-dealers and
financing corporations and guaranteed, to the extent provided in such
securities, by the United States Government or one of its agencies or
instrumentalities. Such securities, which are ownership interests in the
underlying mortgage loans, differ from conventional debt securities, which
provide for periodic payment of interest in fixed amounts (usually
semi-annually) and principal payments at maturity or on specified call dates.
Mortgage pass-through securities provide for monthly payments that are a
"pass-through" of the monthly interest and principal payments (including any
prepayments) made by the individual borrowers on the pooled mortgage loans, net
of any fees paid to the guarantor of such securities and the servicer of the
underlying mortgage loans. The guaranteed mortgage pass-through securities in
which the Fund may invest include those issued or guaranteed by GNMA or other
entities which securities are backed by the full faith and credit of the United
States.

Certificates for mortgage-backed securities evidence an interest in a
specific pool of mortgages. These certificates are, in most cases, "modified
pass-through" instruments, wherein the issuing agency guarantees the payment of
principal and interest on mortgages underlying the certificates, whether or not
such amounts are collected by the issuer on the underlying mortgages.

ADJUSTABLE RATE MORTGAGE SECURITIES. The Fund may also invest in adjustable
rate mortgage securities ("ARMs"), which are pass-through mortgage securities
collateralized by mortgages with adjustable rather than fixed rates. ARMs
eligible for inclusion in a mortgage pool generally provide for a fixed initial
mortgage interest rate for either the first three, six, twelve or thirteen
scheduled monthly payments. Thereafter, the interest rates are subject to
periodic adjustment based on changes to a designated benchmark index.

ARMs contain maximum and minimum rates beyond which the mortgage interest
rate may not vary over the lifetime of the security. In addition, certain ARMs
provide for additional limitations on the maximum amount by which

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<PAGE>
the mortgage interest rate may adjust for any single adjustment period.
Alternatively, certain ARMs contain limitations on changes in the required
monthly payment. In the event that a monthly payment is not sufficient to pay
the interest accruing on an ARM, any such excess interest is added to the
principal balance of the mortgage loan, which is repaid through future monthly
payments. If the monthly payment for such an instrument exceeds the sum of the
interest accrued at the applicable mortgage interest rate and the principal
payment required at such point to amortize the outstanding principal balance
over the remaining term of the loan, the excess is utilized to reduce the then
outstanding principal balance of the ARM.

COLLATERALIZED MORTGAGE OBLIGATIONS AND MULTICLASS PASS-THROUGH
SECURITIES. Collateralized mortgage obligations or "CMOs" are debt obligations
collateralized by mortgage loans or mortgage pass-through securities. Typically,
CMOs are collateralized by GNMA, FNMA or FHLMC Certificates, but also may be
collateralized by whole loans or private mortgage pass-through securities (such
collateral collectively hereinafter referred to as "Mortgage Assets").
Multiclass pass-through securities are equity interests in a trust composed of
Mortgage Assets. Payments of principal of and interest on the Mortgage Assets,
and any reinvestment income thereon, provide the funds to pay debt service on
the CMOs or make scheduled distributions on the multiclass pass-through
securities. CMOs may be issued by agencies or instrumentalities of the United
States government, or by private originators of, or investors in, mortgage
loans, including savings and loan associations, mortgage banks, commercial
banks, investment banks and special purpose subsidiaries of the foregoing.
However, the Fund will only invest in CMOs which are backed by the full faith
and credit of the United States.

The issuer of a series of CMOs may elect to be treated as a Real Estate
Mortgage Investment Conduit ("REMIC"). REMICs include governmental and/or
private entities that issue a fixed pool of mortgages secured by an interest in
real property. REMICs are similar to CMOs in that they issue multiple classes of
securities, but unlike CMOs, which are required to be structured as debt
securities, REMICs may be structured as indirect ownership interests in the
underlying assets of the REMICs themselves. However, there are no effects on the
Fund from investing in CMOs issued by entities that have elected to be treated
as REMICs, and all future references to CMOs shall also be deemed to include
REMICs. The Fund may invest without limitation in CMOs.

In a CMO, a series of bonds or certificates is issued in multiple classes.
Each class of CMOs, often referred to as a "tranche," is issued at a specific
fixed or floating coupon rate and has a stated maturity or final distribution
date. Principal prepayments on the Mortgage Assets may cause the CMOs to be
retired substantially earlier than their stated maturities or final distribution
dates. Interest is paid or accrues on all classes of the CMOs on a monthly,
quarterly or semi-annual basis. Certain CMOs may have variable or floating
interest rates and others may be stripped (securities which provide only the
principal or interest feature of the underlying security).

The principal of and interest on the Mortgage Assets may be allocated among
the several classes of a CMO series in a number of different ways. Generally,
the purpose of the allocation of the cash flow of a CMO to the various classes
is to obtain a more predictable cash flow to the individual tranches than exists
with the underlying collateral of the CMO. As a general rule, the more
predictable the cash flow is on a CMO tranche, the lower the anticipated yield
will be on that tranche at the time of issuance relative to prevailing market
yields on mortgage-backed securities. As part of the process of creating more
predictable cash flows on most of the tranches in a series of CMOs, one or more
tranches generally must be created that absorb most of the volatility in the
cash flows on the underlying mortgage loans. The yields on these tranches are
generally higher than prevailing market yields on mortgage-backed securities
with similar maturities. As a result of the uncertainty of the cash flows of
these tranches, the market prices of and yield on these tranches generally are
more volatile.

The Fund also may invest in, among other things, parallel pay CMOs and
Planned Amortization Class CMOs ("PAC Bonds"). Parallel pay CMOs are structured
to provide payments of principal on each payment date to more than one class.
These simultaneous payments are taken into account in calculating the stated
maturity date or final distribution date of each class, which, as with other CMO
structures, must be retired by its stated maturity date or final distribution
date but may be retired earlier. PAC Bonds generally require payments of a
specified amount of principal on each payment date. PAC Bonds always are
parallel pay CMOs with the required principal payment on such securities having
the highest priority after interest has been paid to all classes.

For a discussion of the risks of investing in mortgage-backed securities,
see "Risk Considerations" below.

The purchase or retention of stripped mortgage-backed securities, CMOs and
REMICs investments will be made only in conformity with the provisions of
Section 703.5 of the National Credit Union Administration Rules and Regulations,
as such provisions became effective on December 2, 1991.

RISK CONSIDERATIONS

The net asset value of the Fund's shares will fluctuate with changes in the
market value of its portfolio securities. Neither the value nor the yield of the
U.S. Government securities invested in by the Fund (or the value or yield of the
shares of the Fund) is guaranteed by the U.S. Government. Such values and yield
will fluctuate with changes in prevailing interest rates and other factors.

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<PAGE>
Generally, as prevailing interest rates rise, the value of the U.S.
Government securities held by the Fund, and, concomitantly, the net asset value
of the Fund's shares, will fall. Such securities with longer maturities
generally tend to produce higher yields and are subject to greater market
fluctuation as a result of changes in interest rates than debt securities with
shorter maturities. As noted above, except with regard to zero coupon
securities, the Fund is not limited as to the maturities of the U.S. Government
securities in which it may invest.

RISKS OF MORTGAGE-BACKED SECURITIES. Mortgage-backed securities have certain
different characteristics than traditional debt securities. Among the major
differences are that interest and principal payments are made more frequently,
usually monthly, and that principal may be prepaid at any time because the
underlying mortgage loans or other assets generally may be prepaid at any time.
As a result, if the Fund purchases such a security at a premium, a prepayment
rate that is faster than expected may reduce yield to maturity, while a
pre-payment rate that is slower than expected may have the opposite effect of
increasing yield to maturity. Alternatively, if the Fund purchases these
securities at a discount, faster than expected prepayments will increase, while
slower than expected prepayments may reduce, yield to maturity.

Mortgage-backed securities, like all fixed-income securities, generally
decrease in value as a result of increases in interest rates. In addition,
although generally the value of fixed-income securities increases during periods
of falling interest rates, mortgage-backed securities may benefit less than
other fixed-income securities from declining interest rates because of the risk
of prepayments. As discussed above under "Description of GNMA Certificates," the
assumed average life of mortgages backing the majority of GNMA Certificates is
twelve years. This average life is likely to be substantially shorter than the
original maturity of the mortgage pools underlying the certificates, as a pool's
duration may be shortened by unscheduled or early payments of principal on the
underlying mortgages. As prepayment rates vary widely, it is not possible to
accurately predict the average life of a particular pool.

Although the extent of prepayments on a pool of mortgage loans depends on
various factors, including the prevailing level of interest rates, general
economic conditions, the location and age of the mortgage and other social and
demographic conditions, as a general rule prepayments on fixed rate mortgage
loans will increase during a period of falling interest rates and decrease
during a period of rising interest rates. If the Fund has purchased securities
backed by pools containing mortgages whose yields exceed the prevailing interest
rate, any premium paid for such securities may be lost. As a result, the net
asset value of shares of the Fund and the Fund's ability to achieve its
investment objective may be adversely affected by mortgage prepayments. Amounts
available for reinvestment by the Fund are likely to be greater during a period
of declining interest rates and, as a result, likely to be reinvested at lower
interest rates than during a period of rising interest rates.

There are certain risks associated specifically with CMOs. A number of
different factors, including the extent of prepayment of principal of the
Mortgage Assets, affect the availability of cash for principal payments by the
CMO issuer on any payment date and, accordingly, affect the timing of principal
payments on each CMO class.

WHEN-ISSUED AND DELAYED DELIVERY SECURITIES AND FORWARD COMMITMENTS. From time
to time, in the ordinary course of business, the Fund may purchase securities on
a when-issued or delayed delivery basis or may purchase or sell securities on a
forward commitment basis. When such transactions are negotiated, the price is
fixed at the time of the commitment, but delivery and payment can take place
between one month and 120 days after the date of the commitment. While the Fund
will only purchase securities on a when-issued, delayed delivery or forward
commitment basis with the intention of acquiring the securities, the Fund may
sell the securities before the settlement date, if it is deemed advisable. The
securities so purchased or sold are subject to market fluctuation and no
interest accrues to the purchaser during this period. At the time the Fund makes
the commitment to purchase or sell securities on a when-issued, delayed delivery
or forward commitment basis, it will record the transaction and thereafter
reflect the value, each day, of such security purchased or, if a sale, the
proceeds to be received, in determining its net asset value. At the time of
delivery of the securities, their value may be more or less than the purchase or
sale price. The Fund will also establish a segregated account with its custodian
bank in which it will continually maintain cash or cash equivalents or other
liquid portfolio securities equal in value to commitments to purchase securities
on a when-issued, delayed delivery or forward commitment basis. There is no
overall limit on the percentage of the Fund's assets which may be committed to
the purchase of securities on a when-issued, delayed delivery or forward
commitment basis. An increase in the percentage of the Fund's assets committed
to the purchase of securities on a when-issued, delayed delivery or forward
commitment basis may increase the volatility of the Fund's net asset value.

ZERO COUPON SECURITIES. A portion of the U.S. Government securities purchased
by the Fund may be zero coupon securities with maturity dates in each case no
later than ten years from the settlement date for the purchase of such security.
Such securities are purchased at a discount from their face amount, giving the
purchaser the right to receive their full value at maturity. The interest earned
on such securities is, implicitly, automatically compounded and paid out at
maturity. While such compounding at a constant rate eliminates the risk of
receiving lower yields upon reinvestment of interest if prevailing interest
rates decline, the owner of a zero coupon security will be unable to participate
in higher yields upon reinvestment of interest received on interest-paying
securities if prevailing interest rates rise.

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A zero coupon security pays no interest to its holder during its life.
Therefore, to the extent the Fund invests in zero coupon securities, it will not
receive current cash available for distribution to shareholders. In addition,
zero coupon securities are subject to substantially greater price fluctuations
during periods of changing prevailing interest rates than are comparable
securities which pay interest on a current basis. Current federal tax law
requires that a holder (such as the Fund) of a zero coupon security accrue a
portion of the discount at which the security was purchased as income each year
even though the Fund receives no interest payments in cash on the security
during the year.

YEAR 2000. The investment management services provided to the Fund by the
Investment Manager and the services provided to shareholders by the Distributor
and the Transfer Agent depend on the smooth functioning of their computer
systems. Many computer software systems in use today cannot recognize the year
2000, but revert to 1900 or some other date, due to the manner in which dates
were encoded and calculated. That failure could have a negative impact on the
handling of securities trades, pricing and account services. The Investment
Manager, the Distributor and the Transfer Agent have been actively working on
necessary changes to their own computer systems to prepare for the year 2000 and
expect that their systems will be adapted before that date, but there can be no
assurance that they will be successful, or that interaction with other
non-complying computer systems will not impair their services at that time.

In addition, it is possible that the markets for securities in which the
Fund invests may be detrimentally affected by computer failures throughout the
financial services industry beginning January 1, 2000. Improperly functioning
trading systems may result in settlement problems and liquidity issues. In
addition, corporate and governmental data processing errors may result in
production problems for individual companies and overall economic uncertainties.
Earnings of individual issuers will be affected by remediation costs, which may
be substantial and may be reported inconsistently in U.S. and foreign financial
statements. Accordingly, the Fund's investments may be adversely affected.

For additional risk disclosure, please refer to the discussion of specific
investments above in "Investment Objective and Policies."

------------

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 objectives and policies as the Fund.

PORTFOLIO TRADING

The Fund is managed within MSDW Advisors' Taxable Fixed-Income Group, which
manages 23 funds and fund portfolios, with approximately $13.9 billion in assets
at July 31, 1998. Rajesh K. Gupta, Senior Vice President of MSDW Advisors and a
member of MSDW Advisors' Taxable Fixed-Income Group, has been the primary
portfolio manager of the Fund and has been managing portfolios comprised of
government securities at MSDW Advisors for over five years.

Although the Fund does not intend to engage in short-term trading of
portfolio securities as a means of achieving its investment objective, it may
sell portfolio securities without regard to the length of time they have been
held whenever such sale will in the Investment Manager's opinion strengthen the
Fund's position and contribute to its investment objective. The portfolio
trading engaged in by the Fund may result in its portfolio turnover rate
exceeding 100%. Brokerage commissions are not normally charged on the purchase
or sale of U.S. Government obligations, but such transactions may involve costs
in the form of spreads between bid and asked prices. Pursuant to an order of the
Securities and Exchange Commission, the Fund may effect principal transactions
in certain money market instruments with Dean Witter Reynolds Inc., a
broker-dealer affiliate of MSDW Advisors. In addition, the Fund may incur
brokerage commissions on transactions conducted through Dean Witter Reynolds
Inc., Morgan Stanley & Co. Incorporated and other brokers and dealers that are
affiliates of MSDW Advisors.

PURCHASE OF FUND SHARES
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GENERAL

The Fund offers each Class of its shares for sale to the public on a continuous
basis. Pursuant to a Distribution Agreement between the Fund and Morgan Stanley
Dean Witter Distributors Inc. ("MSDW Distributors" or the "Distributor"), an
affiliate of the Investment Manager, shares of the Fund are distributed by the
Distributor and offered by Dean Witter Reynolds Inc. ("DWR"), a selected dealer
and subsidiary of Morgan Stanley Dean Witter & Co. and other dealers which have
entered into selected dealer agreements with the Distributor ("Selected Broker-
Dealers"). It is anticipated that DWR will undergo a change of corporate name
which is expected to incorporate the brand name of "Morgan Stanley Dean Witter,"
pending approval of various regulatory authorities. The principal executive
office of the Distributor is located at Two World Trade Center, New York, New
York 10048.

The Fund offers four classes of shares (each, a "Class"). Class A shares are
sold to investors with an initial sales charge that declines to zero for larger
purchases;

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<PAGE>
however, Class A shares sold without an initial sales charge are subject to a
contingent deferred sales charge ("CDSC") of 1.0% if redeemed within one year of
purchase, except for certain specific circumstances. Class B shares are sold
without an initial sales charge but are subject to a CDSC (scaled down from 5.0%
to 1.0%) payable upon most redemptions within six years after purchase. (Class B
shares purchased by certain qualified plans are subject to a CDSC scaled down
from 2.0% to 1.0% if redeemed within three years after purchase.) Class C shares
are sold without an initial sales charge but are subject to a CDSC of 1.0% on
most redemptions made within one year after purchase. Class D shares are sold
without an initial sales charge or CDSC and are available only to investors
meeting an initial investment minimum of $5 million ($25 million for certain
qualified plans), and to certain other limited categories of investors. At the
discretion of the Board of Trustees of the Fund, Class A shares may be sold to
categories of investors in addition to those set forth in this prospectus at net
asset value without a front-end sales charge, and Class D shares may be sold to
certain other categories of investors, in each case as may be described in the
then current prospectus of the Fund. See "Alternative Purchase Arrangements--
Selecting a Particular Class" for a discussion of factors to consider in
selecting which Class of shares to purchase.

The minimum initial purchase is $1,000 for each Class of shares, although
Class D shares are only available to persons investing $5 million ($25 million
for certain qualified plans) or more and to certain other limited categories of
investors. For the purpose of meeting the minimum $5 million (or $25 million)
initial investment for Class D shares, and subject to the $1,000 minimum initial
investment for each Class of the Fund, an investor's existing holdings of Class
A shares of the Fund and other Morgan Stanley Dean Witter Funds that are
multiple class funds ("Morgan Stanley Dean Witter Multi-Class Funds") and shares
of Morgan Stanley Dean Witter Funds sold with a front-end sales charge ("FSC
Funds") and concurrent investments in Class D shares of the Fund and other
Morgan Stanley Dean Witter Multi-Class Funds will be aggregated. Subsequent
purchases of $100 or more may be made by sending a check, payable to Morgan
Stanley Dean Witter U.S. Government Securities Trust, directly to Morgan Stanley
Dean Witter Trust FSB (the "Transfer Agent" or "MSDW Trust") at P.O. Box 1040,
Jersey City, NJ 07303 or by contacting a Morgan Stanley Dean Witter Financial
Advisor or other Selected broker-dealer representative. When purchasing shares
of the Fund, investors must specify whether the purchase is for Class A, Class
B, Class C or Class D shares. If no Class is specified, the Transfer Agent will
not process the transaction until the proper Class is identified. The minimum
initial purchase, in the case of investments through EasyInvest-SM-, an
automatic purchase plan (see "Shareholder Services"), is $100, provided that the
schedule of automatic investments will result in investments totalling at least
$1,000 within the first twelve months. The minimum initial purchase in the case
of an "Education IRA" is $500, if the Distributor has reason to believe that
additional investments will increase the investment in the account to $1,000
within three years. In the case of investments pursuant to (i) Systematic
Payroll Deduction Plans (including Individual Retirement Plans), (ii) the MSDW
Advisors mutual fund asset allocation program and (iii) fee-based programs
approved by the Distributor, pursuant to which participants pay an asset based
fee for services in the nature of investment advisory, administrative and/or
brokerage services, the Fund, in its discretion, may accept investments without
regard to any minimum amounts which would otherwise be required, provided, in
the case of Systematic Payroll Deduction Plans, that the Distributor has reason
to believe that additional investments will increase the investment in all
accounts under such Plans to at least $1,000. Certificates for shares purchased
will not be issued unless requested by the shareholder in writing to the
Transfer Agent.

Shares of the Fund are sold through the Distributor on a normal three
business day settlement basis; that is, payment generally is due on or before
the third business day (settlement date) after the order is placed with the
Distributor. Shares of the Fund purchased through the Distributor are entitled
to dividends beginning on the next business day following settlement date. Since
DWR and other Selected Broker-Dealers forward investors' funds on settlement
date, they will benefit from the temporary use of the funds where payment is
made prior thereto. Shares purchased through the Transfer Agent are entitled to
dividends beginning on the next business day following receipt of an order. As
noted above, orders placed directly with the Transfer Agent must be accompanied
by payment. Investors will be entitled to receive capital gains distributions if
their order is received by the close of business on the day prior to the record
date for such distributions. Sales personnel of a Selected Broker-Dealer are
compensated for selling shares of the Fund by the Distributor or any of its
affiliates and/or the Selected Broker-Dealer. In addition, some sales personnel
of the Selected Broker-Dealer will receive various types of non-cash
compensation as special sales incentives, including trips, educational and/or
business seminars and merchandise. The Fund and the Distributor reserve the
right to reject any purchase order.

ALTERNATIVE PURCHASE ARRANGEMENTS

The Fund offers several Classes of shares to investors designed to provide them
with the flexibility of selecting an investment best suited to their needs. The
general public is offered three Classes of shares: Class A shares, Class B
shares and Class C shares, which differ principally in terms of sales charges
and rate of expenses to which they are subject. A fourth Class of shares, Class
D shares, is offered only to limited categories of investors (see "No Load
Alternative--Class D Shares" below).

Each Class A, Class B, Class C or Class D share of the Fund represents an
identical interest in the investment

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<PAGE>
portfolio of the Fund except that Class A, Class B and Class C shares bear the
expenses of the ongoing shareholder service fees, Class B and Class C shares
bear the expenses of the ongoing distribution fees and Class A, Class B and
Class C shares which are redeemed subject to a CDSC bear the expense of the
additional incremental distribution costs resulting from the CDSC applicable to
shares of those Classes. The ongoing distribution fees that are imposed on Class
A, Class B and Class C shares will be imposed directly against those Classes and
not against all assets of the Fund and, accordingly, such charges against one
Class will not affect the net asset value of any other Class or have any impact
on investors choosing another sales charge option. See "Plan of Distribution"
and "Redemptions and Repurchases."

Set forth below is a summary of the differences between the Classes and the
factors an investor should consider when selecting a particular Class. This
summary is qualified in its entirety by detailed discussion of each Class that
follows this summary.

CLASS A SHARES. Class A shares are sold at net asset value plus an initial
sales charge of up to 4.25%. The initial sales charge is reduced for certain
purchases. Investments of $1 million or more (and investments by certain other
limited categories of investors) are not subject to any sales charges at the
time of purchase but are subject to a CDSC of 1.0% on redemptions made within
one year after purchase, except for certain specific circumstances. Class A
shares are also subject to a 12b-1 fee of up to 0.25% of the average daily net
assets of the Class. See "Initial Sales Charge Alternative--Class A Shares."

CLASS B SHARES. Class B shares are offered at net asset value with no initial
sales charge but are subject to a CDSC (scaled down from 5.0% to 1.0%) if
redeemed within six years of purchase. (Class B shares purchased by certain
qualified plans are subject to a CDSC scaled down from 2.0% to 1.0% if redeemed
within three years after purchase.) This CDSC may be waived for certain
redemptions. Class B shares are also subject to an annual 12b-1 fee of 0.75%
(0.65% on amounts over $10 billion) of the lesser of: (a) the average daily
aggregate gross sales of the Fund's Class B shares since the inception of the
Fund (not including reinvestments of dividends or capital gains distributions),
less the average daily aggregate net asset value of the Fund's Class B shares
redeemed since the Fund's inception upon which a CDSC has been imposed or
waived, or (b) the average daily net assets of Class B. The Class B shares'
distribution fee will cause that Class to have higher expenses and pay lower
dividends than Class A or Class D shares.

After approximately ten (10) years, Class B shares will convert
automatically to Class A shares of the Fund, based on the relative net asset
values of the shares of the two Classes on the conversion date. In addition, a
certain portion of Class B shares that have been acquired through the
reinvestment of dividends and distributions will be converted at that time. See
"Contingent Deferred Sales Charge Alternative--Class B Shares."

CLASS C SHARES. Class C shares are sold at net asset value with no initial
sales charge but are subject to a CDSC of 1.0% on redemptions made within one
year after purchase. This CDSC may be waived for certain redemptions. They are
subject to an annual 12b-1 fee of up to 0.75% of the average daily net assets of
the Class C shares. The Class C shares' distribution fee may cause that Class to
have higher expenses and pay lower dividends than Class A or Class D shares. See
"Level Load Alternative--Class C Shares."

CLASS D SHARES. Class D shares are available only to limited categories of
investors (see "No Load Alternative-- Class D Shares" below). Class D shares are
sold at net asset value with no initial sales charge or CDSC. They are not
subject to any 12b-1 fees. See "No Load Alternative-- Class D Shares."

SELECTING A PARTICULAR CLASS. In deciding which Class of Fund shares to
purchase, investors should consider the following factors, as well as any other
relevant facts and circumstances:

The decision as to which Class of shares is more beneficial to an investor
depends on the amount and intended length of his or her investment. Investors
who prefer an initial sales charge alternative may elect to purchase Class A
shares. Investors qualifying for significantly reduced or, in the case of
purchases of $1 million or more, no initial sales charges may find Class A
shares particularly attractive because similar sales charge reductions are not
available with respect to Class B or Class C shares. Moreover, Class A shares
are subject to lower ongoing expenses than are Class B or Class C shares over
the term of the investment. As an alternative, Class B and Class C shares are
sold without any initial sales charge so the entire purchase price is
immediately invested in the Fund. Any investment return on these additional
investment amounts may partially or wholly offset the higher annual expenses of
these Classes. Because the Fund's future return cannot be predicted, however,
there can be no assurance that this would be the case.

Finally, investors should consider the effect of the CDSC period and any
conversion rights of the Classes in the context of their own investment time
frame. For example, although Class C shares are subject to a significantly lower
CDSC upon redemptions, they do not, unlike Class B shares, convert into Class A
shares after approximately ten years, and, therefore, are subject to an ongoing
12b-1 fee of 0.75% (rather than the 0.25% fee applicable to Class A shares) for
an indefinite period of time. Thus, Class B shares may be more attractive than
Class C shares to investors with longer term investment outlooks. Other
investors, however, may elect to purchase Class C shares if, for example, they
determine that they do not wish to be subject

14
<PAGE>
to a front-end sales charge and they are uncertain as to the length of time they
intend to hold their shares.

For the purpose of meeting the $5 million (or $25 million) minimum
investment amount for Class D shares, holdings of Class A shares in all Morgan
Stanley Dean Witter Multi-Class Funds, shares of FSC Funds and shares of Morgan
Stanley Dean Witter Funds for which such shares have been exchanged will be
included together with the current investment amount.

Sales personnel may receive different compensation for selling each Class of
shares. Investors should understand that the purpose of a CDSC is the same as
that of the initial sales charge in that the sales charges applicable to each
Class provide for the financing of the distribution of shares of that Class.

Set forth below is a chart comparing the sales charge, 12b-1 fees and
conversion options applicable to each Class of shares:

<TABLE>
<CAPTION>
CONVERSION
CLASS SALES CHARGE 12b-1 FEE FEATURE
<C> <S> <C> <C>
A Maximum 4.25% initial 0.25% No
sales charge reduced for
purchases of $25,000 and
over; shares sold without
an initial sales charge
generally subject to a
1.0% CDSC during first
year.
B Maximum 5.0% CDSC during 0.75% B shares
the first year decreasing (0.65% on convert to A
to 0 after six years amounts shares
over $10 automatically
billion) after
approximately
ten years
C 1.0% CDSC during first 0.75% No
year
D None None No
</TABLE>

See "Purchase of Fund Shares" and "The Fund and its Management" for a
complete description of the sales charges and service and distribution fees for
each Class of shares and "Determination of Net Asset Value," "Dividends,
Distributions and Taxes" and "Shareholder Services--Exchange Privilege" for
other differences between the Classes of shares.

INITIAL SALES CHARGE ALTERNATIVE-- CLASS A SHARES

Class A shares are sold at net asset value plus an initial sales charge. In some
cases, reduced sales charges may be available, as described below. Investments
of $1 million or more (and investments by certain other limited categories of
investors) are not subject to any sales charges at the time of purchase but are
subject to a CDSC of 1.0% on redemptions made within one year after purchase
(calculated from the last day of the month in which the shares were purchased),
except for certain specific circumstances. The CDSC will be assessed on an
amount equal to the lesser of the current market value or the cost of the shares
being redeemed. The CDSC will not be imposed (i) in the circumstances set forth
below in the section "Contingent Deferred Sales Charge Alternative--Class B
Shares-- CDSC Waivers," except that the references to six years in the first
paragraph of that section shall mean one year in the case of Class A shares, and
(ii) in the circumstances identified in the section "Additional Net Asset Value
Purchase Options" below. Class A shares are also subject to an annual 12b-1 fee
of up to 0.25% of the average daily net assets of the Class.

The offering price of Class A shares will be the net asset value per share
next determined following receipt of an order (see "Determination of Net Asset
Value" below), plus a sales charge (expressed as a percentage of the offering
price) on a single transaction as shown in the following table:

<TABLE>
<CAPTION>
SALES CHARGE
-------------------------------------
PERCENTAGE OF APPROXIMATE
AMOUNT OF PUBLIC OFFERING PERCENTAGE OF
SINGLE TRANSACTION PRICE AMOUNT INVESTED
- --------------------------- ----------------- ------------------
<S> <C> <C>
Less than $25,000.......... 4.25% 4.44%
$25,000 but less
than $50,000............. 4.00% 4.17%
$50,000 but less
than $100,000............ 3.50% 3.63%
$100,000 but less
than $250,000............ 2.75% 2.83%
$250,000 but less
than $1 million.......... 1.75% 1.78%
$1 million and over........ 0 0
</TABLE>

Upon notice to all Selected Broker-Dealers, the Distributor may reallow up
to the full applicable sales charge as shown in the above schedule during
periods specified in such notice. During periods when 90% or more of the sales
charge is reallowed, such Selected Broker-Dealers may be deemed to be
underwriters as that term is defined in the Securities Act of 1933.

The above schedule of sales charges is applicable to purchases in a single
transaction by, among others: (a) an individual; (b) an individual, his or her
spouse and their children under the age of 21 purchasing shares for his, her or
their own accounts; (c) a trustee or other fiduciary purchasing shares for a
single trust estate or a single fiduciary account; (d) a pension, profit-sharing
or other employee benefit plan qualified or non-qualified under Section 401 of
the Internal Revenue Code; (e) tax-exempt organizations enumerated in Section
501(c)(3) or (13) of the Internal Revenue Code; (f) employee benefit plans
qualified under Section 401 of the Internal Revenue Code of a single employer or
of employers who are "affiliated persons" of each other within the meaning of
Section 2(a)(3)(c) of the Act; and for investments in Individual Retirement
Accounts of employees of a single employer through Systematic Payroll Deduction
plans; or (g) any other organized group of persons, whether incorporated or not,
provided the organization has been in existence for at least six months and has

15
<PAGE>
some purpose other than the purchase of redeemable securities of a registered
investment company at a discount.

COMBINED PURCHASE PRIVILEGE. Investors may have the benefit of reduced sales
charges in accordance with the above schedule by combining purchases of Class A
shares of the Fund in single transactions with the purchase of Class A shares of
other Morgan Stanley Dean Witter Multi-Class Funds and shares of FSC Funds. The
sales charge payable on the purchase of the Class A shares of the Fund, the
Class A shares of the other Morgan Stanley Dean Witter Multi-Class Funds and the
shares of the FSC Funds will be at their respective rates applicable to the
total amount of the combined concurrent purchases of such shares.

RIGHT OF ACCUMULATION. The above persons and entities may benefit from a
reduction of the sales charges in accordance with the above schedule if the
cumulative net asset value of Class A shares purchased in a single transaction,
together with shares of the Fund and other Morgan Stanley Dean Witter Funds
previously purchased at a price including a front-end sales charge (including
shares of the Fund and other Morgan Stanley Dean Witter Funds acquired in
exchange for those shares, and including in each case shares acquired through
reinvestment of dividends and distributions), which are held at the time of such
transaction, amounts to $25,000 or more. If such investor has a cumulative net
asset value of shares of FSC Funds and Class A and Class D shares that, together
with the current investment amount, is equal to at least $5 million ($25 million
for certain qualified plans), such investor is eligible to purchase Class D
shares subject to the $1,000 minimum initial investment requirement of that
Class of the Fund. See "No Load Alternative--Class D Shares" below.

The Distributor must be notified by DWR or a Selected Broker-Dealer or the
shareholder at the time a purchase order is placed that the purchase qualifies
for the reduced charge under the Right of Accumulation. Similar notification
must be made in writing by the dealer or shareholder when such an order is
placed by mail. The reduced sales charge will not be granted if: (a) such
notification is not furnished at the time of the order; or (b) a review of the
records of the Selected Broker-Dealer or the Transfer Agent fails to confirm the
investor's represented holdings.

LETTER OF INTENT. The foregoing schedule of reduced sales charges will also be
available to investors who enter into a written Letter of Intent providing for
the purchase, within a thirteen-month period, of Class A shares of the Fund from
DWR or other Selected Broker-Dealers. The cost of Class A shares of the Fund or
shares of other Morgan Stanley Dean Witter Funds which were previously purchased
at a price including a front-end sales charge during the 90-day period prior to
the date of receipt by the Distributor of the Letter of Intent, or of Class A
shares of the Fund or shares of other Morgan Stanley Dean Witter Funds acquired
in exchange for shares of such funds purchased during such period at a price
including a front-end sales charge, which are still owned by the shareholder,
may also be included in determining the applicable reduction.

ADDITIONAL NET ASSET VALUE PURCHASE OPTIONS. In addition to investments of $1
million or more, Class A shares also may be purchased at net asset value by the
following:

(1) trusts for which MSDW Trust (an affiliate of the Investment Manager)
provides discretionary trustee services;

(2) persons participating in a fee-based program approved by the
Distributor, pursuant to which such persons pay an asset based fee for services
in the nature of investment advisory, administrative and/or brokerage services
(such investments are subject to all of the terms and conditions of such
programs, which may include termination fees, mandatory redemption upon
termination and such other circumstances as specified in the programs'
agreements, and restrictions on transferability of Fund shares);

(3) employer-sponsored 401(k) and other plans qualified under Section 401(a)
of the Internal Revenue Code ("Qualified Retirement Plans") with at least 200
eligible employees and for which MSDW Trust serves as Trustee or DWR's
Retirement Plan Services serves as recordkeeper pursuant to a written
Recordkeeping Services Agreement;

(4) Qualified Retirement Plans for which MSDW Trust serves as Trustee or
DWR's Retirement Plan Services serves as recordkeeper pursuant to a written
Recordkeeping Services Agreement whose Class B shares have converted to Class A
shares, regardless of the plan's asset size or number of eligible employees;

(5) investors who are clients of a Morgan Stanley Dean Witter Financial
Advisor who joined Morgan Stanley Dean Witter from another investment firm
within six months prior to the date of purchase of Fund shares by such
investors, if the shares are being purchased with the proceeds from a redemption
of shares of an open-end proprietary mutual fund of the Financial Advisor's
previous firm which imposed either a front-end or deferred sales charge,
provided such purchase was made within sixty days after the redemption and the
proceeds of the redemption had been maintained in the interim in cash or a money
market fund; and

(6) other categories of investors, at the discretion of the Board, as
disclosed in the then current prospectus of the Fund.

No CDSC will be imposed on redemptions of shares purchased pursuant to
paragraphs (1), (2) or (5), above.

For further information concerning purchases of the Fund's shares, contact
DWR or another Selected Broker-Dealer or consult the Statement of Additional
Information.

16
<PAGE>
CONTINGENT DEFERRED SALES CHARGE ALTERNATIVE--CLASS B SHARES

Class B shares are sold at net asset value next determined without an initial
sales charge so that the full amount of an investor's purchase payment may be
immediately invested in the Fund. A CDSC, however, will be imposed on most Class
B shares redeemed within six years after purchase. The CDSC will be imposed on
any redemption of shares if after such redemption the aggregate current value of
a Class B account with the Fund falls below the aggregate amount of the
investor's purchase payments for Class B shares made during the six years (or,
in the case of shares held by certain Qualified Retirement Plans, three years)
preceding the redemption. In addition, Class B shares are subject to an annual
12b-1 fee of 0.75% (0.65% on amounts over $10 billion) of the lesser of: (a) the
average daily aggregate gross sales of the Fund's Class B shares since the
inception of the Fund (not including reinvestments of dividends or capital gains
distributions), less the average daily aggregate net asset value of the Fund's
Class B shares redeemed since the Fund's inception upon which a CDSC has been
imposed or waived, or (b) the average daily net assets of Class B.

Except as noted below, Class B shares of the Fund which are held for six
years or more after purchase (calculated from the last day of the month in which
the shares were purchased) will not be subject to any CDSC upon redemption.
Shares redeemed earlier than six years after purchase may, however, be subject
to a CDSC which will be a percentage of the dollar amount of shares redeemed and
will be assessed on an amount equal to the lesser of the current market value or
the cost of the shares being redeemed. The size of this percentage will depend
upon how long the shares have been held, as set forth in the following table:

<TABLE>
<CAPTION>
YEAR SINCE PURCHASE CDSC AS A PERCENTAGE
PAYMENT MADE OF AMOUNT REDEEMED
- ---------------------------------------- ---------------------
<S> <C>
First................................... 5.0%
Second.................................. 4.0%
Third................................... 3.0%
Fourth.................................. 2.0%
Fifth................................... 2.0%
Sixth................................... 1.0%
Seventh and thereafter.................. None
</TABLE>

In the case of Class B shares of the Fund purchased on or after July 28,
1997 by Qualified Retirement Plans for which MSDW Trust serves as Trustee or
DWR's Retirement Plan Services serves as recordkeeper pursuant to a written
Recordkeeping Services Agreement, shares held for three years or more after
purchase (calculated as described in the paragraph above) will not be subject to
any CDSC upon redemption. However, shares redeemed earlier than three years
after purchase may be subject to a CDSC (calculated as described in the
paragraph above), the percentage of which will depend on how long the shares
have been held, as set forth in the following table:

<TABLE>
<CAPTION>
YEAR SINCE PURCHASE CDSC AS A PERCENTAGE
PAYMENT MADE OF AMOUNT REDEEMED
- ---------------------------------------- ---------------------
<S> <C>
First................................... 2.0%
Second.................................. 2.0%
Third................................... 1.0%
Fourth and thereafter................... None
</TABLE>

CDSC WAIVERS. A CDSC will not be imposed on: (i) any amount which represents an
increase in value of shares purchased within the six years (or, in the case of
shares held by certain Qualified Retirement Plans, three years) preceding the
redemption; (ii) the current net asset value of shares purchased more than six
years (or, in the case of shares held by certain Qualified Retirement Plans,
three years) prior to the redemption; and (iii) the current net asset value of
shares purchased through reinvestment of dividends or distributions and/or
shares acquired in exchange for shares of FSC Funds or of other Morgan Stanley
Dean Witter Funds acquired in exchange for such shares. Moreover, in determining
whether a CDSC is applicable it will be assumed that amounts described in (i),
(ii) and (iii) above (in that order) are redeemed first.

In addition, the CDSC, if otherwise applicable, will be waived in the case
of:

(1) redemptions of shares held at the time a shareholder dies or becomes
disabled, only if the shares are: (a) registered either in the name of an
individual shareholder (not a trust), or in the names of such shareholder and
his or her spouse as joint tenants with right of survivorship; or (b) held in a
qualified corporate or self-employed retirement plan, Individual Retirement
Account ("IRA") or Custodial Account under Section 403(b)(7) of the Internal
Revenue Code ("403(b) Custodial Account"), provided in either case that the
redemption is requested within one year of the death or initial determination of
disability;

(2) redemptions in connection with the following retirement plan
distributions: (a) lump-sum or other distributions from a qualified corporate
or self-employed retirement plan following retirement (or, in the case of a "key
employee" of a "top heavy" plan, following attainment of age 59 1/2); (b)
distributions from an IRA or 403(b) Custodial Account following attainment of
age 59 1/2; or (c) a tax-free return of an excess contribution to an IRA; and

(3) all redemptions of shares held for the benefit of a participant in a
Qualified Retirement Plan which offers investment companies managed by the
Investment Manager or its subsidiary, MSDW Services, as self-directed investment
alternatives and for which MSDW Trust serves as Trustee or DWR's Retirement Plan
Services serves as recordkeeper pursuant to a written Recordkeeping Services
Agreement ("Eligible Plan"), provided that either: (A) the plan continues to be
an Eligible Plan after the

17
<PAGE>
redemption; or (b) the redemption is in connection with the complete termination
of the plan involving the distribution of all plan assets to participants.

With reference to (1) above, for the purpose of determining disability, the
Distributor utilizes the definition of disability contained in Section 72(m)(7)
of the Internal Revenue Code, which relates to the inability to engage in
gainful employment. With reference to (2) above, the term "distribution" does
not encompass a direct transfer of IRA, 403(b) Custodial Account or retirement
plan assets to a successor custodian or trustee. All waivers will be granted
only following receipt by the Distributor of confirmation of the shareholder's
entitlement.

CONVERSION TO CLASS A SHARES. All shares of the Fund held prior to July 28,
1997 (other than shares held by certain employee benefit plans established by
DWR and its affiliate, SPS Transaction Services, Inc.) have been designated
Class B shares. Shares held before May 1, 1997 that have been designated Class B
shares will convert to Class A shares in May, 2007. In all other instances Class
B shares will convert automatically to Class A shares, based on the relative net
asset values of the shares of the two Classes on the conversion date, which will
be approximately ten (10) years after the date of the original purchase. The ten
year period is calculated from the last day of the month in which the shares
were purchased or, in the case of Class B shares acquired through an exchange or
a series of exchanges, from the last day of the month in which the original
Class B shares were purchased, provided that shares originally purchased before
May 1, 1997 will convert to Class A shares in May, 2007. The conversion of
shares purchased on or after May 1, 1997 will take place in the month following
the tenth anniversary of the purchase. There will also be converted at that time
such proportion of Class B shares acquired through automatic reinvestment of
dividends and distributions owned by the shareholder as the total number of his
or her Class B shares converting at the time bears to the total number of
outstanding Class B shares purchased and owned by the shareholder. In the case
of Class B shares held by a Qualified Retirement Plan for which MSDW Trust
serves as Trustee or DWR's Retirement Plan Services serves as recordkeeper
pursuant to a written Recordkeeping Services Agreement, the plan is treated as a
single investor and all Class B shares will convert to Class A shares on the
conversion date of the first shares of a Morgan Stanley Dean Witter Multi-Class
Fund purchased by that plan. In the case of Class B shares previously exchanged
for shares of an "Exchange Fund" (see "Shareholder Services--Exchange
Privilege"), the period of time the shares were held in the Exchange Fund
(calculated from the last day of the month in which the Exchange Fund shares
were acquired) is excluded from the holding period for conversion. If those
shares are subsequently re-exchanged for Class B shares of a Morgan Stanley Dean
Witter Multi-Class Fund, the holding period resumes on the last day of the month
in which Class B shares are reacquired.

If a shareholder has received share certificates for Class B shares, such
certificates must be delivered to the Transfer Agent at least one week prior to
the date for conversion. Class B shares evidenced by share certificates that are
not received by the Transfer Agent at least one week prior to any conversion
date will be converted into Class A shares on the next scheduled conversion date
after such certificates are received.

Effectiveness of the conversion feature is subject to the continuing
availability of a ruling of the Internal Revenue Service or an opinion of
counsel that (i) the conversion of shares does not constitute a taxable event
under the Internal Revenue Code, (ii) Class A shares received on conversion will
have a basis equal to the shareholder's basis in the converted Class B shares
immediately prior to the conversion, and (iii) Class A shares received on
conversion will have a holding period that includes the holding period of the
converted Class B shares. The conversion feature may be suspended if the ruling
or opinion is no longer available. In such event, Class B shares would continue
to be subject to Class B 12b-1 fees.

LEVEL LOAD ALTERNATIVE-- CLASS C SHARES

Class C shares are sold at net asset value next determined without an initial
sales charge but are subject to a CDSC of 1.0% on most redemptions made within
one year after purchase (calculated from the last day of the month in which the
shares were purchased). The CDSC will be assessed on an amount equal to the
lesser of the current market value or the cost of the shares being redeemed. The
CDSC will not be imposed in the circumstances set forth above in the section
"Contingent Deferred Sales Charge Alternative-- Class B Shares--CDSC Waivers,"
except that the references to six years in the first paragraph of that section
shall mean one year in the case of Class C shares. Class C shares are subject to
an annual 12b-1 fee of up to 0.75% of the average daily net assets of the Class.
Unlike Class B shares, Class C shares have no conversion feature and,
accordingly, an investor that purchases Class C shares will be subject to 12b-1
fees applicable to Class C shares for an indefinite period subject to annual
approval by the Fund's Board of Trustees and regulatory limitations.

NO LOAD ALTERNATIVE-- CLASS D SHARES

Class D shares are offered without any sales charge on purchase or redemption
and without any 12b-1 fee. Class D shares are offered only to investors meeting
an initial investment minimum of $5 million ($25 million for Qualified
Retirement Plans for which MSDW Trust serves as Trustee or DWR's Retirement Plan
Services serves as recordkeeper pursuant to a written Recordkeeping Services
Agreement) and the following categories of investors: (i) investors
participating in the MSDW Advisors mutual

18
<PAGE>
fund asset allocation program pursuant to which such persons pay an asset based
fee; (ii) persons participating in a fee-based program approved by the
Distributor, pursuant to which such persons pay an asset based fee for services
in the nature of investment advisory, administrative and/or brokerage services
(subject to all of the terms and conditions of such programs referred to in (i)
and (ii) above, which may include termination fees, mandatory redemption upon
termination and such other circumstances as specified in the programs'
agreements, and restrictions on transferability of Fund shares); (iii) 401(k)
plans established by DWR and SPS Transaction Services, Inc. (an affiliate of
DWR) for their employees; (iv) certain Unit Investment Trusts sponsored by DWR;
(v) certain other open-end investment companies whose shares are distributed by
the Distributor; and (vi) other categories of investors, at the discretion of
the Board, as disclosed in the then current prospectus of the Fund. Shares of
the Fund held by the employee benefit plans referred to in clause (iii) above
prior to July 28, 1997 have been designated Class D shares. Investors who
require a $5 million (or $25 million) minimum initial investment to qualify to
purchase Class D shares may satisfy that requirement by investing that amount in
a single transaction in Class D shares of the Fund and other Morgan Stanley Dean
Witter Multi-Class Funds, subject to the $1,000 minimum initial investment
required for that Class of the Fund. In addition, for the purpose of meeting the
$5 million (or $25 million) minimum investment amount, holdings of Class A
shares in all Morgan Stanley Dean Witter Multi-Class Funds, shares of FSC Funds
and shares of Morgan Stanley Dean Witter Funds for which such shares have been
exchanged will be included together with the current investment amount. If a
shareholder redeems Class A shares and purchases Class D shares, such redemption
may be a taxable event.

PLAN OF DISTRIBUTION

The Fund has adopted a Plan of Distribution pursuant to Rule 12b-1 under the Act
with respect to the distribution of Class A, Class B and Class C shares of the
Fund. In the case of Class A and Class C shares, the Plan provides that the Fund
will reimburse the Distributor and others for the expenses of certain activities
and services incurred by them specifically on behalf of those shares.
Reimbursements for these expenses will be made in monthly payments by the Fund
to the Distributor, which will in no event exceed amounts equal to payments at
the annual rates of 0.25% and 0.75% of the average daily net assets of Class A
and Class C, respectively. In the case of Class B shares, the Plan provides that
the Fund will pay the Distributor a fee, which is accrued daily and paid
monthly, at the annual rate of 0.75% (0.65% on amounts over $10 billion) of the
lesser of: (a) the average daily aggregate gross sales of the Fund's Class B
shares since the inception of the Fund (not including reinvestments of dividends
or capital gains distributions), less the average daily aggregate net asset
value of the Fund's Class B shares redeemed since the Fund's inception upon
which a CDSC has been imposed or waived, or (b) the average daily net assets of
Class B. The fee is treated by the Fund as an expense in the year it is accrued.
In the case of Class A shares, the entire amount of the fee currently represents
a service fee within the meaning of the NASD guidelines. In the case of Class B
and Class C shares, a portion of the fee payable pursuant to the Plan, equal to
0.20% and 0.25% of the average daily net assets of each of these Classes,
respectively, is currently characterized as a service fee. A service fee is a
payment made for personal service and/or the maintenance of shareholder
accounts.

Additional amounts paid under the Plan in the case of Class B and Class C
shares are paid to the Distributor for services provided and the expenses borne
by the Distributor and others in the distribution of the shares of those
Classes, including the payment of commissions for sales of the shares of those
Classes and incentive compensation to and expenses of Morgan Stanley Dean Witter
Financial Advisors and others who engage in or support distribution of shares or
who service shareholder accounts, including overhead and telephone expenses;
printing and distribution of prospectuses and reports used in connection with
the offering of the Fund's shares to other than current shareholders; and
preparation, printing and distribution of sales literature and advertising
materials. In addition, the Distributor may utilize fees paid pursuant to the
Plan in the case of Class B shares to compensate DWR and other Selected
Broker-Dealers for their opportunity costs in advancing such amounts, which
compensation would be in the form of a carrying charge on any unreimbursed
expenses.

For the fiscal year ended December 31, 1997, Class B shares of the Fund
accrued payments under the Plan amounting to $43,758,596, which amount is equal
to 0.75% of the average daily net assets of Class B for the fiscal year. These
payments were calculated pursuant to clause (b) of the compensation formula
under the Plan. All shares held prior to July 28, 1997 have been designated
Class B shares. For the fiscal period July 28, 1997 through December 31, 1997,
Class A and Class C shares of the Fund accrued payments under the Plan amounting
to $13,027 and $7,914, respectively, which amounts on an annualized basis are
equal to 0.25% and 0.75% of the average daily net assets of Class A and Class C,
respectively, for such period.

In the case of Class B shares, at any given time, the expenses in
distributing Class B shares of the Fund may be in excess of the total of (i) the
payments made by the Fund pursuant to the Plan, and (ii) the proceeds of CDSCs
paid by investors upon the redemption of Class B shares. For example, if $1
million in expenses in distributing Class B shares of the Fund had been incurred
and $750,000 had been received as described in (i) and (ii) above, the excess
expense would amount to $250,000. The Distributor has advised the Fund that such
excess amounts, including the carrying charge described above, totalled
$34,202,402 at

19
<PAGE>
December 31, 1997, which was equal to 0.63% of the net assets of Class B on such
date. Because there is no requirement under the Plan that the Distributor be
reimbursed for all distribution expenses or any requirement that the Plan be
continued from year to year, such excess amount does not constitute a liability
of the Fund. Although there is no legal obligation for the Fund to pay expenses
incurred in excess of payments made to the Distributor under the Plan, and the
proceeds of CDSCs paid by investors upon redemption of shares, if for any reason
the Plan is terminated the Trustees will consider at that time the manner in
which to treat such expenses. Any cumulative expenses incurred, but not yet
recovered through distribution fees or CDSCs, may or may not be recovered
through future distribution fees or CDSCs.

In the case of Class A and Class C shares, expenses incurred pursuant to the
Plan in any calendar year in excess of 0.25% or 0.75% of the average daily net
assets of Class A or Class C, respectively, will not be reimbursed by the Fund
through payments in any subsequent year, except that expenses representing a
gross sales commission credited to Morgan Stanley Dean Witter Financial Advisors
and other Selected Broker-Dealer representatives at the time of sale may be
reimbursed in the subsequent calendar year. The Distributor has advised the Fund
that unreimbursed expenses representing a gross sales commission credited to
account executives at the time of sale totalled $39,501 in the case of Class C
at December 31, 1997, which amount was equal to 0.90% of the net assets of Class
C on such date, and that there were no such expenses that may be reimbursed in
the subsequent year in the case of Class A on such date. No interest or other
financing charges will be incurred on any Class A or Class C distribution
expenses incurred by the Distributor under the Plan or on any unreimbursed
expenses due to the Distributor pursuant to the Plan.

DETERMINATION OF NET ASSET VALUE

The net asset value per share is determined once daily at 4:00 p.m., New York
time (or, on days when the New York Stock Exchange closes prior to 4:00 p.m., at
such earlier time), on each day that the New York Stock Exchange is open by
taking the net assets of the Fund, dividing by the number of shares outstanding
and adjusting to the nearest cent. The assets belonging to the Class A, Class B,
Class C and Class D shares will be invested together in a single portfolio. The
net asset value of each Class, however, will be determined separately by
subtracting each Class's accrued expenses and liabilities. The net asset value
per share will not be determined on Good Friday and on such other federal and
non-federal holidays as are observed by the New York Stock Exchange.

In the calculation of the Fund's net asset value: (1) all portfolio
securities for which over-the-counter market quotations are readily available
are valued at the bid price; (2) when market quotations are not readily
available, including circumstances under which it is determined by the
Investment Manager that sale or bid prices are not reflective of a security's
market value, portfolio securities are valued at their fair value as determined
in good faith under procedures established by and under the general supervision
of the Fund's Board of Trustees (valuation of securities for which market
quotations are not readily available may be based upon current market prices of
securities which are comparable in coupon, rating and maturity or an appropriate
matrix utilizing similar factors); and (3) short-term instruments having a
maturity date of more than sixty days are valued on a "mark-to-market" basis,
that is, at prices based on market quotations for securities of similar type,
yield, quality and maturity, until sixty days prior to maturity and thereafter
at amortized cost. Short-term instruments having a maturity date of sixty days
or less at the time of purchase are valued at amortized cost unless the Board of
Trustees determines this does not represent fair market value.

Certain of the Fund's portfolio securities may be valued by an outside
pricing service approved by the Fund's Trustees. The pricing service may utilize
a matrix system incorporating security quality, maturity and coupon as the
evaluation model parameters, and/or research evaluations by its staff, including
review of broker-dealer market price quotations, in determining what it believes
is the fair valuation of the portfolio securities valued by such pricing
service.

SHAREHOLDER SERVICES
- --------------------------------------------------------------------------------

AUTOMATIC INVESTMENT OF DIVIDENDS AND DISTRIBUTIONS. All dividends and capital
gains distributions are automatically paid in full and fractional shares of the
applicable Class of the Fund (or, if specified by the shareholder, in shares of
any other open-end Morgan Stanley Dean Witter Fund), unless the shareholder
requests that they be paid in cash. Shares so acquired are acquired at net asset
value and are not subject to the imposition of a front-end sales charge or a
CDSC (see "Redemptions and Repurchases"). Such dividends and distributions will
be paid, at the net asset value per share, in shares of the applicable Class of
the Fund (or in cash if the shareholder so requests) on the monthly payment
date, which generally will be no later than the last business day of the month
for which the dividend or distribution is payable. Processing of dividend checks
begins immediately following the monthly payment date. Shareholders who have
requested to receive dividends in cash will normally receive their monthly
dividend check during the first ten days of the following month.

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<PAGE>
INVESTMENT OF DIVIDENDS AND DISTRIBUTIONS RECEIVED IN CASH. Any shareholder who
receives a cash payment representing a dividend or capital gains distribution
may invest such dividend or distribution in shares of the applicable Class at
the net asset value per share next determined after receipt by the Transfer
Agent, by returning the check or the proceeds to the Transfer Agent within
thirty days after the payment date. Shares so acquired are acquired at net asset
value and are not subject to the imposition of a front-end sales charge or a
CDSC (see "Redemptions and Repurchases").

EASYINVEST-SM-. Shareholders may subscribe to EasyInvest, an automatic purchase
plan which provides for any amount from $100 to $5,000 to be transferred
automatically from a checking or savings account or following redemption of
shares of a Morgan Stanley Dean Witter money market fund, on a semi-monthly,
monthly or quarterly basis, to the Transfer Agent for investment in shares of
the Fund (see "Purchase of Fund Shares" and "Redemptions and
Repurchases--Involuntary Redemption").

SYSTEMATIC WITHDRAWAL PLAN. A systematic withdrawal plan (the "Withdrawal
Plan") is available for shareholders who own or purchase shares of the Fund
having a minimum value of $10,000 based upon the then current net asset value.
The Withdrawal Plan provides for monthly or quarterly (March, June, September
and December) checks in any dollar amount, not less than $25, or in any whole
percentage of the account balance, on an annualized basis. Any applicable CDSC
will be imposed on shares redeemed under the Withdrawal Plan (See "Purchase of
Fund Shares"). Therefore, any shareholder participating in the Withdrawal Plan
will have sufficient shares redeemed from his or her account so that the
proceeds (net of any applicable CDSC) to the shareholder will be the designated
monthly or quarterly amount. Withdrawal plan payments should not be considered
as dividends, yields or income. If periodic withdrawal plan payments
continuously exceed net investment income and net capital gains, the
shareholder's original investment will be correspondingly reduced and ultimately
exhausted. Each withdrawal constitutes a redemption of shares and any gain or
loss realized must be recognized for federal income tax purposes.

Shareholders should contact their Morgan Stanley Dean Witter Financial
Advisor or other Selected Broker-Dealer representative or the Transfer Agent for
further information about any of the above services.

TAX SHELTERED RETIREMENT PLANS. Retirement plans are available for use by
corporations, the self-employed, Individual Retirement Accounts and Custodial
Accounts under Section 403(b)(7) of the Internal Revenue Code. Adoption of such
plans should be on advice of legal counsel or tax advisor.

For further information regarding plan administration, custodial fees and
other details, investors should contact their Morgan Stanley Dean Witter
Financial Advisor or other Selected Broker-Dealer representative or the Transfer
Agent.

EXCHANGE PRIVILEGE

Shares of each Class may be exchanged for shares of the same Class of any other
Morgan Stanley Dean Witter Multi-Class Fund without the imposition of any
exchange fee. Shares may also be exchanged for shares of the following funds:
Morgan Stanley Dean Witter Short-Term U.S. Treasury Trust, Morgan Stanley Dean
Witter Limited Term Municipal Trust, Morgan Stanley Dean Witter Short-Term Bond
Fund, and five Morgan Stanley Dean Witter Funds which are money market funds
(the "Exchange Funds"). Class A shares may also be exchanged for shares of
Morgan Stanley Dean Witter Multi-State Municipal Series Trust and Morgan Stanley
Dean Witter Hawaii Municipal Trust, which are Morgan Stanley Dean Witter Funds
sold with a front-end sales charge ("FSC Funds"). Class B shares may also be
exchanged for shares of Morgan Stanley Dean Witter Global Short-Term Income Fund
Inc. ("Global Short-Term"), which is a Morgan Stanley Dean Witter Fund offered
with a CDSC. Exchanges may be made after the shares of the Fund acquired by
purchase (not by exchange or dividend reinvestment) have been held for thirty
days. There is no waiting period for exchanges of shares acquired by exchange or
dividend reinvestment.

An exchange to another Morgan Stanley Dean Witter Multi-Class Fund, any FSC
Fund, Global Short-Term or any Exchange Fund that is not a money market fund is
on the basis of the next calculated net asset value per share of each fund after
the exchange order is received. When exchanging into a money market fund from
the Fund, shares of the Fund are redeemed out of the Fund at their next
calculated net asset value and the proceeds of the redemption are used to
purchase shares of the money market fund at their net asset value determined the
following day. Subsequent exchanges between any of the money market funds and
any of the Morgan Stanley Dean Witter Multi-Class Funds, FSC Funds, Global
Short-Term or any Exchange Fund that is not a money market fund can be effected
on the same basis.

No CDSC is imposed at the time of any exchange of shares, although any
applicable CDSC will be imposed upon ultimate redemption. During the period of
time the shareholder remains in an Exchange Fund (calculated from the last day
of the month in which the Exchange Fund shares were acquired), the holding
period (for the purpose of determining the rate of the CDSC) is frozen. If those
shares are subsequently re-exchanged for shares of a Morgan Stanley Dean Witter
Multi-Class Fund or shares of Global Short-Term, the holding period previously
frozen when the first exchange was made resumes on the last day of the month in
which shares of a Morgan Stanley Dean Witter Multi-Class Fund or shares of
Global Short-Term are reacquired. Thus, the CDSC is based upon the time
(calculated as described above) the shareholder was invested in shares of a
Morgan Stanley Dean Witter Multi-Class Fund or in

21
<PAGE>
shares of Global Short-Term (see "Purchase of Fund Shares"). In the case of
exchanges of Class A shares which are subject to a CDSC, the holding period also
includes the time (calculated as described above) the shareholder was invested
in shares of a FSC Fund. In the case of shares exchanged into an Exchange Fund
on or after April 23, 1990, upon a redemption of shares which results in a CDSC
being imposed, a credit (not to exceed the amount of the CDSC) will be given in
an amount equal to the Exchange Fund 12b-1 distribution fees incurred on or
after that date which are attributable to those shares. (Exchange Fund 12b-1
distribution fees are described in the prospectuses for those funds.) Class B
shares of the Fund acquired in exchange for shares of Global Short-Term or Class
B shares of another Morgan Stanley Dean Witter Multi-Class Fund having a
different CDSC schedule than that of this Fund will be subject to the higher
CDSC schedule, even if such shares are subsequently re-exchanged for shares of
the fund with the lower CDSC schedule.

ADDITIONAL INFORMATION REGARDING EXCHANGES. Purchases and exchanges should be
made for investment purposes only. A pattern of frequent exchanges may be deemed
by the Investment Manager to be abusive and contrary to the best interests of
the Fund's other shareholders and, at the Investment Manager's discretion, may
be limited by the Fund's refusal to accept additional purchases and/or exchanges
from the investor. Although the Fund does not have any specific definition of
what constitutes a pattern of frequent exchanges, and will consider all relevant
factors in determining whether a particular situation is abusive and contrary to
the best interests of the Fund and its other shareholders, investors should be
aware that the Fund and each of the other Morgan Stanley Dean Witter Funds may
in their discretion limit or otherwise restrict the number of times this
Exchange Privilege may be exercised by any investor. Any such restriction will
be made by the Fund on a prospective basis only, upon notice to the shareholder
not later than ten days following such shareholder's most recent exchange. Also,
the Exchange Privilege may be terminated or revised at any time by the Fund
and/or any of such Morgan Stanley Dean Witter Funds for which shares of the Fund
have been exchanged, upon such notice as may be required by applicable
regulatory agencies. Shareholders maintaining margin accounts with DWR or
another Selected Broker-Dealer are referred to their Morgan Stanley Dean Witter
Financial Advisor or other Selected Broker-Dealer representative regarding
restrictions on exchange of shares of the Fund pledged in the margin account.

The current prospectus for each fund describes its investment objective(s)
and policies, and shareholders should obtain a copy and examine it carefully
before investing. Exchanges are subject to the minimum investment requirement of
each Class of Shares and any other conditions imposed by each fund. In the case
of a shareholder holding a share certificate or certificates, no exchanges may
be made until all applicable share certificates have been received by the
Transfer Agent and deposited in the shareholder's account. An exchange will be
treated for federal income tax purposes the same as a repurchase or redemption
of shares, on which the shareholder may realize a capital gain or loss. However,
the ability to deduct capital losses on an exchange may be limited in situations
where there is an exchange of shares within ninety days after the shares are
purchased. The Exchange Privilege is only available in states where an exchange
may legally be made.

If DWR or another Selected Broker-Dealer is the current dealer of record and
its account numbers are part of the account information, shareholders may
initiate an exchange of shares of the Fund for shares of any of the Morgan
Stanley Dean Witter Funds (for which the Exchange Privilege is available)
pursuant to this Exchange Privilege by contacting their Morgan Stanley Dean
Witter Financial Advisor or other Selected Broker-Dealer representative (no
Exchange Privilege Authorization Form is required). Other shareholders (and
those shareholders who are clients of DWR or another Selected Broker-Dealer but
who wish to make exchanges directly by writing or telephoning the Transfer
Agent) must complete and forward to the Transfer Agent an Exchange Privilege
Authorization Form, copies of which may be obtained from the Transfer Agent, to
initiate an exchange. If the Authorization Form is used, exchanges may be made
in writing or by contacting the Transfer Agent at (800) 869-NEWS (toll-free).

The Fund will employ reasonable procedures to confirm that exchange
instructions communicated over the telephone are genuine. Such procedures may
include requiring various forms of personal identification such as name, mailing
address, social security or other tax identification number and DWR or other
Selected Broker-Dealer account number (if any). Telephone instructions may also
be recorded. If such procedures are not employed, the Fund may be liable for any
losses due to unauthorized or fraudulent instructions.

Telephone exchange instructions will be accepted if received by the Transfer
Agent between 9:00 a.m. and 4:00 p.m., New York time, on any day the New York
Stock Exchange is open. Any shareholder wishing to make an exchange who has
previously filed an Exchange Privilege Authorization Form and who is unable to
reach the Fund by telephone should contact his or her Morgan Stanley Dean Witter
Financial Advisor or other Selected Broker-Dealer representative, if
appropriate, or make a written exchange request. Shareholders are advised that
during periods of drastic economic or market changes, it is possible that the
telephone exchange procedures may be difficult to implement, although this has
not been the case with the Morgan Stanley Dean Witter Funds in the past.

For further information regarding the Exchange Privilege, shareholders
should contact their Morgan Stanley Dean Witter Financial Advisor or other
Selected Broker-Dealer representative or the Transfer Agent.

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<PAGE>
REDEMPTIONS AND REPURCHASES
- --------------------------------------------------------------------------------

REDEMPTION. Shares of each Class of the Fund can be redeemed for cash at any
time at the net asset value per share next determined less the amount of any
applicable CDSC in the case of Class A, Class B or Class C shares (see "Purchase
of Fund Shares"). If shares are held in a shareholder's account without a share
certificate, a written request for redemption to the Fund's Transfer Agent at
P.O. Box 983, Jersey City, NJ 07303 is required. If certificates are held by the
shareholder, the shares may be redeemed by surrendering the certificates with a
written request for redemption, along with any additional information required
by the Transfer Agent.

REPURCHASE. DWR and other Selected Broker-Dealers are authorized to repurchase
shares represented by a share certificate which is delivered to any of their
offices. Shares held in a shareholder's account without a share certificate may
also be repurchased by DWR and other Selected Broker-Dealers upon the telephonic
request of the shareholder. The repurchase price is the net asset value next
computed (see "Purchase of Fund Shares") after such repurchase order is received
by DWR or other Selected Broker-Dealer reduced by any applicable CDSC.

The CDSC, if any, will be the only fee imposed upon repurchase by the Fund
or the Distributor. The offer by DWR and other Selected Broker-Dealers to
repurchase shares may be suspended without notice by them at any time. In that
event, shareholders may redeem their shares through the Fund's Transfer Agent as
set forth above under "Redemption."

PAYMENT FOR SHARES REDEEMED OR REPURCHASED. Payment for shares presented for
repurchase or redemption will be made by check within seven days after receipt
by the Transfer Agent of the certificate and/or written request in good order.
Such payment may be postponed or the right of redemption suspended under unusual
circumstances, e.g., when normal trading is not taking place on the New York
Stock Exchange. If the shares to be redeemed have recently been purchased by
check, payment of the redemption proceeds may be delayed for the minimum time
needed to verify that the check used for investment has been honored (not more
than fifteen days from the time of receipt of the check by the Transfer Agent).
Shareholders maintaining margin accounts with DWR or another Selected
Broker-Dealer are referred to their Morgan Stanley Dean Witter Financial Advisor
or other Selected Broker-Dealer representative regarding restrictions on
redemption of shares of the Fund pledged in the margin account.

REINSTATEMENT PRIVILEGE. A shareholder who has had his or her shares redeemed
or repurchased and has not previously exercised this reinstatement privilege
may, within 35 days after the date of the redemption or repurchase, reinstate
any portion or all of the proceeds of such redemption or repurchase in shares of
the Fund in the same Class from which such shares were redeemed or repurchased,
at their net asset value next determined after a reinstatement request, together
with the proceeds, is received by the Transfer Agent and receive a pro rata
credit for any CDSC paid in connection with such redemption or repurchase.

INVOLUNTARY REDEMPTION. The Fund reserves the right, on sixty days' notice, to
redeem, at their net asset value, the shares of any shareholder (other than
shares held in an Individual Retirement Account or Custodial Account under
Section 403(b)(7) of the Internal Revenue Code) whose shares due to redemptions
by the shareholder have a value of less than $100, or such lesser amount as may
be fixed by the Trustees or, in the case of an account opened through
EasyInvest, if after twelve months the shareholder has invested less than $1,000
in the account. However, before the Fund redeems such shares and sends the
proceeds to the shareholder, it will notify the shareholder that the value of
the shares is less than the applicable amount and allow the shareholder sixty
days to make an additional investment in an amount which will increase the value
of his or her account to at least the applicable amount before the redemption is
processed. No CDSC will be imposed on any involuntary redemption.

DIVIDENDS, DISTRIBUTIONS AND TAXES
- --------------------------------------------------------------------------------

DIVIDENDS AND DISTRIBUTIONS. The Fund declares dividends separately for each
Class of shares from net investment income on each day the New York Stock
Exchange is open for business to shareholders of record as of the close of
business the preceding business day. The amount of dividend may fluctuate from
day to day. Such dividends are paid monthly. The Fund intends to distribute
substantially all of its net investment income on an annual basis.

The Fund may distribute quarterly net realized short-term capital gains, if
any, in excess of any net realized long-term capital losses. The Fund intends to
distribute dividends from net long-term capital gains, if any, at least once
each year. The Fund may, however, elect to retain all or a portion of any net
long-term capital gains in any year for reinvestment.

All dividends and any capital gains distributions will be paid in additional
shares of the same Class and automatically credited to the shareholder's account
without issuance of a share certificate unless the shareholder requests in
writing that all dividends or all dividends and distributions be paid in cash.
Shares acquired by dividend and distribution reinvestments will not be subject
to any front-end sales

23
<PAGE>
charge or CDSC. Class B shares acquired through dividend and distribution
reinvestments will become eligible for conversion to Class A shares on a pro
rata basis. Distributions paid on Class A and Class D shares will be higher than
for Class B and Class C shares because distribution fees paid by Class B and
Class C shares are higher. (See "Shareholder Services--Automatic Investment of
Dividends and Distributions.")

TAXES. Because the Fund intends to distribute substantially all of its net
investment income and net short-term capital gains to shareholders and continue
to qualify as a regulated investment company under Subchapter M of the Internal
Revenue Code, it is not expected that the Fund will be required to pay any
federal income tax on such income and capital gains.

Shareholders who are required to pay taxes on their income will normally
have to pay federal income taxes, and any applicable state and/or local income
taxes, on the dividends and distributions they receive from the Fund. Such
dividends and distributions, to the extent that they are derived from net
investment income and net short-term capital gains, are taxable to the
shareholder as ordinary dividend income regardless of whether the shareholder
receives such distributions in additional shares or in cash. Any dividends
declared in the last quarter of any calendar year which are paid in the
following year prior to February 1 will be deemed, for tax purposes, to have
been received by the shareholder in the prior year.

Any dividends declared in the last quarter of any calendar year which are
paid in the following calendar year prior to February 1 will be deemed, for tax
purposes, to have been received by the shareholder in the prior calendar year.

Distributions of net long-term capital gains, if any, are taxable to
shareholders as long-term capital gains regardless of how long a shareholder has
held the Fund's shares and regardless of whether the distribution is received in
additional shares or in cash. Capital gains distributions are not eligible for
the corporate dividends received deduction.

The Fund may at times make payments from sources other than income or net
capital gains. Payments from such sources would, in effect, represent a return
of a portion of each shareholder's investment. All, or a portion, of such
payments would not be taxable to shareholders.

After the end of the calendar year, shareholders will be sent full
information on their dividends and capital gains distributions for tax purposes.
Shareholders will also be notified of their proportionate share of long-term
capital gains distributions that are eligible for a reduced rate of tax under
the Taxpayer Relief Act of 1997.

To avoid being subject to a 31% federal backup withholding tax on taxable
dividends, capital gains distributions and the proceeds of redemptions and
repurchases, shareholders' taxpayer identification numbers must be furnished and
certified as to accuracy.

The foregoing discussion relates solely to the federal income tax
consequences of an investment in the Fund. Distributions may also be subject to
state and local taxes; therefore, each shareholder is advised to consult his or
her own tax advisor.

PERFORMANCE INFORMATION
- --------------------------------------------------------------------------------

From time to time the Fund may quote its "yield" and/or its "total return" in
advertisements and sales literature. These figures are computed separately for
Class A, Class B, Class C and Class D shares. Both the yield and the total
return of the Fund are based on historical earnings and are not intended to
indicate future performance. The yield of each Class of the Fund is computed by
dividing the Class's net investment income over a 30-day period by an average
value (using the average number of shares entitled to receive dividends and the
maximum offering price per share at the end of the period), all in accordance
with applicable regulatory requirements. Such amount is compounded for six
months and then annualized for a twelve-month period to derive the Fund's yield
for each Class.

The "average annual total return" of the Fund refers to a figure reflecting
the average annualized percentage increase (or decrease) in the value of an
initial investment in a Class of the Fund of $1,000 over periods of one, five
and ten years. Average annual total return reflects all income earned by the
Fund, any appreciation or depreciation of the Fund's assets, all expenses
incurred by the applicable Class and all sales charges which would be incurred
by shareholders, for the stated periods. It also assumes reinvestment of all
dividends and distributions paid by the Fund.

In addition to the foregoing, the Fund may advertise its total return for each
Class over different periods of time by means of aggregate, average, and
year-by-year or other types of total return figures. Such calculations may or
may not reflect the deduction of any sales charge which, if reflected, would
reduce the performance quoted. The Fund may also advertise the growth of
hypothetical investments of $10,000, $50,000 and $100,000 in each Class of
shares of the Fund. The Fund from time to time may also advertise its
performance relative to certain performance rankings and indexes compiled by
independent organizations.

24
<PAGE>
ADDITIONAL INFORMATION
- --------------------------------------------------------------------------------

VOTING RIGHTS. All shares of beneficial interest of the Fund are of $0.01 par
value and are equal as to earnings, assets and voting privileges except that
each Class will have exclusive voting privileges with respect to matters
relating to distribution expenses borne solely by such Class or any other matter
in which the interests of one Class differ from the interests of any other
Class. In addition, Class B shareholders will have the right to vote on any
proposed material increase in Class A's expenses, if such proposal is submitted
separately to Class A shareholders. Also, as discussed herein, Class A, Class B
and Class C bear the expenses related to the distribution of their respective
shares.

The Fund is not required to hold Annual Meetings of Shareholders and in
ordinary circumstances the Fund does not intend to hold such meetings. The
Trustees may call Special Meetings of Shareholders for action by shareholder
vote as may be required by the Act or the Declaration of Trust. Under certain
circumstances the Trustees may be removed by action of the Trustees or by the
shareholders.

Under Massachusetts law, shareholders of a business trust may, under certain
circumstances, be held personally liable as partners for the obligations of the
Fund. However, the Declaration of Trust contains an express disclaimer of
shareholder liability for acts or obligations of the Fund, requires that Fund
obligations include such disclaimer, and provides for indemnification and
reimbursement of expenses out of the Fund's property for any shareholder held
personally liable for the obligations of the Fund. Thus, the risk of a
shareholder incurring financial loss on account of shareholder liability is
limited to circumstances in which the Fund itself would be unable to meet its
obligations. Given the above limitations on shareholder personal liability, and
the nature of the Fund's assets and operations, the possibility of the Fund
being unable to meet its obligations is remote and, in the opinion of
Massachusetts counsel to the Fund, the risk to Fund shareholders of personal
liability is remote.

CODE OF ETHICS. Directors, officers and employees of MSDW Advisors, MSDW
Services and MSDW Distributors are subject to a strict Code of Ethics adopted by
those companies. The Code of Ethics is intended to ensure that the interests of
shareholders and other clients are placed ahead of any personal interest, that
no undue personal benefit is obtained from a person's employment activities and
that actual and potential conflicts of interest are avoided. To achieve these
goals and comply with regulatory requirements, the Code of Ethics requires,
among other things, that personal securities transactions by employees of the
companies be subject to an advance clearance process to monitor that no Morgan
Stanley Dean Witter Fund is engaged at the same time in a purchase or sale of
the same security. The Code of Ethics bans the purchase of securities in an
initial public offering, and also prohibits engaging in futures and options
transactions and profiting on short-term trading (that is, a purchase within
sixty days of a sale or a sale within sixty days of a purchase) of a security.
In addition, investment personnel may not purchase or sell a security for their
personal account within thirty days before or after any transaction in any
Morgan Stanley Dean Witter Fund managed by them. Any violations of the Code of
Ethics are subject to sanctions, including reprimand, demotion or suspension or
termination of employment. The Code of Ethics comports with regulatory
requirements and the recommendations in the 1994 report by the Investment
Company Institute Advisory Group on Personal Investing.

MASTER/FEEDER CONVERSION. The Fund reserves the right to seek to achieve its
investment objective by investing all of its investable assets in a diversified,
open-end management investment company having the same investment objective and
policies and substantially the same investment restrictions as those applicable
to the Fund.

SHAREHOLDER INQUIRIES. All inquiries regarding the Fund should be directed to
the Fund at the telephone numbers or address set forth on the front cover of
this Prospectus.

25
<PAGE>
MORGAN STANLEY DEAN WITTER
U.S. GOVERNMENT SECURITIES TRUST
TWO WORLD TRADE CENTER
NEW YORK, NEW YORK 10048

TRUSTEES
Michael Bozic
Charles A. Fiumefreddo
Edwin J. Garn
John R. Haire
Wayne E. Hedien
Dr. Manuel H. Johnson
Michael E. Nugent
Philip J. Purcell
John L. Schroeder

OFFICERS
Charles A. Fiumefreddo
Chairman and Chief Executive Officer
Barry Fink
Vice President, Secretary and
General Counsel
Rajesh K. Gupta
Vice President
Thomas F. Caloia
Treasurer

CUSTODIAN
The Bank of New York
90 Washington Street
New York, New York 10286

TRANSFER AGENT AND
DIVIDEND DISBURSING AGENT
Morgan Stanley Dean Witter Trust FSB
Harborside Financial Center
Plaza Two
Jersey City, New Jersey 07311

INDEPENDENT ACCOUNTANTS
PricewaterhouseCoopers LLP
1177 Avenue of the Americas
New York, New York 10036

INVESTMENT MANAGER
Morgan Stanley Dean Witter Advisors Inc.