WITTER DEAN U S GOVERNMENT SECURITIES TRUST
497, 1997-07-30
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<PAGE>
              PROSPECTUS
              JULY 28, 1997
 
              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. Except as discussed herein, shares of
the Fund held prior to July 28, 1997 have been designated Class B shares. 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 July 28, 1997, 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.
 
     DEAN WITTER DISTRIBUTORS INC.
      DISTRIBUTOR
 
      TABLE OF CONTENTS
 
   
Prospectus Summary/2
Summary of Fund Expenses/4
Financial Highlights/6
The Fund and its Management/7
Investment Objective and Policies/7
  Risk Considerations/11
Purchase of Fund Shares/13
Shareholder Services/23
Redemptions and Repurchases/26
Dividends, Distributions and Taxes/27
Performance Information/28
Additional Information/29
    
 
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.
 
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.
 
    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)
<PAGE>
PROSPECTUS SUMMARY
- --------------------------------------------------------------------------------
 
   
<TABLE>
<S>               <C>
The               The Fund is organized as a Trust, commonly known as a Massachusetts business trust, and is an
Fund              open-end diversified management investment company investing in obligations issued or guaranteed by
                  the U.S. Government.
- ----------------------------------------------------------------------------------------------------------------------
Shares Offered    Shares of beneficial interest with $0.01 par value (see page 29). The Fund offers four Classes of
                  shares, each with a different combination of sales charges, ongoing fees and other features (see
                  pages 13-23).
- ----------------------------------------------------------------------------------------------------------------------
Minimum           The minimum initial investment for each Class is $1,000 ($100 if the account is opened through
Purchase          EasyInvest-SM-). Class D shares are only available to persons investing $5 million or more and to
                  certain other limited categories of investors. For the purpose of meeting the minimum $5 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 Dean
                  Witter InterCapital Inc. serves as investment manager ("Dean Witter Funds") that are sold with a
                  front-end sales charge, and concurrent investments in Class D shares of the Fund and other Dean
                  Witter Funds that are multiple class funds, will be aggregated. The minimum subsequent investment is
                  $100 (see page 13).
- ----------------------------------------------------------------------------------------------------------------------
Investment        The investment objective of the Fund is high current income consistent with safety of principal.
Objective
- ----------------------------------------------------------------------------------------------------------------------
Investment        Dean Witter InterCapital Inc., the Investment Manager of the Fund, and its wholly-owned subsidiary,
Manager           Dean Witter Services Company Inc., serve in various investment management, advisory, management and
                  administrative capacities to 100 investment companies and other portfolios with assets of
                  approximately $96.6 billion at June 30, 1997 (see page 7).
- ----------------------------------------------------------------------------------------------------------------------
Management        The Investment Manager receives a monthly fee at the annual rate of 0.50% (1/2 of 1%) of daily net
Fee               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 7).
- ----------------------------------------------------------------------------------------------------------------------
Distributor       Dean Witter Distributors Inc. (the "Distributor"). The Fund has adopted a distribution plan pursuant
and               to Rule 12b-1 under the Investment Company Act (the "12b-1 Plan") with respect to the distribution
Distribution      fees paid by the Class A, Class B and Class C shares of the Fund to the Distributor. The entire
Fee               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 13 and 21).
- ----------------------------------------------------------------------------------------------------------------------
Alternative       Four classes of shares are offered:
Purchase
Arrangements      - Class A shares are offered with a front-end sales charge, starting at 4.25% and 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 13, 16 and 21).
</TABLE>
    
 
                                       2
<PAGE>
- --------------------------------------------------------------------------------
 
   
<TABLE>
<S>               <C>
                  - 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 13, 18
                  and 21).
                  - 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 13 and 21).
                  - Class D shares are offered only to investors meeting an initial investment minimum of $5 million
                  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 13 and 21).
- ----------------------------------------------------------------------------------------------------------------------
Dividends         Dividends from net investment income are declared daily and paid monthly and distributions from net
and               capital gains, if any, are paid at least once per year. The Fund may, however, determine to retain
Capital Gains     all or part of any net long-term capital gains in any year for reinvestment. Dividends and capital
Distributions     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 23
                  and 27).
- ----------------------------------------------------------------------------------------------------------------------
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 26).
- ----------------------------------------------------------------------------------------------------------------------
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 7-12).
- ----------------------------------------------------------------------------------------------------------------------
</TABLE>
    
 
  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
- --------------------------------------------------------------------------------
 
    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, 1996.
 
<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.................................................................   0.42%       0.42%     0.42%       0.42%
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)...............................................   0.75%       1.25%     1.25%       0.50%
</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 THE
    DATE OF THIS  PROSPECTUS. ACCORDINGLY, "TOTAL  FUND OPERATING EXPENSES,"  AS
    SHOWN  ABOVE WITH RESPECT TO THOSE CLASSES,  ARE BASED UPON THE SUM OF 12b-1
    FEES, MANAGEMENT FEES AND ESTIMATED "OTHER EXPENSES."
 
                                       4
<PAGE>
- --------------------------------------------------------------------------------
 
<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  $      65  $      82   $     132
    Class B...................................................................  $      63  $      70  $      89   $     151
    Class C...................................................................  $      23  $      40  $      69   $     151
    Class D...................................................................  $       5  $      16  $      28   $      63
 
You would pay the following expenses on the same $1,000 investment assuming no
redemption at the end of the period:
    Class A...................................................................  $      50  $      65  $      82   $     132
    Class B...................................................................  $      13  $      40  $      69   $     151
    Class C...................................................................  $      13  $      40  $      69   $     151
    Class D...................................................................  $       5  $      16  $      28   $      63
</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.
    
 
                                       5
<PAGE>
FINANCIAL HIGHLIGHTS
- --------------------------------------------------------------------------------
 
    The  following ratios and per share data  for a share of beneficial interest
outstanding throughout each period  have been audited  by Price Waterhouse  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. 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.
 
<TABLE>
<CAPTION>
                                                            FOR THE YEAR ENDED DECEMBER 31,
                           -------------------------------------------------------------------------------------------------
                            1996      1995      1994      1993      1992      1991      1990      1989      1988      1987
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
<S>                        <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>       <C>
PER SHARE OPERATING
 PERFORMANCE:
  Net asset value,
   beginning of period...   $ 9.21    $ 8.41    $ 9.31    $ 9.30    $ 9.52    $ 9.37    $ 9.51    $ 9.42    $ 9.75    $10.33
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
  Net investment
   income................     0.56      0.57      0.58      0.64      0.74      0.87      0.90      0.91      0.97      0.96
  Net realized and
   unrealized gain
   (loss)................    (0.29)     0.80     (0.90)     0.01     (0.22)     0.15     (0.14)     0.09     (0.33)    (0.58)
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
  Total from investment
   operations............     0.27      1.37     (0.32)     0.65      0.52      1.02      0.76      1.00      0.64      0.38
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
  Less dividends from net
   investment income.....    (0.56)    (0.57)    (0.58)    (0.64)    (0.74)    (0.87)    (0.90)    (0.91)    (0.97)    (0.96)
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
  Net asset value, end of
   period................   $ 8.92    $ 9.21    $ 8.41    $ 9.31    $ 9.30    $ 9.52    $ 9.37    $ 9.51    $ 9.42    $ 9.75
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
                           -------   -------   -------   -------   -------   -------   -------   -------   -------   -------
TOTAL INVESTMENT
 RETURN+.................    3.16%    16.74%   (3.51)%     7.13%     5.76%    11.43%     8.49%    11.10%     6.74%     3.92%
  Ratios to average net
   assets:
    Expenses.............    1.25%     1.24%     1.22%     1.18%     1.20%     1.17%     1.23%     1.19%     1.21%     1.18%
    Net investment
     income..............    6.28%     6.44%     6.57%     6.78%     7.91%     9.23%     9.60%     9.62%    10.01%     9.63%
SUPPLEMENTAL DATA:
  Net assets, end of
   period, in millions...   $6,450    $7,955    $8,211   $12,235   $12,484   $11,736    $9,829   $10,167   $10,366   $10,418
  Portfolio turnover
   rate..................       8%       14%       26%       32%       40%      104%       54%       44%       15%       51%
</TABLE>
 
- -------------
+ DOES  NOT REFLECT THE DEDUCTION  OF SALES CHARGE. CALCULATED  BASED ON THE NET
  ASSET VALUE AS OF THE LAST BUSINESS DAY OF THE PERIOD.
 
                                       6
<PAGE>
THE FUND AND ITS MANAGEMENT
- --------------------------------------------------------------------------------
 
    Dean Witter U.S.  Government Securities  Trust (the "Fund")  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.
 
    Dean Witter InterCapital Inc. ("InterCapital" 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, which  was incorporated  in July,
1992, is a wholly-owned  subsidiary of Morgan Stanley,  Dean Witter, Discover  &
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.
 
   
    InterCapital  and its wholly-owned subsidiary,  Dean Witter Services Company
Inc.,  serve  in  various   investment  management,  advisory,  management   and
administrative  capacities  to 100  investment  companies, thirty  of  which are
listed  on  the  New  York  Stock  Exchange,  with  combined  total  assets   of
approximately  $93.1  billion  at June  30,  1997. The  Investment  Manager also
manages portfolios of  pension plans, other  institutions and individuals  which
aggregated approximately $3.5 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. InterCapital  has  retained Dean  Witter  Services Company  Inc.  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, 1996, the Fund  accrued total compensation to the  Investment
Manager amounting to 0.42% of the Fund's average daily net assets and the Fund's
total expenses amounted to 1.25% of the Fund's average daily net assets.
 
INVESTMENT OBJECTIVE AND POLICIES
- --------------------------------------------------------------------------------
 
    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
 
                                       7
<PAGE>
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 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
 
                                       8
<PAGE>
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 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
 
                                       9
<PAGE>
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
 
                                       10
<PAGE>
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.
 
    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
 
                                       11
<PAGE>
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
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.
 
    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.
 
    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 InterCapital's Taxable Fixed-Income Group,  which
manages  twenty-four funds and fund portfolios, with approximately $12.8 billion
in assets  at  June  30,  1997.  Rajesh  K.  Gupta,  Senior  Vice  President  of
InterCapital and a member of InterCapital's Taxable Fixed-Income Group, has been
the primary portfolio manager of the Fund since July, 1992 and has been managing
    
 
                                       12
<PAGE>
portfolios  comprised  of government  securities at  InterCapital 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. ("DWR"), a
broker-dealer affiliate  of  InterCapital.  In  addition,  the  Fund  may  incur
brokerage  commissions on transactions  conducted through DWR  and other brokers
and dealers that are affiliates of InterCapital.
    
 
PURCHASE OF FUND SHARES
- --------------------------------------------------------------------------------
 
   
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 Dean
Witter  Distributors Inc.  (the "Distributor"),  an affiliate  of the Investment
Manager, shares of the  Fund are distributed by  the Distributor and offered  by
DWR  and other dealers  which have entered into  selected dealer agreements with
the Distributor ("Selected Broker-Dealers").  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; 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
employer-sponsored benefit 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,  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 or more and to
certain  other limited categories  of investors. For the  purpose of meeting the
minimum $5 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 Dean Witter Funds that
are multiple class funds  ("Dean Witter Multi-Class Funds")  and shares of  Dean
Witter  Funds sold  with a front-end  sales charge ("FSC  Funds") and concurrent
investments in Class  D shares  of the Fund  and other  Dean Witter  Multi-Class
Funds  will be aggregated. Subsequent  purchases of $100 or  more may be made by
sending a  check,  payable to  Dean  Witter U.S.  Government  Securities  Trust,
directly  to Dean Witter Trust Company (the  "Transfer Agent") at P.O. Box 1040,
Jersey City, NJ  07303 or by  contacting an  account executive of  DWR or  other
Selected Broker-Dealer.
    
 
                                       13
<PAGE>
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,  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. In  the  case of
investments pursuant to Systematic Payroll Deduction Plans (including Individual
Retirement Plans), the Fund, in  its discretion, may accept investments  without
regard to any minimum amounts which would otherwise be required, if the Fund 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 orders.
    
 
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 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.
 
                                       14
<PAGE>
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 employer-sponsored benefit  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 to a
 
                                       15
<PAGE>
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 minimum  investment amount for
Class D shares, holdings of Class A shares in all Dean Witter Multi-Class Funds,
shares of FSC Funds and shares of  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%      0.25%          No
           initial 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%     0.75%       B shares
           CDSC during the  (0.65% on   convert to A
           first year       amounts     shares
           decreasing to 0  over $10    automatically
           after six years  billion)    after
                                        approximately
                                        ten years
    C      1.0% CDSC          0.75%          No
           during first
           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 SINGLE         PUBLIC OFFERING    PERCENTAGE OF AMOUNT
       TRANSACTION                PRICE               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>
 
                                       16
<PAGE>
    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
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 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 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  Dean  Witter  Funds  previously
purchased at a price including a front-end sales charge (including shares of the
Fund  and other  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 equal  to at least  $5 million, 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 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 Dean Witter Funds acquired in exchange for shares
of such
    
 
                                       17
<PAGE>
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 Dean Witter Trust Company ("DWTC") or Dean Witter Trust
FSB ("DWTFSB")  (each  of which  is  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 or administrative services (such investments are subject
to all  of  the  terms  and  conditions of  such  programs,  which  may  include
termination fees and restrictions on transferability of Fund shares);
 
   (3)  retirement plans qualified under Section  401(k) of the Internal Revenue
Code ("401(k) plans") and other employer-sponsored plans qualified under Section
401(a) of the Internal Revenue Code with at least 200 eligible employees and for
which DWTC or DWTFSB serves as Trustee  or the 401(k) Support Services Group  of
DWR serves as recordkeeper;
 
   (4)  401(k) plans and other  employer-sponsored plans qualified under Section
401(a) of the Internal Revenue Code for  which DWTC or DWTFSB serves as  Trustee
or the 401(k) Support Services Group of DWR serves as recordkeeper 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 Dean Witter account executive who  joined
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 account executive'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.
 
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 employer-sponsored  benefit
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
 
                                       18
<PAGE>
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 OF
          PAYMENT MADE                 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 held by  401 (k) plans or  other
employer-sponsored  plans qualified under Section 401(a) of the Internal Revenue
Code for which DWTC or DWTFSB serves  as Trustee or the 401(k) Support  Services
Group  of DWR serves as  recordkeeper and whose accounts  are opened on or after
July 28, 1997, 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 OF
          PAYMENT MADE                 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  employer-sponsored benefit  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
employer-sponsored  benefit  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  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
401(k)  plan or other employer-sponsored plan  qualified under Section 401(a) of
the Internal  Revenue Code  which  offers investment  companies managed  by  the
Investment Manager or
 
                                       19
<PAGE>
its  subsidiary, Dean Witter Services  Company Inc., as self-directed investment
alternatives and  for which  DWTC or  DWTFSB  serves as  Trustee or  the  401(k)
Support Services Group of DWR serves as recordkeeper ("Eligible Plan"), provided
that  either:    (A)  the  plan  continues to  be  an  Eligible  Plan  after the
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 401(k)  plan  or other  employer-sponsored  plan
qualified  under Section 401(a) of the Internal  Revenue Code and for which DWTC
or DWTFSB serves as Trustee or the  401(k) Support Services Group of DWR  serves
as recordkeeper, 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
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 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
con-
 
                                       20
<PAGE>
version,  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.
 
    Class B shares purchased before  July 28, 1997 by  trusts for which DWTC  or
DWTFSB provides discretionary trustee services will convert to Class A shares on
or about August 29, 1997. The CDSC will not be applicable to such shares.
 
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 and the following
categories of investors: (i) investors participating in the InterCapital  mutual
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 or administrative services (subject to  all
of the terms and conditions of such programs, which may include termination fees
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 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 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 minimum investment  amount,
holdings  of Class A shares in all  Dean Witter Multi-Class Funds, shares of FSC
Funds and shares of 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
 
                                       21
<PAGE>
   
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 DWR's account executives
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, 1996,  Class B shares  of the Fund
accrued payments under the Plan amounting to $53,189,389, which amount is  equal
to  0.75%  of the  Fund's  average daily  net assets  for  the fiscal  year. The
payments accrued under the  Plan were calculated pursuant  to clause (b) of  the
compensation  formula under  the Plan.  All shares 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.
 
   
    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
$68,120,003 at December 31, 1996, which was equal to 1.06% of the net assets  of
the  Fund 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
    
 
                                       22
<PAGE>
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 account executives at the time of sale may be
reimbursed  in  the subsequent  calendar year.  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 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
    
gen-
 
                                       23
<PAGE>
erally  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.
 
   
    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  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  DWR  or  other  Selected  Broker-Dealer
account executive 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 adviser.
 
    For further information  regarding plan administration,  custodial fees  and
other  details, investors should contact their account executive or the Transfer
Agent.
 
EXCHANGE PRIVILEGE
 
    Shares of each Class may  be exchanged for shares of  the same Class of  any
other  Dean Witter Multi-Class Fund without  the imposition of any exchange fee.
Shares may also  be exchanged  for shares of  the following  funds: Dean  Witter
Short-Term  U.S. Treasury Trust, Dean Witter  Limited Term Municipal Trust, Dean
Witter Short-Term Bond Fund, Dean  Witter Intermediate Term U.S. Treasury  Trust
and  five Dean Witter funds which are money market funds (the "Exchange Funds").
Class A  shares may  also be  exchanged for  shares of  Dean Witter  Multi-State
Municipal  Series Trust and  Dean Witter Hawaii Municipal  Trust, which are Dean
Witter Funds sold with  a front-end sales charge  ("FSC Funds"). Class B  shares
may  also be exchanged for  shares of Dean Witter  Global Short-Term Income Fund
Inc., Dean  Witter High  Income Securities  and Dean  Witter National  Municipal
Trust, which are Dean
 
                                       24
<PAGE>
Witter Funds offered with a CDSC ("CDSC Funds"). 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 Dean Witter Multi-Class Fund, any FSC Fund, any CDSC
Fund 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 Dean Witter
Multi-Class Funds, FSC Funds or  CDSC Funds 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  Dean Witter Multi-Class
Fund or shares of  a CDSC Fund,  the holding period  previously frozen when  the
first  exchange was made resumes on the last day of the month in which shares of
a Dean Witter Multi-Class Fund  or shares of a  CDSC fund are reacquired.  Thus,
the  CDSC is based upon the time (calculated as described above) the shareholder
was invested in shares of a Dean Witter Multi-Class Fund or in shares of a  CDSC
fund (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. However, 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 Class  B shares  of another  Dean
Witter  Multi-Class  Fund or  shares  of a  CDSC  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 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 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
 
                                       25
<PAGE>
account executive  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 Dean Witter
Funds (for which the Exchange Privilege is available) pursuant to this  Exchange
Privilege   by  contacting  their  account   executive  (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 DWR  or other  Selected
Broker-Dealer  account  executive, 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 Dean Witter
Funds in the past.
 
    Shareholders should  contact  their  DWR  or  other  Selected  Broker-Dealer
account  executive  or  the Transfer  Agent  for further  information  about the
Exchange Privilege.
 
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,
 
                                       26
<PAGE>
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 by the Fund, the Distributor,
DWR  or  other Selected  Broker-Dealers.  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 account executive 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
 
                                       27
<PAGE>
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 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.
    
 
    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.
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 adviser.
 
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
 
                                       28
<PAGE>
   
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.
    
 
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 InterCapital,  Dean
Witter Services Company Inc. and the Distributor 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
 
                                       29
<PAGE>
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 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 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.
 
                                       30
<PAGE>
                        THE DEAN WITTER FAMILY OF FUNDS
 
<TABLE>
<S>                                                 <C>
MONEY MARKET FUNDS                                  FIXED-INCOME FUNDS
Dean Witter Liquid Asset Fund Inc.                  Dean Witter High Yield Securities Inc.
Dean Witter Tax-Free Daily Income Trust             Dean Witter Tax-Exempt Securities Trust
Dean Witter New York Municipal Money Market Trust   Dean Witter U.S. Government Securities Trust
Dean Witter California Tax-Free Daily Income Trust  Dean Witter California Tax-Free Income Fund
Dean Witter U.S. Government Money Market Trust      Dean Witter New York Tax-Free Income Fund
EQUITY FUNDS                                        Dean Witter Convertible Securities Trust
Dean Witter American Value Fund                     Dean Witter Federal Securities Trust
Dean Witter Natural Resource Development            Dean Witter World Wide Income Trust
 Securities Inc.                                    Dean Witter Intermediate Income Securities
Dean Witter Dividend Growth Securities Inc.         Dean Witter Global Short-Term Income Fund Inc.
Dean Witter Developing Growth Securities Trust      Dean Witter Multi-State Municipal Series Trust
Dean Witter World Wide Investment Trust             Dean Witter Short-Term U.S. Treasury Trust
Dean Witter Value-Added Market Series               Dean Witter Diversified Income Trust
Dean Witter Utilities Fund                          Dean Witter Limited Term Municipal Trust
Dean Witter Precious Metals and Minerals Trust      Dean Witter Short-Term Bond Fund
Dean Witter Capital Growth Securities               Dean Witter High Income Securities
Dean Witter European Growth Fund Inc.               Dean Witter National Municipal Trust
Dean Witter Pacific Growth Fund Inc.                Dean Witter Balanced Income Fund
Dean Witter Health Sciences Trust                   Dean Witter Hawaii Municipal Trust
Dean Witter Global Dividend Growth Securities       Dean Witter Intermediate Term U.S. Treasury
Dean Witter Global Utilities Fund                   Trust
Dean Witter International SmallCap Fund             DEAN WITTER RETIREMENT SERIES
Dean Witter Mid-Cap Growth Fund                     Liquid Asset Series
Dean Witter Balanced Growth Fund                    U.S. Government Money Market Series
Dean Witter Capital Appreciation Fund               U.S. Government Securities Series
Dean Witter Information Fund                        Intermediate Income Securities Series
Dean Witter Special Value Fund                      American Value Series
Dean Witter Financial Services Trust                Capital Growth Series
Dean Witter Market Leader Trust                     Dividend Growth Series
ASSET ALLOCATION FUNDS                              Strategist Series
Dean Witter Strategist Fund                         Utilities Series
Dean Witter Global Asset Allocation Fund            Value-Added Market Series
ACTIVE ASSETS ACCOUNT PROGRAM                       Global Equity Series
Active Assets Money Trust
Active Assets Tax-Free Trust
Active Assets Government Securities Trust
Active Assets California Tax-Free Trust
</TABLE>
 
<PAGE>
 
   
Dean Witter
U.S. Government Securities Trust
                                    Dean Witter
Two World Trade Center
New York, New York 10048
TRUSTEES                            U.S. Government
Michael Bozic                       Securities
Charles A. Fiumefreddo              Trust
Edwin J. Garn
John R. Haire
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
Dean Witter Trust Company
Harborside Financial Center
Plaza Two
Jersey City, New Jersey 07311
INDEPENDENT ACCOUNTANTS
Price Waterhouse LLP
1177 Avenue of the Americas
New York, New York 10036
INVESTMENT MANAGER
Dean Witter InterCapital Inc.
                                            PROSPECTUS -- JULY 28, 1997
 
    
<PAGE>
STATEMENT OF ADDITIONAL INFORMATION
 
<TABLE>
<S>                                                                <C>
JULY 28, 1997                                                         DEAN WITTER
                                                                    U.S. GOVERNMENT
                                                                    SECURITIES TRUST
</TABLE>
 
- --------------------------------------------------------------------------------
 
    Dean  Witter U.S.  Government Securities Trust  (the "Fund")  is an open-end
diversified management  investment  company  whose investment  objective  is  to
provide  high  current  income consistent  with  safety of  principal.  The Fund
invests only in 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 Government.
 
    A Prospectus for  the Fund  dated July 28,  1997, which  provides the  basic
information  you  should know  before  investing in  the  Fund, may  be obtained
without charge from the Fund at its address or telephone numbers listed below or
from the Fund's Distributor, Dean Witter Distributors Inc., or from Dean  Witter
Reynolds  Inc.  at  any of  its  branch  offices. This  Statement  of Additional
Information is not a prospectus. It contains information in addition to and more
detailed than that set forth  in the Prospectus. It  is intended to provide  you
additional  information regarding the activities and operations of the Fund, and
should be read in conjunction with the Prospectus.
 
Dean Witter
U.S. Government Securities Trust
Two World Trade Center
New York, New York 10048
(212) 392-2550 or (800) 869-NEWS
<PAGE>
TABLE OF CONTENTS
- --------------------------------------------------------------------------------
 
   
<TABLE>
<S>                                                                                      <C>
The Fund and its Management............................................................          3
 
Trustees and Officers..................................................................          7
 
Investment Practices and Policies......................................................         13
 
Investment Restrictions................................................................         14
 
Portfolio Transactions and Brokerage...................................................         14
 
The Distributor........................................................................         16
 
Determination of Net Asset Value.......................................................         20
 
Purchase of Fund Shares................................................................         20
 
Shareholder Services...................................................................         23
 
Redemptions and Repurchases............................................................         27
 
Dividends, Distributions and Taxes.....................................................         29
 
Performance Information................................................................         30
 
Description of Shares of the Fund......................................................         31
 
Custodian and Transfer Agent...........................................................         32
 
Independent Accountants................................................................         32
 
Reports to Shareholders................................................................         32
 
Legal Counsel..........................................................................         32
 
Experts................................................................................         32
 
Registration Statement.................................................................         32
 
Report of Independent Accountants......................................................         33
 
Financial Statements -- December 31, 1996..............................................         34
</TABLE>
    
 
                                       2
<PAGE>
THE FUND AND ITS MANAGEMENT
- --------------------------------------------------------------------------------
 
THE FUND
 
    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.
 
THE INVESTMENT MANAGER
 
    Dean  Witter InterCapital Inc. (the "Investment Manager" or "InterCapital"),
a Delaware corporation, whose address is  Two World Trade Center, New York,  New
York  10048, is  the Fund's Investment  Manager. InterCapital  is a wholly-owned
subsidiary of Morgan Stanley, Dean Witter, Discover & Co. ("MSDWD"), a  Delaware
corporation.  In an internal  reorganization which took  place in January, 1993,
InterCapital assumed  the  investment advisory,  administrative  and  management
activities  previously  performed by  the InterCapital  Division of  Dean Witter
Reynolds  Inc.  ("DWR"),   a  broker-dealer  affiliate   of  InterCapital.   (As
hereinafter  used  in  this  Statement  of  Additional  Information,  the  terms
"InterCapital" and  "Investment Manager"  refer to  DWR's InterCapital  Division
prior   to  the  internal  reorganization  and  Dean  Witter  InterCapital  Inc.
thereafter.) The  daily management  of the  Fund and  research relating  to  the
Fund's portfolio are conducted by or under the direction of officers of the Fund
and of the Investment Manager, subject to periodic review by the Fund's Board of
Trustees.  Information as to these Trustees  and officers is contained under the
caption "Trustees and Officers."
 
    The Investment Manager is  the investment manager  or investment adviser  of
the following investment companies:
 
OPEN-END FUNDS
 
<TABLE>
<C>        <S>
       1.  Active Assets California Tax-Free Trust
       2.  Active Assets Government Securities
            Trust
       3.  Active Assets Money Trust
       4.  Active Assets Tax-Free Trust
       5.  Dean Witter American Value Fund
       6.  Dean Witter Balanced Growth Fund
       7.  Dean Witter Balanced Income Fund
       8.  Dean Witter California Tax-Free Daily
            Income Trust
       9.  Dean Witter California Tax-Free Income
            Fund
      10.  Dean Witter Capital Appreciation Fund
      11.  Dean Witter Capital Growth Securities
      12.  Dean Witter Convertible Securities Trust
      13.  Dean Witter Developing Growth Securities
            Trust
      14.  Dean Witter Diversified Income Trust
      15.  Dean Witter Dividend Growth Securities
            Inc.
      16.  Dean Witter European Growth Fund Inc.
      17.  Dean Witter Federal Securities Trust
      18.  Dean Witter Financial Services Trust
      19.  Dean Witter Global Asset Allocation Fund
      20.  Dean Witter Global Dividend Growth
            Securities
      21.  Dean Witter Global Short-Term Income
            Fund Inc.
      22.  Dean Witter Global Utilities Fund
      23.  Dean Witter Hawaii Municipal Trust
      24.  Dean Witter Health Sciences Trust
      25.  Dean Witter High Income Securities
      26.  Dean Witter High Yield Securities Inc.
      27.  Dean Witter Income Builder Fund
      28.  Dean Witter Information Fund
      29.  Dean Witter Intermediate Income
            Securities
      30.  Dean Witter Intermediate Term U.S.
            Treasury Trust
      31.  Dean Witter International SmallCap Fund
      32.  Dean Witter Japan Fund
      33.  Dean Witter Limited Term Municipal Trust
      34.  Dean Witter Liquid Asset Fund Inc.
      35.  Dean Witter Market Leader Trust
      36.  Dean Witter Mid-Cap Growth Fund
      37.  Dean Witter Multi-State Municipal Series
            Trust
      38.  Dean Witter National Municipal Trust
      39.  Dean Witter Natural Resource Development
            Securities Inc.
      40.  Dean Witter New York Municipal Money
            Market Trust
      41.  Dean Witter New York Tax-Free Income
            Fund
      42.  Dean Witter Pacific Growth Fund Inc.
      43.  Dean Witter Precious Metals and Minerals
            Trust
      44.  Dean Witter Retirement Series
</TABLE>
 
                                       3
<PAGE>
<TABLE>
<C>        <S>
      45.  Dean Witter Select Dimensions Investment
            Series
      46.  Dean Witter Select Municipal
            Reinvestment Fund
      47.  Dean Witter Short-Term Bond Fund
      48.  Dean Witter Short-Term U.S. Treasury
            Trust
      49.  Dean Witter Special Value Fund
      50.  Dean Witter Strategist Fund
      51.  Dean Witter Tax-Exempt Securities Trust
      52.  Dean Witter Tax-Free Daily Income Trust
      53.  Dean Witter U.S. Government Money Market
            Trust
      54.  Dean Witter U.S. Government Securities
            Trust
      55.  Dean Witter Utilities Fund
      56.  Dean Witter Value-Added Market Series
      57.  Dean Witter Variable Investment Series
      58.  Dean Witter World Wide Income Trust
      59.  Dean Witter World Wide Investment Trust
</TABLE>
 
CLOSED-END FUNDS
 
<TABLE>
<C>        <S>
       1.  High Income Advantage Trust
       2.  High Income Advantage Trust II
       3.  High Income Advantage Trust III
       4.  InterCapital Income Securities Inc.
       5.  Dean Witter Government Income Trust
       6.  InterCapital Insured Municipal Bond
            Trust
       7.  InterCapital Insured Municipal Trust
       8.  InterCapital Insured Municipal Income
            Trust
       9.  InterCapital California Insured
            Municipal Income Trust
      10.  InterCapital Insured Municipal
            Securities
      11.  InterCapital Insured California
            Municipal Securities
      12.  InterCapital Quality Municipal
            Investment Trust
      13.  InterCapital Quality Municipal Income
            Trust
      14.  InterCapital Quality Municipal
            Securities
      15.  InterCapital California Quality
            Municipal Securities
      16.  InterCapital New York Quality Municipal
            Securities
      17.  Municipal Income Trust
      18.  Municipal Income Trust II
      19.  Municipal Income Trust III
      20.  Municipal Income Opportunities Trust
      21.  Municipal Income Opportunities II
      22.  Municipal Income Opportunities III
      23.  Prime Income Trust
      24.  Municipal Premium Income Trust
</TABLE>
 
    The foregoing investment companies, together with the Fund, are collectively
referred to as the Dean Witter Funds.
 
    In  addition,  Dean Witter  Services Company  Inc. ("DWSC"),  a wholly-owned
subsidiary of InterCapital, serves  as manager for  the following companies  for
which TCW Funds Management, Inc. is the investment adviser (the "TCW/DW Funds"):
 
<TABLE>
<C>        <S>
OPEN-END FUNDS
       1.  TCW/DW Core Equity Trust
       2.  TCW/DW North American Government Income
            Trust
       3.  TCW/DW Latin American Growth Fund
       4.  TCW/DW Income and Growth Fund
       5.  TCW/DW Small Cap Growth Fund
       6.  TCW/DW Balanced Fund
       7.  TCW/DW Mid-Cap Equity Trust
       8.  TCW/DW Global Telecom Trust
       9.  TCW/DW Strategic Income Trust
 
CLOSED-END FUNDS
      10.  TCW/DW Term Trust 2000
      11.  TCW/DW Term Trust 2002
      12.  TCW/DW Term Trust 2003
      13.  TCW/DW Total Return Trust
      14.  TCW/DW Emerging Markets Opportunities
            Trust
</TABLE>
 
   
    InterCapital  also serves as:  (i) administrator of  The BlackRock Strategic
Term Trust Inc., a closed-end investment company; and (ii) sub-administrator  of
MassMutual  Participation  Investors  and  Templeton  Global  Governments Income
Trust, closed-end investment companies.
    
 
    Pursuant to an  Investment Management Agreement  (the "Agreement") with  the
Investment  Manager, the Fund has retained  the Investment Manager to manage the
investment of  the  Fund's assets,  including  the  placing of  orders  for  the
purchase   and   sale   of   portfolio   securities.   The   Investment  Manager
 
                                       4
<PAGE>
obtains and  evaluates such  information  and advice  relating to  the  economy,
securities  markets, and specific securities as it considers necessary or useful
to continuously manage the assets  of the Fund in  a manner consistent with  its
investment objective and policies.
 
    Under  the  terms  of the  Agreement,  in  addition to  managing  the Fund's
investments, the Investment Manager  maintains certain of  the Fund's books  and
records  and  furnishes,  at its  own  expense, such  office  space, facilities,
equipment, clerical help, bookkeeping and certain legal services as the Fund may
reasonably require in the conduct of its business, including the preparation  of
prospectuses, proxy statements and reports required to be filed with federal and
state  securities commissions (except insofar as the participation or assistance
of independent accountants and  attorneys is, in the  opinion of the  Investment
Manager,  necessary or desirable). In addition,  the Investment Manager pays the
salaries of all personnel, including officers of the Fund, who are employees  of
the  Investment Manager. The Investment Manager also bears the cost of telephone
service, heat, light, power and other utilities provided to the Fund.
 
    Effective December  31,  1993,  pursuant to  a  Services  Agreement  between
InterCapital  and DWSC, DWSC began to provide the administrative services to the
Fund which  were previously  performed directly  by InterCapital.  On April  17,
1995,  DWSC was  reorganized in the  State of Delaware,  necessitating the entry
into a  new  Services Agreement  by  InterCapital and  DWSC  on that  date.  The
foregoing internal reorganizations did not result in any change in the nature or
scope  of the administrative services  being provided to the  Fund or any of the
fees being paid by the Fund for  the overall services being performed under  the
terms of the existing Management Agreement.
 
    Expenses not expressly assumed by the Investment Manager under the Agreement
or  by  the Distributor  of  the Fund's  shares,  Dean Witter  Distributors Inc.
("Distributors" or the "Distributor") (see  "The Distributor"), will be paid  by
the  Fund. These expenses will be allocated  among the four classes of shares of
the Fund  (each, a  "Class")  pro rata  based  on the  net  assets of  the  Fund
attributable to each Class, except as described below. The expenses borne by the
Fund  include, but  are not  limited to:  expenses of  the Plan  of Distribution
pursuant to Rule 12b-1  (the "12b-1 fee") (see  "The Distributor"); charges  and
expenses  of any  registrar, custodian,  stock transfer  and dividend disbursing
agent; brokerage commissions; taxes; engraving and printing share  certificates;
registration costs of the Fund and its shares under federal and state securities
laws;  the cost and expense of printing, including typesetting, and distributing
prospectuses  and  statements  of  additional   information  of  the  Fund   and
supplements  thereto to the  Fund's shareholders; all  expenses of shareholders'
and  Trustees'  meetings  and  of  preparing,  printing  and  mailing  of  proxy
statements  and reports to shareholders; fees and travel expenses of Trustees or
members of  any  advisory  board or  committee  who  are not  employees  of  the
Investment  Manager or  any corporate affiliate  of the  Investment Manager; all
expenses incident to any dividend, withdrawal or redemption options; charges and
expenses of any outside service used for pricing of the Fund's shares; fees  and
expenses  of  legal  counsel, including  counsel  to  the Trustees  who  are not
interested persons  of the  Fund or  of the  Investment Manager  (not  including
compensation  or  expenses  of attorneys  who  are employees  of  the Investment
Manager) and independent accountants; membership dues of industry  associations;
interest  on  Fund  borrowings;  postage;  insurance  premiums  on  property  or
personnel (including  officers and  Trustees) of  the Fund  which inure  to  its
benefit; extraordinary expenses (including, but not limited to, legal claims and
liabilities  and litigation costs and any indemnification relating thereto); and
all other costs of the Fund's operation. The 12b-1 fees relating to a particular
Class will be  allocated directly  to that  Class. In  addition, other  expenses
associated  with a particular  Class (except advisory or  custodial fees) may be
allocated directly to  that Class,  provided that such  expenses are  reasonably
identified  as specifically attributable to that Class and the direct allocation
to that Class is approved by the Trustees.
 
    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  by  applying  the
following annual rates to the Fund's daily net assets pursuant to the Agreement:
0.50%  of the portion of such daily  net assets not exceeding $1 billion; 0.475%
of the portion of such daily net  assets exceeding $1 billion but not  exceeding
$1.5 billion; 0.45% of the portion of such
 
                                       5
<PAGE>
daily  net assets exceeding $1.5 billion but not exceeding $2 billion; 0.425% of
the portion of such daily net assets exceeding $2 billion but not exceeding $2.5
billion; 0.40% of that portion of  such daily net assets exceeding $2.5  billion
but  not exceeding $5 billion;  0.375% of that portion  of such daily net assets
exceeding $5 billion but  not exceeding $7.5 billion;  0.35% of that portion  of
such  daily net  assets exceeding  $7.5 billion  but not  exceeding $10 billion;
0.325% of that portion of  such daily net assets  exceeding $10 billion but  not
exceeding  $12.5 billion;  and 0.30%  of that portion  of such  daily net assets
exceeding $12.5 billion. For the fiscal years ended December 31, 1994, 1995  and
1996,  the  Fund  accrued  to  the  Investment  Manager  total  compensation  of
$40,553,081, $33,295,918 and $29,579,546, respectively.
 
    The Agreement  provides that  in  the absence  of willful  misfeasance,  bad
faith, gross negligence or reckless disregard of its obligations thereunder, the
Investment Manager is not liable to the Fund or any of its investors for any act
or omission by the Investment Manager or for any losses sustained by the Fund or
its  investors.  The Agreement  does not  restrict  the Investment  Manager from
acting as investment manager or adviser to others.
 
    The Agreement was initially  approved by the Trustees  on February 21,  1997
and by the shareholders of the Fund at a Special Meeting of Shareholders held on
May  21, 1997.  The Agreement is  substantially identical to  a prior investment
management agreement which was initially approved by the Trustees on October 30,
1992 and by the shareholders  of the Fund at  a Special Meeting of  Shareholders
held  on January 12,  1993. The Agreement took  effect on May  31, 1997 upon the
consummation of the merger  of Dean Witter, Discover  & Co. with Morgan  Stanley
Group  Inc. The  Agreement may  be terminated at  any time,  without penalty, on
thirty days' notice by the  Board of Trustees of the  Fund, by the holders of  a
majority,  as defined in the Investment Company  Act of 1940 (the "Act"), of the
outstanding shares of the Fund, or by the Investment Manager. The Agreement will
automatically terminate in the event of its assignment (as defined in the Act).
 
    Under its terms, the Agreement has an initial term ending April 30, 1999 and
will remain in effect from year to year thereafter, provided continuance of  the
Agreement is approved at least annually by the vote of the holders of a majority
(as  defined in the Act) of the outstanding  shares of the Fund, or by the Board
of Trustees  of the  Fund; provided  that in  either event  such continuance  is
approved  annually by the vote of a majority of the Trustees of the Fund who are
not parties to the Agreement or "interested persons" (as defined in the Act)  of
any  such party (the "Independent Trustees"), which  vote must be cast in person
at a meeting called for the purpose of voting on such approval.
 
    The Fund has acknowledged that the name "Dean Witter" is a property right of
DWR. The Fund has agreed that DWR or its parent company may use or, at any time,
permit others to use, the name "Dean  Witter." The Fund has also agreed that  in
the   event  the  Agreement  is  terminated,   or  if  the  affiliation  between
InterCapital and its parent company is  terminated, the Fund will eliminate  the
name "Dean Witter" from its name if DWR or its parent company shall so request.
 
                                       6
<PAGE>
TRUSTEES AND OFFICERS
- --------------------------------------------------------------------------------
 
    The  Trustees and Executive  Officers of the  Fund, their principal business
occupations during the  last five  years and  their affiliations,  if any,  with
InterCapital and with the 83 Dean Witter Funds and the 14 TCW/DW Funds are shown
below.
 
   
<TABLE>
<CAPTION>
   NAME, AGE, POSITION WITH FUND AND
                ADDRESS                                PRINCIPAL OCCUPATIONS DURING LAST FIVE YEARS
- ----------------------------------------  ----------------------------------------------------------------------
<S>                                       <C>
Michael Bozic (56)                        Chairman  and Chief Executive Officer  of Levitz Furniture Corporation
Trustee                                   (since November, 1995); Director or Trustee of the Dean Witter  Funds;
c/o Levitz Furniture Corporation          formerly  President and  Chief Executive  Officer of  Hills Department
6111 Broken Sound Parkway, N.W.           Stores (May,  1991-July,  1995); formerly  variously  Chairman,  Chief
Boca Raton, Florida                       Executive   Officer,  and   President  and   Chief  Operating  Officer
                                          (1987-1991) of the Sears Merchandise Group of Sears, Roebuck and  Co.;
                                          Director  of  Eaglemark  Financial Services,  Inc.,  the  United Negro
                                          College Fund and Weirton Steel Corporation.
 
Charles A. Fiumefreddo* (64)              Chairman, Chief Executive Officer  and Director of InterCapital,  DWSC
Chairman of the Board, President,         and  Distributors;  Executive  Vice  President  and  Director  of DWR;
Chief Executive Officer and Trustee       Chairman, Director or Trustee,  President and Chief Executive  Officer
Two World Trade Center                    of  the  Dean  Witter  Funds; Chairman,  Chief  Executive  Officer and
New York, New York                        Trustee of  the TCW/DW  Funds; Chairman  and Director  of Dean  Witter
                                          Trust  Company  ("DWTC");  Director and/or  officer  of  various MSDWD
                                          subsidiaries; formerly Executive Vice  President and Director of  Dean
                                          Witter, Discover & Co. (until February, 1993).
 
Edwin J. Garn (64)                        Director  or Trustee of the Dean  Witter Funds; formerly United States
Trustee                                   Senator (R-Utah) (1974-1992)  and Chairman,  Senate Banking  Committee
c/o Huntsman Corporation                  (1980-1986);  formerly  Mayor  of Salt  Lake  City,  Utah (1971-1974);
500 Huntsman Way                          formerly Astronaut, Space Shuttle Discovery (April 12-19, 1985);  Vice
Salt Lake City, Utah                      Chairman,  Huntsman  Corporation  (since January,  1993);  Director of
                                          Franklin Quest  (time management  systems)  and John  Alden  Financial
                                          Corp.  (health insurance);  member of the  board of  various civic and
                                          charitable organizations.
 
John R. Haire (72)                        Chairman of the Audit Committee and  Chairman of the Committee of  the
Trustee                                   Independent  Directors or Trustees and Director or Trustee of the Dean
Two World Trade Center                    Witter Funds;  Chairman of  the Audit  Committee and  Chairman of  the
New York, New York                        Committee of the Independent Trustees and Trustee of the TCW/DW Funds;
                                          formerly  President,  Council  for Aid  to  Education  (1978-1989) and
                                          Chairman  and  Chief  Executive  Officer  of  Anchor  Corporation,  an
                                          Investment   Adviser  (1964-1978);  Director  of  Washington  National
                                          Corporation (insurance).
</TABLE>
    
 
                                       7
<PAGE>
   
<TABLE>
<CAPTION>
   NAME, AGE, POSITION WITH FUND AND
                ADDRESS                                PRINCIPAL OCCUPATIONS DURING LAST FIVE YEARS
- ----------------------------------------  ----------------------------------------------------------------------
<S>                                       <C>
Wayne E. Hedien** (63)                    Retired; Director or Trustee of  the Dean Witter Funds (commencing  on
Trustee                                   September  1, 1997); Director of The PMI Group, Inc. (private mortgage
c/o Gordon Altman Butowsky                insurance); Trustee and Vice Chairman  of The Field Museum of  Natural
 Weitzen Shalov & Wein                    History;  formerly associated with the Allstate Companies (1966-1994),
Counsel to the Independent Trustees       most  recently  as  Chairman  of  The  Allstate  Corporation   (March,
114 West 47th Street                      1993-December,  1994) and Chairman and  Chief Executive Officer of its
New York, New York                        wholly-owned   subsidiary,   Allstate    Insurance   Company    (July,
                                          1989-December,   1994);  director   of  various   other  business  and
                                          charitable organizations.
 
Dr. Manuel H. Johnson (48)                Senior Partner, Johnson Smick International, Inc., a consulting  firm;
Trustee                                   Co-Chairman  and a  founder of  the Group  of Seven  Council (G7C), an
c/o Johnson Smick International, Inc.     international economic  commission; Director  or Trustee  of the  Dean
1133 Connecticut Avenue, N.W.             Witter  Funds; Trustee of the TCW/DW  Funds; Director of NASDAQ (since
Washington, DC                            June,   1995);   Director   of   Greenwich   Capital   Markets,   Inc.
                                          (broker-dealer);   Trustee  of  the  Financial  Accounting  Foundation
                                          (oversight organization of the Financial Accounting Standards  Board);
                                          formerly  Vice  Chairman  of the  Board  of Governors  of  the Federal
                                          Reserve  System  (1986-1990)  and  Assistant  Secretary  of  the  U.S.
                                          Treasury (1982-1986).
 
Michael E. Nugent (61)                    General   Partner,   Triumph  Capital,   LP.,  a   private  investment
Trustee                                   partnership; Director or Trustee of the Dean Witter Funds; Trustee  of
c/o Triumph Capital, L.P.                 the  TCW/DW Funds; formerly Vice  President, Bankers Trust Company and
237 Park Avenue                           BT Capital  Corporation  (1984-1988);  Director  of  various  business
New York, New York                        organizations.
 
Philip J. Purcell* (53)                   Chairman  of the  Board of  Directors and  Chief Executive  Officer of
Trustee                                   MSDWD, DWR and Novus Credit  Services Inc.; Director of  InterCapital,
1585 Broadway                             DWSC  and Distributors; Director or Trustee  of the Dean Witter Funds;
New York, New York                        Director and/or officer of various MSDWD subsidiaries.
 
John L. Schroeder (66)                    Retired; Director or Trustee of the Dean Witter Funds; Trustee of  the
Trustee                                   TCW/DW   Funds;  Director  of  Citizens  Utilities  Company;  formerly
c/o Gordon Altman Butowsky                Executive Vice  President and  Chief Investment  Officer of  the  Home
 Weitzen Shalov & Wein                    Insurance Company (August, 1991-September, 1995).
Counsel to the Independent Trustees
114 West 47th Street
New York, New York
</TABLE>
    
 
                                       8
<PAGE>
<TABLE>
<CAPTION>
   NAME, AGE, POSITION WITH FUND AND
                ADDRESS                                PRINCIPAL OCCUPATIONS DURING LAST FIVE YEARS
- ----------------------------------------  ----------------------------------------------------------------------
<S>                                       <C>
Barry Fink (42)                           Senior  Vice President (since  March, 1997) and  Secretary and General
Vice President, Secretary                 Counsel (since February, 1997) of  InterCapital and DWSC; Senior  Vice
  and General Counsel                     President  (since March,  1997) and Assistant  Secretary and Assistant
Two World Trade Center                    General Counsel  (since  February, 1997)  of  Distributors;  Assistant
New York, New York                        Secretary  of DWR (since August,  1996); Vice President, Secretary and
                                          General Counsel of the Dean Witter Funds and the TCW/ DW Funds  (since
                                          February, 1997); previously First Vice President (June, 1993-February,
                                          1997),  Vice President (until June,  1993) and Assistant Secretary and
                                          Assistant General  Counsel  of  InterCapital and  DWSC  and  Assistant
                                          Secretary of the Dean Witter Funds and the TCW/DW Funds.
 
Rajesh K. Gupta (37)                      Senior  Vice President of InterCapital; Vice President of various Dean
Vice President                            Witter Funds.
Two World Trade Center
New York, New York
 
Thomas F. Caloia (51)                     First Vice President and Assistant Treasurer of InterCapital and DWSC;
Treasurer                                 Treasurer of the Dean Witter Funds and the TCW/DW Funds.
Two World Trade Center
New York, New York
</TABLE>
 
- ------------
 *Denotes Trustees who are "interested persons"  of the Fund, as defined in  the
  Act.
**Mr. Hedien's term as Trustee will commence on September 1, 1997.
 
   
    In  addition, Robert  M. Scanlan, President  and Chief  Operating Officer of
InterCapital and DWSC,  Executive Vice  President of Distributors  and DWTC  and
Director  of DWTC, Mitchell  M. Merin, President and  Chief Strategic Officer of
InterCapital and DWSC,  Executive Vice  President of Distributors  and DWTC  and
Director  of DWTC, Executive Vice President and Director of DWR, and Director of
SPS Transaction Services, Inc. and  various other MSDWD subsidiaries, Joseph  J.
McAlinden, Executive Vice President and Chief Investment Officer of InterCapital
and   Director  of  DWTC,   Robert  S.  Giambrone,   Senior  Vice  President  of
InterCapital, DWSC, Distributors  and DWTC and  Director of DWTC,  and Peter  M.
Avelar,  Jonathan  R. Page  and  James F.  Willison,  Senior Vice  Presidents of
InterCapital, are Vice  Presidents of the  Fund, and Marilyn  K. Cranney,  First
Vice  President and Assistant General Counsel of InterCapital and DWSC, Lou Anne
D. McInnis, Carsten Otto and Ruth  Rossi, Vice Presidents and Assistant  General
Counsels  of InterCapital and DWSC, and Frank Bruttomesso, a Staff Attorney with
InterCapital, are Assistant Secretaries of the Fund.
    
 
THE BOARD OF TRUSTEES, THE INDEPENDENT TRUSTEES, AND THE COMMITTEES
 
   
    The Board of  Trustees currently consists  of eight (8)  trustees; as  noted
above,  Mr.  Hedien's  term  will  commence on  September  1,  1997.  These same
individuals also  serve as  directors or  trustees for  all of  the Dean  Witter
Funds,  and are referred to in this section  as Trustees. As of the date of this
Statement of Additional Information, there are a total of 83 Dean Witter  Funds,
comprised  of 126  portfolios. As of  June 30,  1997, the Dean  Witter Funds had
total net  assets of  approximately  $87.9 billion  and  more than  six  million
shareholders.
    
 
    Six Trustees and Mr. Hedien (77% of the total number) have no affiliation or
business  connection with InterCapital  or any of its  affiliated persons and do
not own any stock or other  securities issued by InterCapital's parent  company,
MSDWD.  These are the  "disinterested" or "independent"  Trustees. The other two
Trustees (the "management Trustees") are  affiliated with InterCapital. Four  of
the six independent Trustees are also Independent Trustees of the TCW/DW Funds.
 
                                       9
<PAGE>
    Law and regulation establish both general guidelines and specific duties for
the  Independent Trustees.  The Dean Witter  Funds seek  as Independent Trustees
individuals of distinction  and experience in  business and finance,  government
service  or academia; these are people whose advice and counsel are in demand by
others and for  whom there is  often competition.  To accept a  position on  the
Funds'  Boards, such individuals may reject other attractive assignments because
the Funds make  substantial demands  on their time.  Indeed, by  serving on  the
Funds'  Boards, certain Trustees who would  otherwise be qualified and in demand
to serve on bank boards would be prohibited by law from doing so.
 
    All of  the current  Independent  Trustees serve  as  members of  the  Audit
Committee  and the  Committee of  the Independent  Trustees. Three  of them also
serve as members of  the Derivatives Committee. During  the calendar year  ended
December  31,  1996,  the three  Committees  held  a combined  total  of sixteen
meetings. The Committees hold some  meetings at InterCapital's offices and  some
outside  InterCapital.  Management  Trustees  or officers  do  not  attend these
meetings unless  they are  invited  for purposes  of furnishing  information  or
making a report.
 
    The  Committee of the  Independent Trustees is  charged with recommending to
the full Board  approval of management,  advisory and administration  contracts,
Rule  12b-1  plans  and distribution  and  underwriting  agreements; continually
reviewing Fund performance;  checking on  the pricing  of portfolio  securities,
brokerage  commissions, transfer agent costs  and performance, and trading among
Funds in the  same complex; and  approving fidelity bond  and related  insurance
coverage and allocations, as well as other matters that arise from time to time.
The Independent Trustees are required to select and nominate individuals to fill
any  Independent Trustee vacancy on the Board of  any Fund that has a Rule 12b-1
plan of distribution. Most of the Dean Witter Funds have such a plan.
 
    The Audit  Committee is  charged with  recommending to  the full  Board  the
engagement  or  discharge  of  the  Fund's  independent  accountants;  directing
investigations into matters  within the  scope of  the independent  accountants'
duties,  including the power  to retain outside  specialists; reviewing with the
independent accountants the audit plan  and results of the auditing  engagement;
approving  professional  services provided  by  the independent  accountants and
other accounting firms prior to the performance of such services; reviewing  the
independence  of the independent accountants; considering the range of audit and
non-audit fees;  reviewing  the  adequacy  of  the  Fund's  system  of  internal
controls;  and preparing  and submitting Committee  meeting minutes  to the full
Board.
 
    Finally, the  Board of  each  Fund has  formed  a Derivatives  Committee  to
establish  parameters for and oversee the activities of the Fund with respect to
derivative investments, if any, made by the Fund.
 
DUTIES OF CHAIRMAN OF COMMITTEE OF THE INDEPENDENT TRUSTEES AND AUDIT COMMITTEE
 
    The Chairman of  the Committee  of the  Independent Trustees  and the  Audit
Committee  maintains an  office at  the Funds' headquarters  in New  York. He is
responsible for keeping abreast of regulatory and industry developments and  the
Funds'  operations and management. He  screens and/or prepares written materials
and identifies  critical  issues  for  the  Independent  Trustees  to  consider,
develops  agendas  for Committee  meetings, determines  the  type and  amount of
information that the Committees will need to form a judgment on various  issues,
and  arranges to have  that information furnished to  Committee members. He also
arranges for  the services  of independent  experts and  consults with  them  in
advance  of meetings  to help  refine reports and  to focus  on critical issues.
Members of the Committees believe that the person who serves as Chairman of both
Committees and guides their efforts is  pivotal to the effective functioning  of
the Committees.
 
    The  Chairman of the  Committees also maintains  continuous contact with the
Funds' management, with independent counsel to the Independent Trustees and with
the Funds' independent auditors.  He arranges for a  series of special  meetings
involving  the  annual  review  of  investment  advisory,  management  and other
operating contracts of  the Funds  and, on  behalf of  the Committees,  conducts
negotiations with the Investment Manager and other service providers. In effect,
the  Chairman of the Committees  serves as a combination  of chief executive and
support staff of the Independent Trustees.
 
                                       10
<PAGE>
    The Chairman of  the Committee  of the  Independent Trustees  and the  Audit
Committee  is  not  employed by  any  other  organization and  devotes  his time
primarily to  the services  he performs  as Committee  Chairman and  Independent
Trustee  of the Dean Witter Funds and  as an Independent Trustee and, since July
1, 1996, as Chairman of the Committee of the Independent Trustees and the  Audit
Committee  of the TCW/DW Funds. The current Committee Chairman has had more than
35 years experience as a senior executive in the investment company industry.
 
ADVANTAGES OF HAVING SAME INDIVIDUALS AS INDEPENDENT TRUSTEES FOR ALL DEAN
WITTER FUNDS
 
    The Independent Trustees and the  Funds' management believe that having  the
same  Independent  Trustees  for  each  of  the  Dean  Witter  Funds  avoids the
duplication  of  effort  that  would  arise  from  having  different  groups  of
individuals  serving as Independent  Trustees for each  of the Funds  or even of
sub-groups of Funds.  They believe  that having  the same  individuals serve  as
Independent  Trustees of  all the  Funds tends  to increase  their knowledge and
expertise regarding matters which affect the Fund complex generally and enhances
their ability  to negotiate  on behalf  of  each Fund  with the  Fund's  service
providers. This arrangement also precludes the possibility of separate groups of
Independent  Trustees arriving at conflicting decisions regarding operations and
management of the  Funds and  avoids the cost  and confusion  that would  likely
ensue.  Finally, having the  same Independent Trustees serve  on all Fund Boards
enhances the ability of  each Fund to  obtain, at modest  cost to each  separate
Fund,  the services of Independent Trustees, and a Chairman of their Committees,
of the caliber, experience and business  acumen of the individuals who serve  as
Independent Trustees of the Dean Witter Funds.
 
COMPENSATION OF INDEPENDENT TRUSTEES
 
    The  Fund pays each Independent  Trustee an annual fee  of $1,000 plus a per
meeting fee of $50 for  meetings of the Board of  Trustees or committees of  the
Board  of Trustees attended  by the Trustee  (the Fund pays  the Chairman of the
Audit Committee an annual fee of $750 and pays the Chairman of the Committee  of
the  Independent Trustees  an additional  annual fee  of $1,200).  The Fund also
reimburses such Trustees for travel and other out-of-pocket expenses incurred by
them in connection with  attending such meetings. Trustees  and officers of  the
Fund  who are or have  been employed by the  Investment Manager or an affiliated
company receive no compensation or expense reimbursement from the Fund.
 
    The  following  table  illustrates  the  compensation  paid  to  the  Fund's
Independent Trustees by the Fund for the fiscal year ended December 31, 1996.
 
                               FUND COMPENSATION
 
<TABLE>
<CAPTION>
                                                                   AGGREGATE
                                                                 COMPENSATION
NAME OF INDEPENDENT TRUSTEE                                      FROM THE FUND
- --------------------------------------------------------------  ---------------
<S>                                                             <C>
Michael Bozic.................................................      $1,800
Edwin J. Garn.................................................       1,850
John R. Haire.................................................       3,950
Dr. Manuel H. Johnson.........................................       1,800
Michael E. Nugent.............................................       1,800
John L. Schroeder.............................................       1,800
</TABLE>
 
    The  following  table  illustrates  the  compensation  paid  to  the  Fund's
Independent Trustees for the calendar year ended December 31, 1996 for  services
to  the 82 Dean Witter Funds and, in  the case of Messrs. Haire, Johnson, Nugent
and Schroeder, the 14 TCW/DW Funds that were in operation at December 31,  1996.
With  respect  to  Messrs.  Haire, Johnson,  Nugent  and  Schroeder,  the TCW/DW
 
                                       11
<PAGE>
Funds are included solely because of a limited exchange privilege between  those
Funds and five Dean Witter Money Market Funds.
 
           CASH COMPENSATION FROM DEAN WITTER FUNDS AND TCW/DW FUNDS
 
<TABLE>
<CAPTION>
                                                                   FOR SERVICE AS    FOR SERVICE
                                                                    CHAIRMAN OF          AS          TOTAL CASH
                                                                   COMMITTEES OF     CHAIRMAN OF    COMPENSATION
                               FOR SERVICE                          INDEPENDENT     COMMITTEES OF   FOR SERVICES
                              AS DIRECTOR OR                         DIRECTORS/      INDEPENDENT         TO
                               TRUSTEE AND       FOR SERVICE AS     TRUSTEES AND    TRUSTEES AND       82 DEAN
                             COMMITTEE MEMBER     TRUSTEE AND          AUDIT            AUDIT          WITTER
                                OF 82 DEAN      COMMITTEE MEMBER   COMMITTEES OF    COMMITTEES OF     FUNDS AND
NAME OF                           WITTER          OF 14 TCW/DW     82 DEAN WITTER     14 TCW/DW       14 TCW/DW
INDEPENDENT TRUSTEE               FUNDS              FUNDS             FUNDS            FUNDS           FUNDS
- ---------------------------  ----------------   ----------------   --------------   -------------   -------------
<S>                          <C>                <C>                <C>              <C>             <C>
Michael Bozic..............      $138,850           --                 --               --            $138,850
Edwin J. Garn..............       140,900           --                 --               --             140,900
John R. Haire..............       106,400           $64,283           $195,450        $ 12,187         378,320
Dr. Manuel H. Johnson......       137,100            66,483            --               --             203,583
Michael E. Nugent..........       138,850            64,283            --               --             203,133
John L. Schroeder..........       137,150            69,083            --               --             206,233
</TABLE>
 
    As  of the date of this Statement  of Additional Information, 57 of the Dean
Witter Funds, including the Fund, have adopted a retirement program under  which
an  Independent Trustee who  retires after serving  for at least  five years (or
such lesser period as may be determined by the Board) as an Independent Director
or Trustee of any Dean Witter Fund that has adopted the retirement program (each
such Fund referred to as an "Adopting Fund" and each such Trustee referred to as
an "Eligible  Trustee") is  entitled to  retirement payments  upon reaching  the
eligible  retirement age (normally, after attaining age 72). Annual payments are
based upon length of service. Currently, upon retirement, each Eligible  Trustee
is  entitled to  receive from  the Adopting  Fund, commencing  as of  his or her
retirement date and continuing for the remainder  of his or her life, an  annual
retirement benefit (the "Regular Benefit") equal to 25.0% of his or her Eligible
Compensation  plus 0.4166666% of such Eligible  Compensation for each full month
of service as an Independent Director or Trustee of any Adopting Fund in  excess
of five years up to a maximum of 50.0% after ten years of service. The foregoing
percentages may be changed by the Board.(1) "Eligible Compensation" is one-fifth
of  the total compensation  earned by such  Eligible Trustee for  service to the
Adopting Fund  in  the five  year  period prior  to  the date  of  the  Eligible
Trustee's  retirement. Benefits under the retirement  program are not secured or
funded by the Adopting Funds.
 
- ---------------
(1) An Eligible Trustee may  elect alternate payments of  his or her  retirement
    benefits  based upon the  combined life expectancy  of such Eligible Trustee
    and his or her spouse on the date of such Eligible Trustee's retirement. The
    amount estimated to be payable under  this method, through the remainder  of
    the  later of  the lives of  such Eligible  Trustee and spouse,  will be the
    actuarial equivalent  of  the Regular  Benefit.  In addition,  the  Eligible
    Trustee  may elect that the surviving  spouse's periodic payment of benefits
    will be equal  to either 50%  or 100%  of the previous  periodic amount,  an
    election  that, respectively,  increases or decreases  the previous periodic
    amount so that the  resulting payments will be  the actuarial equivalent  of
    the Regular Benefit.
 
                                       12
<PAGE>
    The  following  table illustrates  the  retirement benefits  accrued  to the
Fund's Independent Trustees by the Fund  for the fiscal year ended December  31,
1996  and by the  57 Dean Witter Funds  (including the Fund)  for the year ended
December 31,  1996,  and  the  estimated  retirement  benefits  for  the  Fund's
Independent  Trustees, to  commence upon their  retirement, from the  Fund as of
December 31, 1996 and from the 57 Dean Witter Funds as of December 31, 1996.
 
          RETIREMENT BENEFITS FROM THE FUND AND ALL DEAN WITTER FUNDS
 
<TABLE>
<CAPTION>
                                            FOR ALL ADOPTING FUNDS                RETIREMENT BENEFITS          ESTIMATED ANNUAL
                                    --------------------------------------        ACCRUED AS EXPENSES              BENEFITS
                                         ESTIMATED                                                            UPON RETIREMENT(2)
                                      CREDITED YEARS         ESTIMATED       -----------------------------   ---------------------
                                       OF SERVICE AT       PERCENTAGE OF                         BY ALL        FROM      FROM ALL
                                        RETIREMENT           ELIGIBLE           BY THE          ADOPTING        THE      ADOPTING
NAME OF INDEPENDENT TRUSTEE            (MAXIMUM 10)        COMPENSATION          FUND            FUNDS         FUND        FUNDS
- ----------------------------------  -------------------  -----------------   ------------     ------------   ---------   ---------
<S>                                 <C>                  <C>                 <C>              <C>            <C>         <C>
Michael Bozic.....................              10               50.0%       $        381     $     20,147   $     950   $  51,325
Edwin J. Garn.....................              10               50.0                 553           27,772         950      51,325
John R. Haire.....................              10               50.0                (282)(3)       46,952       2,343     129,550
Dr. Manuel H. Johnson.............              10               50.0                 231           10,926         950      51,325
Michael E. Nugent.................              10               50.0                 396           19,217         950      51,325
John L. Schroeder.................               8               41.7                 736           38,700         792      42,771
</TABLE>
 
- ---------------
(2) Based on  current levels  of compensation.  Amount of  annual benefits  also
    varies depending on the Trustee's elections described in Footnote (1) above.
(3) This  number reflects  the effect  of the extension  of Mr.  Haire's term as
    Trustee until June 1, 1998.
 
    As of the date  of this Statement of  Additional Information, the  aggregate
number of shares of beneficial interest of the Fund owned by the Fund's officers
and  Trustees  as a  group  was less  than  1 percent  of  the Fund's  shares of
beneficial interest outstanding.
 
INVESTMENT PRACTICES AND POLICIES
- --------------------------------------------------------------------------------
 
    As discussed in  the Prospectus,  the Fund  may only  invest 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.
 
    ZERO  COUPON  SECURITIES.    A portion  of  the  U.S.  Government securities
purchased by the  Fund may be  "zero coupon" Treasury  securities with  maturity
dates  in each  case no later  than ten years  from the settlement  date for the
purchase of such security. These are U.S. Treasury bills, notes and bonds  which
have been stripped of their unmatured interest coupons and receipts or which are
certificates  representing  interests  in  such  stripped  debt  obligations and
coupons. "Zero coupon" securities  are purchased at a  discount from their  face
amount,  giving the purchaser the right to receive their full value at maturity.
A zero coupon security pays no interest to its holder during its life. Its value
to an investor consists of the difference between its face value at the time  of
maturity  and the price for which it  was acquired, which is generally an amount
significantly less  than  its face  value  (sometimes  referred to  as  a  "deep
discount" price).
 
    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 if
prevailing  interest rates  rise. For  this reason,  zero coupon  securities are
subject to substantially  greater market  price fluctuations  during periods  of
changing  prevailing interest  rates than  are comparable  debt securities which
make current distributions of interest. 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.
 
                                       13
<PAGE>
INVESTMENT RESTRICTIONS
- --------------------------------------------------------------------------------
 
    The investment restrictions listed  below have been adopted  by the Fund  as
fundamental policies, which may not be changed without the vote of a majority of
the  outstanding voting securities  of the Fund,  as defined in  the Act. Such a
majority is defined as the lesser of (a) 67% of the shares present at a  meeting
of  shareholders, if the holders  of more than 50%  of the outstanding shares of
the Fund  are present  or represented  by proxy,  or (b)  more than  50% of  the
outstanding  shares of the Fund. For  purposes of the following restrictions (a)
an "issuer" of a security is the entity whose assets and revenues are  committed
to  the payment of interest and  principal on that particular security, provided
that the guarantee of a security will be considered a separate security; and (b)
all percentage  limitations  apply  immediately  after  a  purchase  or  initial
investment,  and any  subsequent change  in any  applicable percentage resulting
from market  fluctuations or  other changes  in  total or  net assets  does  not
require elimination of any security from the portfolio.
 
    The Fund may not:
 
         1.  Purchase any securities other than obligations issued or guaranteed
    by the United  States Government. Such  obligations are backed  by the  full
    faith  and credit of the  United States. There is no  limit on the amount of
    its assets which may be invested in the securities of any one issuer of such
    obligations.
 
         2. Borrow money except from banks for temporary or emergency  purposes,
    including  the meeting of redemption  requests which might otherwise require
    the untimely disposition of securities.  Borrowing in the aggregate may  not
    exceed  20%, and borrowing  for purposes other  than meeting redemptions may
    not exceed 5%, of the value of the Fund's total assets (including the amount
    borrowed) at  the time  the borrowing  is  made. It  is the  Fund's  current
    intention  not  to  borrow  for  other  than  meeting  redemptions requests.
    Borrowings in excess of 5% will be repaid before additional investments  are
    made. Interest on borrowings will reduce net investment income.
 
         3.  Pledge,  hypothecate, mortgage  or  otherwise encumber  its assets,
    except in an amount  not exceeding 10%  of the value of  its net assets  but
    only to secure borrowings for temporary or emergency purposes.
 
         4. Sell securities short or purchase securities on margin.
 
         5. Make loans to others except through the purchase of debt obligations
    in accordance with the Fund's investment objective and policies.
 
         6.  Issue senior securities as defined in the Act except insofar as the
    Fund may be  deemed to have  a senior  security by reason  of (a)  borrowing
    money  in  accordance  with  restriction  (2)  described  above,  or  (b) by
    purchasing  securities  on  a  when-issued  or  delayed  delivery  basis  or
    purchasing or selling securities on a forward commitment basis.
 
         7.  Underwrite the securities  of other issuers  or purchase restricted
    securities.
 
         8. Purchase or sell real estate or interests therein, although the Fund
    may purchase securities of  issuers which engage  in real estate  operations
    and securities which are secured by real estate or interests therein.
 
    Notwithstanding  any other  investment policy  or restriction,  the Fund may
seek to achieve its investment objective  by investing all or substantially  all
of  its  assets  in another  investment  company having  substantially  the same
investment objective and policies as the Fund.
 
PORTFOLIO TRANSACTIONS AND BROKERAGE
- --------------------------------------------------------------------------------
 
    Subject to the general supervision of the Board of Trustees of the Fund, the
Investment Manager is responsible for  the investment decisions and the  placing
of  the orders  for portfolio  transactions for  the Fund.  The Fund's portfolio
transactions will occur primarily with issuers, underwriters or major dealers in
 
                                       14
<PAGE>
U.S. Government Securities acting as principals. Such transactions are  normally
on  a net basis which do not  involve payment of brokerage commissions. The cost
of securities purchased from an  underwriter usually includes a commission  paid
by  the issuer to  the underwriters; transactions  with dealers normally reflect
the spread between bid and asked prices. During the fiscal years ended  December
31, 1994, 1995 and 1996, the Fund did not pay any brokerage commissions.
 
   
    The Investment Manager currently serves as investment manager to a number of
clients,  including other  investment companies,  and may  in the  future act as
investment manager or adviser  to others. It is  the practice of the  Investment
Manager  to cause purchase and sale transactions  to be allocated among the Fund
and others whose  assets it manages  in such  manner as it  deems equitable.  In
making  such  allocations  among the  Fund  and other  client  accounts, various
factors may be considered, including  the respective investment objectives,  the
relative  size of portfolio  holdings of the same  or comparable securities, the
availability  of  cash  for  investment,  the  size  of  investment  commitments
generally  held and  the opinions  of the  persons responsible  for managing the
portfolios of the Fund and other client accounts. In the case of certain initial
and secondary public offerings,  the Investment Manager may  utilize a pro  rata
allocation  process based on the size of  the Dean Witter Funds involved and the
number of shares available from the public offering.
    
 
    The policy of the Fund, regarding purchases and sales of securities for  its
portfolio,  is  that  primary  consideration  be  given  to  obtaining  the most
favorable  prices  and  efficient  execution  of  transactions.  In  seeking  to
implement  the Fund's policies, the Investment Manager effects transactions with
those brokers and dealers who the  Investment Manager believes provide the  most
favorable  prices  and are  capable of  providing  efficient executions.  If the
Investment Manager believes such prices and executions are obtainable from  more
than  one  broker or  dealer,  it may  give  consideration to  placing portfolio
transactions with those brokers and dealers who also furnish research and  other
services  to the Fund or the Investment  Manager. Such services may include, but
are not limited  to, any one  or more of  the following: information  as to  the
availability  of  securities  for  purchase  or  sale;  statistical  or  factual
information or opinions pertaining to investment; wire services; and  appraisals
or evaluations of portfolio securities.
 
    The information and services received by the Investment Manager from brokers
and  dealers may be  of benefit to  the Investment Manager  in the management of
accounts of some of its  other clients and may not,  in every case, benefit  the
Fund  directly. While the receipt of such  information and services is useful in
varying degrees and would  generally reduce the amount  of research or  services
otherwise  performed by the Investment Manager  and thereby reduce its expenses,
it is of indeterminable value and the Fund does not reduce the management fee it
pays to the Investment  Manager by any  amount that may  be attributable to  the
value of such services.
 
   
    Pursuant to an order of the Securities and Exchange Commission, the Fund may
effect  principal transactions in certain money market instruments with DWR. The
Fund will limit its  transactions with DWR to  U.S. Government Securities.  Such
transactions will be effected with DWR only when the price available from DWR is
better  than that  available from other  dealers. During the  fiscal years ended
December 31,  1994,  1995  and 1996,  the  Fund  did not  effect  any  principal
transactions with DWR.
    
 
   
    Consistent  with  the  policy  described  above,  brokerage  transactions in
securities listed on exchanges or admitted to unlisted trading privileges may be
effected through DWR and other affiliated  brokers and dealers. In order for  an
affiliated  broker or dealer to effect  portfolio transactions for the Fund, the
commissions, fees or  other remuneration  received by the  affiliated broker  or
dealer  must be reasonable and  fair compared to the  commissions, fees or other
remuneration paid to  other brokers in  connection with comparable  transactions
involving  similar securities  being purchased or  sold on an  exchange during a
comparable period of time.  This standard would allow  the affiliated broker  or
dealer  to receive no more  than the remuneration which  would be expected to be
received by an unaffiliated broker  in a commensurate arm's-length  transaction.
Furthermore,  the Trustees of the Fund, including a majority of the Trustees who
are not  "interested" Trustees,  have adopted  procedures which  are  reasonably
designed  to provide that any commissions, fees or other remuneration paid to an
affiliated broker or dealer are consistent with the foregoing standard. For  the
fiscal years ended December 31, 1994, 1995 and 1996, the Fund did not effect any
securities transactions through any affiliated brokers or dealers.
    
 
                                       15
<PAGE>
THE DISTRIBUTOR
- --------------------------------------------------------------------------------
 
   
    As  discussed in the Prospectus, shares of  the Fund are distributed by Dean
Witter Distributors Inc. (the "Distributor"). The Distributor has entered into a
selected dealer agreement  with DWR,  which through its  own sales  organization
sells  shares of the Fund. In addition,  the Distributor may enter into selected
dealer  agreements  with  other  selected  broker-dealers.  The  Distributor,  a
Delaware  corporation, is a  wholly-owned subsidiary of  MSDWD. The Trustees who
are not, and were not at the time they voted, interested persons of the Fund, as
defined in the Act (the "Independent Trustees"), approved, at their meeting held
on June 30, 1997, the current Distribution Agreement appointing the  Distributor
as  exclusive distributor of the Fund's shares and providing for the Distributor
to bear  distribution  expenses  not  borne  by the  Fund.  By  its  terms,  the
Distribution Agreement has an initial term ending April 30, 1998 and will remain
in effect from year to year thereafter if approved by the Board.
    
 
    The  Distributor bears all expenses incurred in providing services under the
Distribution Agreement. Such  expenses include  the payment  of commissions  for
sales of the Fund's shares and incentive compensation to account executives. The
Distributor  also pays certain  expenses in connection  with the distribution of
the Fund's shares, including the  costs of preparing, printing and  distributing
advertising or promotional materials, and the costs of printing and distributing
prospectuses  and supplements thereto  used in connection  with the offering and
sale of the Fund's shares to other than current shareholders. The Fund bears the
costs of  initial typesetting,  printing and  distribution of  prospectuses  and
supplements   thereto  to  shareholders.  The  Fund  also  bears  the  costs  of
registering the  Fund and  its shares  under federal  securities laws  and  pays
filing  fees  in  accordance  with  state  securities  laws.  The  Fund  and the
Distributor have agreed  to indemnify  each other  against certain  liabilities,
including  liabilities under the  Securities Act of 1933,  as amended. Under the
Distribution Agreement,  the  Distributor uses  its  best efforts  in  rendering
services  to the  Fund, but  in the absence  of willful  misfeasance, bad faith,
gross negligence or reckless  disregard of its  obligations, the Distributor  is
not  liable to the Fund or any of  its shareholders for any error of judgment or
mistake of law or  for any act or  omission or for any  losses sustained by  the
Fund or its shareholders.
 
PLAN OF DISTRIBUTION
 
   
    The Fund has adopted a Plan of Distribution pursuant to Rule 12b-1 under the
Act  (the "Plan")  pursuant to which  each Class,  other than Class  D, pays the
Distributor compensation  accrued daily  and payable  monthly at  the  following
annual  rates: 0.25% and  0.75% of the average  daily net assets  of Class A and
Class C, respectively,  and, with respect  to Class B,  0.75% (0.65% of  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 contingent deferred sales charge has been imposed
or upon which such charge has been  waived, or (b) the average daily net  assets
of  the  Fund. The  Distributor also  receives the  proceeds of  front-end sales
charges and of contingent deferred sales charges imposed on certain  redemptions
of  shares, which are separate and apart from payments made pursuant to the Plan
(see "Purchase of Fund Shares" in the Prospectus). The Distributor has  informed
the  Fund that it and/or DWR received approximately $23,000,000, $10,629,000 and
$8,964,262 in  contingent deferred  sales  charges for  the fiscal  years  ended
December  31, 1994, 1995 and  1996, respectively, none of  which was retained by
the Distributor.
    
 
   
    The Distributor has informed the Fund that the entire fee payable by Class A
and a portion  of the fees  payable by  each of Class  B and Class  C each  year
pursuant  to the Plan 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"  under the  Rules of  the Association  of the
National Association of Securities Dealers, Inc. (of which the Distributor is  a
member).  The "service fee"  is a payment  made for personal  service and/or the
maintenance of  shareholder accounts.  The remaining  portion of  the Plan  fees
payable by a Class, if any, is characterized as an "asset-based sales charge" as
such is defined by the aforementioned Rules of the Association.
    
 
                                       16
<PAGE>
    The  Plan was adopted by a majority vote of the Board of Trustees, including
all of the Trustees of the Fund who are not "interested persons" of the Fund (as
defined in the Act) and who have no direct or indirect financial interest in the
operation of the Plan  (the "Independent 12b-1 Trustees"),  cast in person at  a
meeting  called for the purpose of voting on the Plan, on April 16, 1984, by DWR
as the then sole shareholder of the Fund on May 1, 1984, and by the shareholders
holding a majority, as defined in the Act, of the outstanding voting  securities
of the Fund at a Meeting of Shareholders of the Fund held on April 22, 1985.
 
   
    At  their  meeting held  on  October 30,  1992,  the Trustees  of  the Fund,
including all of the Independent 12b-1 Trustees, approved certain amendments  to
the  Plan which took  effect in January,  1993 and were  designed to reflect the
fact that  upon  the  reorganization  described  above  the  share  distribution
activities  theretofore  performed  for the  Fund  by  DWR were  assumed  by the
Distributor and DWR's sales activities are  now being performed pursuant to  the
terms  of  a selected  dealer  agreement between  the  Distributor and  DWR. The
amendments provide that payments under the Plan will be made to the  Distributor
rather  than to DWR as before the amendment, and that the Distributor in turn is
authorized  to  make  payments  to   DWR,  its  affiliates  or  other   selected
broker-dealers  (or  direct  that  the Fund  pay  such  entities  directly). The
Distributor is also authorized  to retain part of  such fee as compensation  for
its  own distribution-related expenses. At their meeting held on April 28, 1993,
the Trustees, including a majority  of the Independent 12b-1 Trustees,  approved
certain  technical amendments to the Plan  in connection with amendments adopted
by the National  Association of  Securities Dealers, Inc.  to its  Rules of  the
Association.  At their  meeting held  on October 26,  1995, the  Trustees of the
Fund, including all of the Independent 12b-1 Trustees, approved an amendment  to
the  Plan to permit payments  to be made under the  Plan with respect to certain
distribution expenses incurred  in connection with  the distribution of  shares,
including  personal services  to shareholders with  respect to  holdings of such
shares, of an  investment company whose  assets are  acquired by the  Fund in  a
tax-free  reorganization. At their meeting held  on June 30, 1997, the Trustees,
including a majority of the  Independent 12b-1 Trustees, approved amendments  to
the Plan to reflect the multiple-class structure for the Fund, which took effect
on July 28, 1997.
    
 
    Under  the Plan  and as  required by  Rule 12b-1,  the Trustees  receive and
review promptly after the end of each calendar quarter a written report provided
by the Distributor of the amounts expended by the Distributor under the Plan and
the purpose for  which such  expenditures were  made. The  Fund accrued  amounts
payable to the Distributor under the Plan, during the fiscal year ended December
31, 1996, of $53,189,389. This amount is equal to 0.75% of the average daily net
assets of the Fund for the fiscal year and was calculated pursuant to clause (b)
under  the Plan. This amount is treated by the Fund as an expense in the year it
is accrued. This amount represents amounts paid  by Class B only; there were  no
Class A or Class C shares outstanding on such date.
 
    The  Plan was adopted  in order to  permit the implementation  of the Fund's
method of  distribution. Under  this distribution  method the  Fund offers  four
Classes  of shares, each with a  different distribution arrangement as set forth
in the Prospectus.
 
    With respect to Class  A shares, DWR compensates  its account executives  by
paying  them, from proceeds  of the front-end sales  charge, commissions for the
sale of Class  A shares, currently  a gross sales  credit of up  to 4.0% of  the
amount  sold  (except  as provided  in  the  following sentence)  and  an annual
residual commission, currently a residual of up to 0.20% of the current value of
the respective accounts for which they are the account executives or dealers  of
record  in all cases. On orders of $1 million or more (for which no sales charge
was  paid)   or  net   asset  value   purchases  by   401(k)  plans   or   other
employer-sponsored  plans qualified under Section 401(a) of the Internal Revenue
Code for  which Dean  Witter Trust  Company ("DWTC")  or Dean  Witter Trust  FSB
("DWTFSB")  serves as Trustee or the 401(k) Support Services Group of DWR serves
as recordkeeper, the Investment Manager compensates DWR's account executives  by
paying  them, from  its own funds,  a gross sales  credit of 1.0%  of the amount
sold.
 
    With respect to Class  B shares, DWR compensates  its account executives  by
paying  them, from its  own funds, commissions  for the sale  of Class B shares,
currently   a    gross    sales    credit    of    up    to    4.0%    of    the
 
                                       17
<PAGE>
amount  sold  (except  as provided  in  the  following sentence)  and  an annual
residual commission, currently a  residual of up to  0.20% of the current  value
(not  including reinvested dividends or distributions) of the amount sold in all
cases. In the  case of retirement  plans qualified under  Section 401(k) of  the
Internal Revenue Code and other employer-sponsored plans qualified under Section
401(a)  of the Internal Revenue Code for  which DWTC or DWTFSB serves as Trustee
or the 401(k) Support  Services Group of DWR  serves as recordkeeper, and  which
plans  are  opened  on or  after  July  28, 1997,  DWR  compensates  its account
executives by paying them, from its own  funds, a gross sales credit of 3.0%  of
the amount sold.
 
   
    With  respect to Class  C shares, DWR compensates  its account executives by
paying them, from its  own funds, commissions  for the sale  of Class C  shares,
currently  a gross sales credit of  up to 1.0% of the  amount sold and an annual
residual commission, currently a residual of up to 0.75% of the current value of
the respective accounts for which they are the account executives of record.
    
 
    With respect to Class D shares other than shares held by participants in the
InterCapital mutual  fund  asset  allocation  program,  the  Investment  Manager
compensates  DWR's  account  executives  by paying  them,  from  its  own funds,
commissions for the sale of Class D shares, currently a gross sales credit of up
to 1.0% of the amount sold. There is a chargeback of 100% of the amount paid  if
the Class D shares are redeemed in the first year and a chargeback of 50% of the
amount  paid  if  the Class  D  shares are  redeemed  in the  second  year after
purchase. The Investment  Manager also compensates  DWR's account executives  by
paying  them, from  its own  funds, an  annual residual  commission, currently a
residual of up  to 0.10% of  the current  value of the  respective accounts  for
which  they  are the  account executives  of record  (not including  accounts of
participants in the InterCapital mutual fund asset allocation program).
 
    The gross sales credit is a charge which reflects commissions paid by DWR to
its account executives and DWR's Fund associated distribution-related  expenses,
including   sales   compensation   and   overhead   and   other   branch  office
distribution-related expenses  including: (a)  the expenses  of operating  DWR's
branch  offices  in connection  with the  sale of  Fund shares,  including lease
costs, the  salaries  and employee  benefits  of operations  and  sales  support
personnel,  utility costs, communications costs and  the costs of stationery and
supplies, (b) the costs of client sales seminars, (c) travel expenses of  mutual
fund  sales  coordinators to  promote  the sale  of  Fund shares  and  (d) other
expenses relating to branch promotion of Fund share sales. The distribution  fee
that  the Distributor receives from the Fund  under the Plan, in effect, offsets
distribution expenses incurred under the Plan on behalf of the Fund and, in  the
case of Class B shares, opportunity costs, such as the gross sales credit and an
assumed  interest  charge  thereon  ("carrying  charge").  In  the Distributor's
reporting of the  distribution expenses  to the  Fund, in  the case  of Class  B
shares,  such assumed interest  (computed at the "broker's  call rate") has been
calculated on the gross sales credit as it is reduced by amounts received by the
Distributor under the Plan and any contingent deferred sales charges received by
the Distributor upon redemption of shares of the Fund. No other interest  charge
is  included as a  distribution expense in the  Distributor's calculation of its
distribution costs for this purpose. The broker's call rate is the interest rate
charged to securities brokers on loans secured by exchange-listed securities.
 
    The Fund paid 100% of the $53,189,389 accrued under the Plan for the  fiscal
year  ended  December  31, 1996  to  the  Distributor. The  Distributor  and DWR
estimate that they have spent, pursuant to the Plan, $1,150,496,391 on behalf of
the Fund since the inception of the  Plan. It is estimated that this amount  was
spent  in approximately the following  ways: (i) 0.59% ($6,764,961)--advertising
and promotional expenses; (ii) 0.12% ($1,386,515)--printing of prospectuses  for
distribution   to   other   than   current   shareholders;   and   (iii)  99.29%
($1,142,344,915)--other expenses,  including  the  gross sales  credit  and  the
carrying  charge, of  which 14.97%  ($171,001,978) represents  carrying charges,
34.96% ($399,319,081) represents  commission credits to  DWR branch offices  for
payments   of  commissions  to  account  executives  and  50.07%  ($572,023,856)
represents overhead and other branch office distribution-related expenses. These
amounts represent amounts paid by Class B only; there were no Class A or Class C
shares outstanding on such date.
 
                                       18
<PAGE>
    The Fund is authorized to reimburse  expenses incurred or to be incurred  in
promoting  the distribution  of the  Fund's Class  A and  Class C  shares and in
servicing shareholder accounts. Reimbursement will  be made through payments  at
the end of each month. The amount of each monthly payment may in no event exceed
an  amount equal to a payment at the annual  rate of 0.25%, in the case of Class
A, and  0.75%,  in the  case  of Class  C,  of the  average  net assets  of  the
respective  Class during the  month. No interest or  other financing charges, if
any, incurred on any distribution expenses on behalf of Class A and Class C will
be reimbursable under  the Plan. With  respect to Class  A, in the  case of  all
expenses  other than expenses representing the service fee, and, with respect to
Class C, in the case  of all expenses other  than expenses representing a  gross
sales  credit  or  a  residual  to account  executives,  such  amounts  shall be
determined at the beginning of each calendar quarter by the Trustees,  including
a  majority of the Independent 12b-1 Trustees. Expenses representing the service
fee (for Class A) or  a gross sales credit or  a residual to account  executives
(for  Class C) may be reimbursed without  prior determination. In the event that
the Distributor proposes  that monies shall  be reimbursed for  other than  such
expenses,  then in  making quarterly determinations  of the amounts  that may be
reimbursed by  the Fund,  the Distributor  will provide  and the  Trustees  will
review  a quarterly budget of projected  distribution expenses to be incurred on
behalf of  the  Fund,  together  with  a  report  explaining  the  purposes  and
anticipated  benefits of  incurring such  expenses. The  Trustees will determine
which particular expenses, and  the portions thereof, that  may be borne by  the
Fund,  and  in making  such  a determination  shall  consider the  scope  of the
Distributor's commitment to promoting the distribution of the Fund's Class A and
Class C shares.
 
    At any given time, the  expenses of distributing shares  of the Fund may  be
more or less than the total of (i) the payments made by the Fund pursuant to the
Plan  and  (ii)  the  proceeds  of contingent  deferred  sales  charges  paid by
investors upon redemption of shares. The  Distributor has advised the Fund  that
in the case of Class B shares the excess expenses, including the carrying charge
designed  to approximate the opportunity costs  incurred by DWR which arise from
it having  advanced monies  without  having received  the  amount of  any  sales
charges  imposed at  the time  of sale  of the  Fund's Class  B shares, totalled
$68,120,003 as of December 31, 1996.  Because there is no requirement under  the
Plan  that  the Distributor  be reimbursed  for  all distribution  expenses with
respect to Class B  shares or any  requirement that the  Plan be continued  from
year  to year, this 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
contingent deferred sales charges 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 contingent deferred
sales  charges, may or may not be  recovered through future distribution fees or
contingent deferred sales charges.
 
    No interested person of the Fund nor any  Trustee of the Fund who is not  an
interested  person of the Fund, as defined  in the Act, has any direct financial
interest in the operation of the Plan except to the extent that the Distributor,
InterCapital, DWSC, DWR, or  certain of their employees,  may be deemed to  have
such  an interest as a result of  benefits derived from the successful operation
of the  Plan or  as a  result of  receiving a  portion of  the amounts  expended
thereunder by the Fund.
 
    Under  its terms, the Plan had an  initial term ending December 31, 1984 and
will continue  from  year  to  year thereafter,  provided  such  continuance  is
approved annually by a vote of the Trustees in the manner described above. Prior
to  the Board's approval of amendments to the Plan to reflect the multiple-class
structure for the Fund, the  most recent continuance of  the Plan for one  year,
until  April  30, 1998,  was  approved by  the Board  of  Trustees of  the Fund,
including a majority of the Independent 12b-1 Trustees, at a Board meeting  held
on April 24, 1997. Prior to approving the continuation of the Plan, the Trustees
requested  and received  from the Distributor  and reviewed  all the information
which they deemed necessary  to arrive at an  informed determination. In  making
their  determination  to continue  the Plan,  the  Trustees considered:  (1) the
Fund's experience under the Plan and whether such experience indicates that  the
Plan  is operating as anticipated;  (2) the benefits the  Fund had obtained, was
obtaining and would be likely  to obtain under the  Plan; and (3) what  services
had  been provided and were continuing to be provided under the Plan to the Fund
and its shareholders. Based upon their review, the
 
                                       19
<PAGE>
Trustees of  the  Fund,  including  each  of  the  Independent  12b-1  Trustees,
determined  that continuation of the  Plan would be in  the best interest of the
Fund and would have  a reasonable likelihood of  continuing to benefit the  Fund
and  its shareholders. In the Trustees' quarterly  review of the Plan, they will
consider its continued  appropriateness and the  level of compensation  provided
herein.
 
    The  Plan may not be  amended to increase materially  the amount to be spent
for the services described therein without  approval by the shareholders of  the
affected  Class or Classes of the Fund,  and all material amendments to the Plan
must also be approved by  the Trustees in the  manner described above. The  Plan
may  be terminated  at any time,  without payment of  any penalty, by  vote of a
majority of the Independent  12b-1 Trustees or  by a vote of  a majority of  the
outstanding  voting securities of the  Fund (as defined in  the Act) on not more
than thirty days' written notice to any other party to the Plan. So long as  the
Plan  is in  effect, the election  and nomination of  Independent 12b-1 Trustees
shall be committed to the discretion of the Independent 12b-1 Trustees.
 
DETERMINATION OF NET ASSET VALUE
- --------------------------------------------------------------------------------
 
    As stated in the Prospectus, short-term securities with remaining maturities
of sixty days  or less at  the time of  purchase are valued  at amortized  cost,
unless  the  Trustees determine  such does  not  reflect the  securities' market
value, in which  case these securities  will be  valued at their  fair value  as
determined by the Trustees. Other short-term debt securities will be valued on a
mark-to-market basis until such time as they reach a remaining maturity of sixty
days,  whereupon they will be valued at  amortized cost using their value on the
61st day unless  the Trustees determine  such does not  reflect the  securities'
market  value, in which case these securities will be valued at their fair value
as determined by the Trustees. All other securities and other assets are  valued
at  their fair value as determined in good faith under procedures established by
and under the supervision of the Trustees.
 
    The net  asset value  per share  for each  Class of  shares of  the Fund  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. The New York Stock Exchange  currently
observes  the following holidays: New Year's  Day; Presidents' Day; Good Friday;
Memorial Day; Independence Day; Labor Day; Thanksgiving Day; and Christmas Day.
 
PURCHASE OF FUND SHARES
- --------------------------------------------------------------------------------
 
    As discussed in the  Prospectus, the Fund offers  four Classes of shares  as
follows:
 
INITIAL SALES CHARGE ALTERNATIVE--CLASS A SHARES
 
    Class  A shares  are sold  to investors  with an  initial sales  charge that
declines to zero for larger purchases;  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 in the  circumstances
discussed in the Prospectus.
 
   
    RIGHT  OF  ACCUMULATION.   As  discussed  in the  Prospectus,  investors may
combine the  current value  of  shares purchased  in separate  transactions  for
purposes  of benefitting from the reduced  sales charges available for purchases
of shares  of the  Fund  totalling at  least $25,000  in  net asset  value.  For
example,  if any person or entity who qualifies for this privilege holds Class A
shares of the Fund and/or other Dean Witter Funds that are multiple class  funds
("Dean Witter Multi-Class Funds") or shares of other Dean Witter Funds sold with
a front-end sales charge purchased at a price including a front-end sales charge
having  a current value of $5,000, and purchases $20,000 of additional shares of
the Fund, the sales charge applicable to  the $20,000 purchase would be 4.0%  of
the offering price.
    
 
    The  Distributor  must  be notified  by  the 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  selected  broker-dealer or  shareholder  when
 
                                       20
<PAGE>
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 Distributor  or Dean  Witter Trust  Company (the
"Transfer Agent") fails to confirm the investor's represented holdings.
 
    LETTER OF INTENT.  As discussed in the Prospectus, reduced sales charges are
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
the Distributor or from a single Selected Broker-Dealer.
 
    A  Letter of Intent permits an investor to establish a total investment goal
to be achieved  by any number  of purchases over  a thirteen-month period.  Each
purchase of Class A shares made during the period will receive the reduced sales
commission  applicable to the  amount represented by  the goal, as  if it were a
single purchase. A number of shares equal in value to 5% of the dollar amount of
the Letter of Intent will be held in  escrow by the Transfer Agent, in the  name
of  the shareholder. The initial purchase under a Letter of Intent must be equal
to at least 5% of the stated investment goal.
 
    The Letter of  Intent does not  obligate the investor  to purchase, nor  the
Fund  to sell, the indicated  amount. In the event the  Letter of Intent goal is
not achieved within the thirteen-month period,  the investor is required to  pay
the  difference between the  sales charge otherwise  applicable to the purchases
made during this  period and sales  charges actually paid.  Such payment may  be
made  directly to the Distributor or, if not paid, the Distributor is authorized
by the  shareholder to  liquidate a  sufficient number  of his  or her  escrowed
shares to obtain such difference.
 
   
    If  the goal is exceeded and purchases pass the next sales charge level, the
sales charge on the entire amount of  the purchase that results in passing  that
level  and  on subsequent  purchases will  be subject  to further  reduced sales
charges in the same manner as set forth above under "Right of Accumulation," but
there will be no retroactive reduction  of sales charges on previous  purchases.
For  the purpose of  determining whether the  investor is entitled  to a further
reduced sales charge applicable  to purchases at or  above a sales charge  level
which  exceeds the stated goal of a Letter of Intent, the cumulative current net
asset value of any shares owned by  the investor in any other Dean Witter  Funds
held  by the shareholder which were previously  purchased at a price including a
front-end sales charge (including shares of the Fund and other Dean Witter Funds
acquired in  exchange  for those  shares,  and  including in  each  case  shares
acquired  through reinvestment of dividends and  distributions) will be added to
the cost  or net  asset value  of  shares of  the Fund  owned by  the  investor.
However,   shares  of  "Exchange  Funds"  (see  "Shareholder  Services--Exchange
Privilege") and the purchase of  shares of other Dean  Witter Funds will not  be
included  in determining whether the stated goal  of a Letter of Intent has been
reached.
    
 
    At any time while  a Letter of  Intent is in effect,  a shareholder may,  by
written  notice to the Distributor,  increase the amount of  the stated goal. In
that event, only shares  purchased during the previous  90-day period and  still
owned by the shareholder will be included in the new sales charge reduction. The
5% escrow and minimum purchase requirements will be applicable to the new stated
goal.  Investors electing to purchase shares of the Fund pursuant to a Letter of
Intent should carefully read such Letter of Intent.
 
CONTINGENT DEFERRED SALES CHARGE ALTERNATIVE--CLASS B SHARES
 
    Class B shares are sold without an initial sales charge but are subject to a
CDSC payable upon most redemptions within six years after purchase. As stated in
the Prospectus, a CDSC will be imposed on any redemption by an investor if after
such redemption the current value of the  investor's Class B shares of the  Fund
is  less  than the  dollar amount  of all  payments by  the shareholder  for the
purchase of Class B shares  during the preceding six years  (or, in the case  of
shares  held by certain employer-sponsored benefit plans, three years). However,
no CDSC will be  imposed to the extent  that the net asset  value of the  shares
redeemed  does not exceed: (a)  the current net asset  value of shares purchased
more  than   six  years   (or,  in   the  case   of  shares   held  by   certain
employer-sponsored benefit plans, three years) prior to the redemption, plus (b)
the  current  net  asset  value  of  shares  purchased  through  reinvestment of
dividends or  distributions  of  the  Fund or  another  Dean  Witter  Fund  (see
"Shareholder Services--
 
                                       21
<PAGE>
   
Targeted Dividends"), plus (c) the current net asset value of shares acquired in
exchange  for (i) shares  of Dean Witter  front-end sales charge  funds, or (ii)
shares of other  Dean Witter Funds  for which shares  of front-end sales  charge
funds have been exchanged (see "Shareholder Services--Exchange Privilege"), plus
(d)  increases in the net  asset value of the  investor's shares above the total
amount of payments for the purchase of Fund shares made during the preceding six
(three) years. The CDSC will be paid to the Distributor.
    
 
    In determining the applicability of the CDSC to each redemption, the  amount
which  represents an increase  in the net  asset value of  the investor's shares
above the amount of  the total payments  for the purchase  of shares within  the
last  six years (or,  in the case  of shares held  by certain employer-sponsored
benefit plans, three years) will be redeemed first. In the event the  redemption
amount  exceeds such increase in value, the  next portion of the amount redeemed
will be the amount which represents the net asset value of the investor's shares
purchased more than  six (three)  years prior  to the  redemption and/or  shares
purchased  through  reinvestment  of dividends  or  distributions  and/or shares
acquired in exchange for shares of Dean Witter front-end sales charge funds,  or
for shares of other Dean Witter funds for which shares of front-end sales charge
funds  have been exchanged.  A portion of  the amount redeemed  which exceeds an
amount which represents  both such  increase in value  and the  value of  shares
purchased  more  than six  years  (or, in  the case  of  shares held  by certain
employer-sponsored benefit plans,  three years) prior  to the redemption  and/or
shares  purchased  through  reinvestment of  dividends  or  distributions and/or
shares acquired in the above-described exchanges will be subject to a CDSC.
 
    The amount of the CDSC, if any,  will vary depending on the number of  years
from  the time of payment for  the purchase of Class B  shares of the Fund until
the time of redemption of such shares. For purposes of determining the number of
years from the time of any payment for the purchase of shares, all payments made
during a month will be aggregated and deemed  to have been made on the last  day
of the month. The following table sets forth the rates of the CDSC applicable to
most Class B shares of the Fund:
 
<TABLE>
<CAPTION>
                                                                                            CDSC AS A
                                        YEAR SINCE                                          PERCENTAGE
                                         PURCHASE                                           OF AMOUNT
                                       PAYMENT MADE                                         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>
 
    The  following table sets forth the rates  of the CDSC applicable to Class B
shares of  the Fund  held  by 401(k)  plans  or other  employer-sponsored  plans
qualified  under Section 401(a) of  the Internal Revenue Code  for which DWTC or
DWTFSB serves as Trustee or the 401(k)  Support Services Group of DWR serves  as
recordkeeper and whose accounts are opened on or after July 28, 1997:
 
<TABLE>
<CAPTION>
                                                                                            CDSC AS A
                                        YEAR SINCE                                          PERCENTAGE
                                         PURCHASE                                           OF AMOUNT
                                       PAYMENT MADE                                         REDEEMED
- ------------------------------------------------------------------------------------------  ---------
<S>                                                                                         <C>
First.....................................................................................       2.0%
Second....................................................................................       2.0%
Third.....................................................................................       1.0%
Fourth and thereafter.....................................................................    None
</TABLE>
 
    In determining the rate of the CDSC, it will be assumed that a redemption is
made  of shares held by  the investor for the longest  period of time within the
applicable six-year or  three-year period.  This will  result in  any such  CDSC
being  imposed  at  the lowest  possible  rate.  The CDSC  will  be  imposed, in
 
                                       22
<PAGE>
accordance with the table shown above, on any redemptions within six years  (or,
in  the case of  shares held by certain  employer-sponsored benefit plans, three
years) of purchase which are in excess of these amounts and which redemptions do
not qualify for waiver of the CDSC, as described in the Prospectus.
 
LEVEL LOAD ALTERNATIVE--CLASS C SHARES
 
    Class C shares are sold without a sales charge but are subject to a CDSC  of
1.0%  on most  redemptions made  within one year  after purchase,  except in the
circumstances discussed in the Prospectus.
 
NO LOAD ALTERNATIVE--CLASS D SHARES
 
    Class D  shares  are  offered  without  any  sales  charge  on  purchase  or
redemption.  Class  D  shares are  offered  only  to those  persons  meeting the
qualifications set forth in the Prospectus.
 
SHAREHOLDER SERVICES
- --------------------------------------------------------------------------------
 
    Upon the purchase of shares of the Fund, a Shareholder Investment Account is
opened for the investor on the books of the Fund and maintained by the  Transfer
Agent.  This  is an  open  account in  which shares  owned  by the  investor are
credited by the Transfer Agent in lieu of issuance of a share certificate. If  a
share  certificate  is  desired,  it  must  be  requested  in  writing  for each
transaction. Certificates are issued only for full shares and may be redeposited
in the account at any time. There is no charge to the investor for issuance of a
certificate. Whenever a  shareholder-instituted transaction takes  place in  the
Shareholder Investment Account, the shareholder will be mailed a confirmation of
the transaction from the Fund or from DWR or other selected broker-dealer.
 
    AUTOMATIC  INVESTMENT  OF DIVIDENDS  AND DISTRIBUTIONS.    As stated  in the
Prospectus,  all   income  dividends   and  capital   gains  distributions   are
automatically  paid in full and fractional shares of the applicable Class of the
Fund, unless the shareholder requests that  they be paid in cash. Each  purchase
of  shares of  the Fund is  made upon the  condition that the  Transfer Agent is
thereby automatically  appointed  as  agent  of  the  investor  to  receive  all
dividends  and capital gains distributions on shares owned by the investor. Such
dividends and distributions will be paid, at  the net asset value per share,  in
shares  of the Fund (or in cash if  the shareholder so requests) as of the close
of business on the  monthly payment date,  as stated in  the Prospectus. At  any
time  an investor may request the Transfer Agent, in writing, to have subsequent
dividends and/or capital gains distributions paid  to him or her in cash  rather
than  shares. To assure sufficient  time to process the  change, such request be
received by the Transfer Agent at least five business days prior to the  payment
date  of the  dividend or the  record date of  the distribution. In  the case of
recently purchased  shares for  which registration  instructions have  not  been
received  on the payment  or record date, cash  payments will be  made to DWR or
other selected broker-dealer, and will be forwarded to the shareholder, upon the
receipt of proper instructions.
 
    TARGETED  DIVIDENDS.-SM-    In  states  where  it  is  legally  permissible,
shareholders  may also have all income dividends and capital gains distributions
automatically invested in shares  of any Class of  an open-end Dean Witter  Fund
other  than Dean Witter U.S. Government Securities  Trust or in another Class of
Dean Witter U.S. Government  Securities Trust. Such investment  will be made  as
described  above for automatic  investment in shares of  the applicable Class of
the Fund, at the net asset value per  share of the selected Dean Witter Fund  as
of the close of business on the payment date of the dividend or distribution and
will  begin to earn dividends, if any, in the selected Dean Witter Fund the next
business day. To  participate in  the Targeted  Dividends program,  shareholders
should  contact their DWR  or other selected  broker-dealer account executive or
the Transfer  Agent.  Shareholders of  the  Fund  must be  shareholders  of  the
selected  Class of  the Dean  Witter Fund  targeted to  receive investments from
dividends at  the time  they  enter the  Targeted Dividends  program.  Investors
should  review the prospectus  of the targeted Dean  Witter Fund before entering
the program.
 
    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  Dean Witter money  market fund,  on a semi-monthly,
 
                                       23
<PAGE>
monthly or quarterly basis,  to the Transfer Agent  for investment in shares  of
the Fund. Shares purchased through EasyInvest will be added to the shareholder's
existing  account at the  net asset value  calculated the same  business day the
transfer of  funds is  effected.  For further  information  or to  subscribe  to
EasyInvest,   shareholders   should  contact   their   DWR  or   other  selected
broker-dealer account executive or the Transfer Agent.
 
    INVESTMENT OF DIVIDENDS OR DISTRIBUTIONS RECEIVED IN CASH.  As discussed  in
the  Prospectus,  any shareholder  who receives  a  cash payment  representing a
dividend or capital gains distribution may invest such dividend or  distribution
at  net  asset value,  without  the imposition  of  a CDSC  upon  redemption, by
returning the check  or the proceeds  to the Transfer  Agent within thirty  days
after the payment date. If the shareholder returns the proceeds of a dividend or
distribution,  such funds must  be accompanied by  a signed statement indicating
that the proceeds  constitute a dividend  or distribution to  be invested.  Such
investment  will be made at the net  asset value per share next determined after
receipt of the check or proceeds by the Transfer Agent.
 
    SYSTEMATIC WITHDRAWAL PLAN.   As discussed in  the Prospectus, 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  then  $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"  in  the  Prospectus).
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.
 
    The  Transfer Agent acts  as agent for  the shareholder in  tendering to the
Fund for redemption sufficient full and fractional shares to provide the  amount
of  the periodic  withdrawal payment designated  in the  application. The shares
will be  redeemed at  their net  asset value  determined, at  the  shareholder's
option, on the tenth or twenty-fifth day (or next following business day) of the
relevant  month or quarter and normally a  check for the proceeds will be mailed
by the  Transfer Agent,  or amounts  credited to  a shareholder's  DWR or  other
selected  broker-dealer brokerage account,  within five business  days after the
date of redemption. The  Withdrawal Plan may  be terminated at  any time by  the
Fund.
 
    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.  Although the
shareholder may  make  additional  investments  of  $2,500  or  more  under  the
Withdrawal  Plan, withdrawals made currently with purchases of additional shares
may be inadvisable because of sales charges which may be applicable to purchases
or redemptions of shares (see "Purchase of Fund Shares").
    
 
    Any shareholder who wishes to have  payments under the Withdrawal Plan  made
to  a third party or sent to an address other than the one listed on the account
must send complete written instructions to  the Transfer Agent to enroll in  the
Withdrawal  Plan.  The  shareholder's  signature on  such  instructions  must be
guaranteed  by  an   eligible  guarantor  acceptable   to  the  Transfer   Agent
(shareholders  should  contact  the Transfer  Agent  for a  determination  as to
whether a particular institution is  such an eligible guarantor). A  shareholder
may,  at any time, change the amount and interval of withdrawal payments through
his or her Account Executive or  by written notification to the Transfer  Agent.
In  addition, the  party and/or the  address to  which checks are  mailed may be
changed by written notification to the Transfer Agent, with signature guarantees
required in the manner described above.  The shareholder may also terminate  the
Withdrawal  Plan at  any time by  written notice  to the Transfer  Agent. In the
event  of  such  termination,  the  account  will  be  continued  as  a  regular
shareholder  investment account. The shareholder may  also redeem all or part of
the  shares  held  in  the   Withdrawal  Plan  account  (see  "Redemptions   and
Repurchases" in the Prospectus) at any time.
 
                                       24
<PAGE>
    DIRECT  INVESTMENTS THROUGH TRANSFER AGENT.  As discussed in the Prospectus,
a shareholder may make additional investments in Fund shares at any time through
the Shareholder Investment Account  by sending a check  in any amount, not  less
than  $100, payable to Dean Witter U.S. Government Securities Trust, directly to
the Fund's Transfer Agent. In the case of Class A shares, after deduction of any
applicable sales charge,  the balance will  be applied to  the purchase of  Fund
shares,  and, in the case of shares of the other Classes, the entire amount will
be applied to the purchase of Fund shares, at the net asset value per share next
computed after receipt of the check  or purchase payment by the Transfer  Agent.
The shares so purchased will be credited to the investor's account.
 
EXCHANGE PRIVILEGE
 
    As discussed in the Prospectus, the Fund makes available to its shareholders
an  Exchange Privilege whereby shareholders of each  Class of shares of the Fund
may exchange their shares for  shares of the same Class  of shares of any  other
Dean  Witter Multi-Class Fund without the imposition of any exchange fee. Shares
may also be exchanged for shares of the following Funds: Dean Witter  Short-Term
U.S.  Treasury  Trust, Dean  Witter Limited  Term  Municipal Trust,  Dean Witter
Short-Term Bond Fund, Dean Witter Intermediate Term U.S. Treasury Trust and five
Dean Witter Funds  which are money  market funds (the  foregoing nine funds  are
hereinafter  referred to as  the "Exchange Funds").  Class A shares  may also be
exchanged for shares of Dean Witter Multi-State Municipal Series Trust and  Dean
Witter Hawaii Municipal Trust, which are Dean Witter Funds sold with a front-end
sales  charge ("FSC Funds"). Class B shares  may also be exchanged for shares of
Dean Witter  Global  Short-Term  Income  Fund  Inc.,  Dean  Witter  High  Income
Securities and Dean Witter National Municipal Trust, which are Dean Witter Funds
offered  with a CDSC ("CDSC  Funds"). 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 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.
 
    Any  new account  established through the  Exchange Privilege  will have the
same registration and cash dividend or dividend reinvestment plan as the present
account,  unless  the  Transfer  Agent  receives  written  notification  to  the
contrary.  For  telephone  exchanges,  the exact  registration  of  the existing
account and the account number must be provided.
 
    Any shares  held  in  certificate  form cannot  be  exchanged  but  must  be
forwarded  to the  Transfer Agent and  deposited into  the shareholder's account
before being eligible for exchange.  (Certificates mailed in for deposit  should
not be endorsed.)
 
   
    As  described below,  and in the  Prospectus under the  caption "Purchase of
Fund Shares," a CDSC may be imposed upon a redemption, depending on a number  of
factors,  including the number of years from the time of purchase until the time
of redemption  or exchange  ("holding period").  When shares  of a  Dean  Witter
Multi-Class  Fund or any CDSC Fund are exchanged for shares of an Exchange Fund,
the exchange is executed at no charge to the shareholder, without the imposition
of the  CDSC  at the  time  of  the exchange.  During  the period  of  time  the
shareholder  remains in the Exchange  Fund (calculated from the  last day of the
month in which the  Exchange Fund shares were  acquired), the holding period  or
"year  since purchase payment made"  is frozen. When shares  are redeemed out of
the Exchange Fund, they will be subject to a CDSC which would be based upon  the
period  of time the shareholder held shares in a Dean Witter Multi-Class Fund or
in a CDSC Fund. However, 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. Shareholders  acquiring
shares  of an  Exchange Fund  pursuant to  this exchange  privilege may exchange
those shares back into a  Dean Witter Multi-Class Fund or  a CDSC Fund from  the
Exchange  Fund, with no CDSC being imposed  on such exchange. The holding period
previously frozen when shares  were first exchanged for  shares of the  Exchange
Fund  resumes on  the last day  of the  month in which  shares of  a Dean Witter
Multi-Class Fund or of a CDSC Fund  are reacquired. A CDSC is imposed only  upon
an  ultimate redemption, based upon the time (calculated as described above) the
    
share-
 
                                       25
<PAGE>
   
holder was invested in a Dean Witter Multi-Class Fund or in a CDSC Fund. 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 a FSC Fund.
    
 
   
    When  shares initially purchased in  a Dean Witter Multi-Class  Fund or in a
CDSC Fund are exchanged for shares of a Dean Witter Multi-Class Fund, shares  of
a  CDSC Fund, shares of  a FSC Fund or  shares of an Exchange  Fund, the date of
purchase of the shares of the fund exchanged into, for purposes of the CDSC upon
redemption, will  be  the last  day  of the  month  in which  the  shares  being
exchanged were originally purchased. In allocating the purchase payments between
funds  for purposes  of the  CDSC, the amount  which represents  the current net
asset value of shares at the time of the exchange which were (i) purchased  more
than  one, three or six years (depending  on the CDSC schedule applicable to the
shares) prior to the exchange, (ii) originally acquired through reinvestment  of
dividends  or distributions  and (iii)  acquired in  exchange for  shares of FSC
Funds, or for shares of  other Dean Witter Funds for  which shares of FSC  Funds
have  been exchanged (all  such shares called "Free  Shares"), will be exchanged
first. After an  exchange, all dividends  earned on shares  in an Exchange  Fund
will  be considered Free  Shares. If the  exchanged amount exceeds  the value of
such Free Shares, an  exchange is made, on  a block-by-block basis, of  non-Free
Shares held for the longest period of time (except that, with respect to Class B
shares,  if shares held for  identical periods of time  but subject to different
CDSC schedules are held  in the same Exchange  Privilege account, the shares  of
that  block that are subject to a lower CDSC rate will be exchanged prior to the
shares of that block that  are subject to a higher  CDSC rate). Shares equal  to
any  appreciation in the value  of non-Free Shares exchanged  will be treated as
Free Shares, and the amount of the purchase payments for the non-Free Shares  of
the fund exchanged into will be equal to the lesser of (a) the purchase payments
for, or (b) the current net asset value of, the exchanged non-Free Shares. If an
exchange  between funds would  result in exchange  of only part  of a particular
block of non-Free Shares, then shares equal to any appreciation in the value  of
the  block (up to the amount of the exchange) will be treated as Free Shares and
exchanged first, and the purchase payment for that block will be allocated on  a
pro  rata basis between the non-Free Shares of that block to be retained and the
non-Free Shares to be  exchanged. The prorated amount  of such purchase  payment
attributable to the retained non-Free Shares will remain as the purchase payment
for  such shares, and the amount of  purchase payment for the exchanged non-Free
Shares will be equal to  the lesser of (a) the  prorated amount of the  purchase
payment  for, or (b)  the current net  asset value of,  those exchanged non-Free
Shares. Based upon the procedures described in the Prospectus under the  caption
"Purchase of Fund Shares," any applicable CDSC will be imposed upon the ultimate
redemption  of shares of any  fund, regardless of the  number of exchanges since
those shares were originally purchased.
    
 
    With respect to  the redemption  or repurchase of  shares of  the Fund,  the
application  of proceeds to the purchase of new  shares in the Fund or any other
of the  funds and  the general  administration of  the Exchange  Privilege,  the
Transfer  Agent  acts as  agent for  the Distributor  and for  the shareholder's
selected broker-dealer,  if  any, in  the  performance of  such  functions.  The
Transfer Agent shall be liable for its own negligence and not for the default or
negligence of its correspondents or for losses in transit. The Fund shall not be
liable  for any default or negligence of  the Transfer Agent, the Distributor or
any selected broker-dealer.
 
    The Distributor and any selected broker-dealer have authorized and appointed
the Transfer Agent to act as their  agent in connection with the application  of
proceeds of any redemption of Fund shares to the purchase of shares of any other
fund  and the general administration of the Exchange Privilege. No commission or
discounts will be paid to the Distributor or any selected broker-dealer for  any
transactions pursuant to this Exchange Privilege.
 
    Exchanges  are subject to  the minimum investment  requirement and any other
conditions imposed  by  each  fund.  (The minimum  initial  investment  for  the
Exchange  Privilege account of each Class is $5,000 for Dean Witter Liquid Asset
Fund Inc.,  Dean Witter  Tax-Free  Daily Income  Trust, Dean  Witter  California
Tax-Free  Daily Income  Trust and  Dean Witter  New York  Municipal Money Market
Trust, al-
though those funds may,  at their discretion, accept  initial investments of  as
low as $1,000. The minimum
 
                                       26
<PAGE>
initial  investment for the Exchange Privilege  account of each Class is $10,000
for Dean Witter Short-Term U.S. Treasury  Trust, although that fund may, at  its
discretion,  may  accept initial  purchases  of as  low  as $5,000.  The minimum
initial investment for the  Exchange Privilege account of  each Class is  $5,000
for  Dean  Witter Special  Value Fund.  The minimum  initial investment  for the
Exchange Privilege account  of each  Class of all  other Dean  Witter Funds  for
which  the Exchange  Privilege is  available is  $1,000.) Upon  exchange into an
Exchange Fund,  the shares  of that  fund will  be held  in a  special  Exchange
Privilege  Account  separately  from  accounts of  those  shareholders  who have
acquired their shares  directly from that  fund. As a  result, certain  services
normally  available to shareholders of those  funds, including the check writing
feature, will not be available for funds held in that account.
 
    The Fund and each  of the other  Dean Witter Funds may  limit the number  of
times  this  Exchange  Privilege  may  be exercised  by  any  investor  within a
specified period of  time. Also,  the Exchange  Privilege may  be terminated  or
revised  at any time by the  Fund and/or any of the  Dean Witter Funds for which
shares of the Fund have been exchanged,  upon such notice as may be required  by
applicable  regulatory agencies (presently sixty  days' prior written notice for
termination or  material  revision), provided  that  six months'  prior  written
notice  of termination will be  given to the shareholders  who hold shares of an
Exchange Fund pursuant to the Exchange Privilege, and provided further that  the
Exchange  Privilege may  be terminated or  materially revised  without notice at
times (a) when the New  York Stock Exchange is  closed for other than  customary
weekends and holidays, (b) when trading on that Exchange is restricted, (c) when
an  emergency exists  as a result  of which  disposal by the  Fund of securities
owned by it is  not reasonably practicable or  it is not reasonably  practicable
for  the Fund fairly  to determine the value  of its net  assets, (d) during any
other period when  the Securities and  Exchange Commission by  order so  permits
(provided  that applicable rules and regulations  of the Securities and Exchange
Commission shall govern as  to whether the conditions  prescribed in (b) or  (c)
exist)  or (e)  if the  Fund would  be unable  to invest  amounts effectively in
accordance with its investment objective, policies and restrictions.
 
    Shareholders should  contact  their  DWR  or  other  selected  broker-dealer
account  executive  or  the Transfer  Agent  for further  information  about the
Exchange Privilege.
 
REDEMPTIONS AND REPURCHASES
- --------------------------------------------------------------------------------
 
    REDEMPTION.  As stated in the Prospectus,  shares of each Class of the  Fund
can  be redeemed  for cash at  any time  at the net  asset value  per share next
determined; however, such redemption  proceeds may be reduced  by the amount  of
any  applicable CDSC. 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. The share certificate, or an accompanying
stock power, and the request for  redemption, must be signed by the  shareholder
or  shareholders  exactly  as  the  shares  are  registered.  Each  request  for
redemption, whether or not accompanied by  a share certificate, must be sent  to
the Fund's Transfer Agent, which will redeem the shares at their net asset value
next  computed  (see  "Purchase of  Fund  Shares"  in the  Prospectus)  after it
receives the request,  and certificate, if  any, in good  order. Any  redemption
request  received after such computation will be redeemed at the next determined
net asset value. The term "good order" means that the share certificate, if any,
and request for redemption are properly signed, accompanied by any documentation
required by the Transfer Agent, and  bear signature guarantees when required  by
the  Fund or the  Transfer Agent. If  redemption is requested  by a corporation,
partnership, trust or  fiduciary, the  Transfer Agent may  require that  written
evidence  of authority acceptable to the Transfer Agent be submitted before such
request is accepted.
 
    Whether certificates are  held by the  shareholder or shares  are held in  a
shareholder's  account, if the proceeds are to  be paid to any person other than
the record owner, or if the proceeds are to be paid to a corporation (other than
the Distributor or a selected broker-dealer for the account of the shareholder),
partnership, trust or fiduciary, or sent to the shareholder at an address  other
than  the  registered  address, signatures  must  be guaranteed  by  an eligible
guarantor acceptable to the Transfer Agent (shareholders
 
                                       27
<PAGE>
should contact the Transfer Agent for a determination as to whether a particular
institution is such an eligible guarantor).  A stock power may be obtained  from
any  dealer  or commercial  bank. The  Fund may  change the  signature guarantee
requirements from time  to time  upon notice to  shareholders, which  may be  by
means of a supplement to the prospectus or a new prospectus.
 
    REPURCHASE.     As  stated  in  the   Prospectus,  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 after
such purchase order is received by  DWR or other selected broker-dealer  reduced
by any applicable CDSC.
 
    PAYMENT FOR SHARES REDEEMED OR REPURCHASED.  As discussed in the Prospectus,
payment  for shares of any Class 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. The  term "good order" means
that the share  certificate, if  any, and  request for  redemption are  properly
signed,  accompanied by  any documentation required  by the  Transfer Agent, and
bear signature guarantees when required by the Fund or the Transfer Agent.  Such
payment  may be postponed or the right of redemption suspended at times (a) when
the New York  Stock Exchange  is closed for  other than  customary weekends  and
holidays, (b) when trading on that Exchange is restricted, (c) when an emergency
exists  as a result of which  disposal by the Fund of  securities owned by it is
not reasonably practicable  or it  is not  reasonably practicable  for the  Fund
fairly  to determine the value of its net assets, or (d) during any other period
when the Securities and Exchange Commission  by order so permits; provided  that
applicable rules and regulations of the Securities and Exchange Commission shall
govern  as to  whether the  conditions prescribed  in (b)  or (c)  exist. If the
shares to  be  redeemed have  recently  been  purchased by  check  (including  a
certified  or  bank  cashier's check),  payment  of 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  account  executive
regarding restrictions on redemption of shares of the Fund pledged in the margin
accounts.
 
   
    TRANSFERS  OF SHARES.  In the event a shareholder requests a transfer of any
shares to a  new registration,  such shares  will be  transferred without  sales
charge  at the time of  transfer. With regard to the  status of shares which are
either subject to the CDSC or free of such charge (and with regard to the length
of time shares  subject to the  charge have been  held), any transfer  involving
less than all of the shares in an account will be made on a pro rata basis (that
is,  by transferring shares  in the same proportion  that the transferred shares
bear to the total shares in the account immediately prior to the transfer).  The
transferred shares will continue to be subject to any applicable CDSC as if they
had not been so transferred.
    
 
    REINSTATEMENT  PRIVILEGE.  As discussed in the Prospectus, 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
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  at the net
asset value next  determined after  a reinstatement request,  together with  the
proceeds, is received by the Transfer Agent.
 
    Exercise  of the reinstatement privilege will  not affect the federal income
tax treatment of any  gain or loss realized  upon the redemption or  repurchase,
except that if the redemption or repurchase resulted in a loss and reinstatement
is  made in shares of the Fund, some or all of the loss, depending on the amount
reinstated, will not be allowed as  a deduction for federal income tax  purposes
but  will  be applied  to  adjust the  cost basis  of  the shares  acquired upon
reinstatement.
 
                                       28
<PAGE>
DIVIDENDS, DISTRIBUTIONS AND TAXES
- --------------------------------------------------------------------------------
 
    As discussed in the Prospectus, the Fund will determine either to distribute
or to retain  all or part  of any net  long-term capital gains  in any year  for
reinvestment.  If any such gains are retained,  the Fund will pay federal income
tax thereon and  will notify  shareholders that,  following an  election by  the
Fund,  the shareholders will be required  to include such undistributed gains in
determining their taxable income and  may claim their share  of the tax paid  by
the Fund as a credit against their individual federal income tax.
 
    Because  the Fund intends to distribute all of its net investment income and
capital gains to shareholders and otherwise  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.
Shareholders  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 or  short-term capital gains, are taxable to
the shareholder  as  ordinary  income  regardless  of  whether  the  shareholder
receives  such payments 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 received  by the shareholder  in the prior
year.
 
    Gains or losses on sales of securities by the Fund will be long-term capital
gains or losses  if the  securities have  been held by  the Fund  for more  than
twelve  months. Gains or losses on the sale of securities held for twelve months
or less will be short-term gains or losses.
 
    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 dividends received deduction.
 
    Net  income,   for  dividend   purposes,  includes   accrued  interest   and
amortization  of original issue discount  and market discounts where applicable,
less the expenses of the Fund.  Net income will be calculated immediately  prior
to the determination of net asset value per share of the Fund.
 
    Under  current federal law,  the Fund will receive  net investment income in
the form of interest by virtue of  holding Treasury bills, notes and bonds,  and
will  recognize  income attributable  to it  from  holding zero  coupon Treasury
securities. 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
payment in cash on the security during  the year. As an investment company,  the
Fund  must pay  out substantially  all of its  net investment  income each year.
Accordingly, the  Fund,  to  the  extent it  invests  in  zero  coupon  Treasury
securities,  may be required to  pay out as an  income distribution each year an
amount which is greater than the total  amount of cash receipts of interest  the
Fund  actually received. Such distributions will be made from the available cash
of the  Fund  or by  liquidation  of portfolio  securities  if necessary.  If  a
distribution  of cash necessitates the  liquidation of portfolio securities, the
Investment Manager will select which securities to sell. The Fund may realize  a
gain  or loss from such sales. In the  event the Fund realizes net capital gains
from such  transactions, its  shareholders  may receive  a larger  capital  gain
distribution, if any, than they would in the absence of such transactions.
 
    Any dividend or capital gains distribution received by a shareholder from an
investment  company will have the effect of  reducing the net asset value of the
shareholder's stock  in that  company by  the exact  amount of  the dividend  or
capital   gains  distribution.  Furthermore,  capital  gains  distributions  and
dividends are subject to  federal income taxes.  If the net  asset value of  the
shares  should be reduced below a shareholder's  cost as a result of the payment
of dividends  or the  distribution  of realized  long-term capital  gains,  such
payment  or  distribution  would  be  in  part  a  return  of  the shareholder's
investment to the  extent of such  reduction below the  shareholder's cost,  but
nonetheless would be fully taxable at
 
                                       29
<PAGE>
either  ordinary or capital  gain rates. Therefore,  an investor should consider
the  tax  implications  of  purchasing  Fund  shares  immediately  prior  to   a
distribution record date.
 
    Shareholders  are urged to consult their attorneys or tax advisers regarding
specific questions as to federal, state or local taxes.
 
PERFORMANCE INFORMATION
- --------------------------------------------------------------------------------
 
   
    As discussed in the  Prospectus, 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.  Yield is  calculated for  any 30-day period  as follows:  the amount of
interest income  for each  security in  the Fund's  portfolio is  determined  in
accordance  with regulatory  requirements; the  total for  the entire portfolio,
adjusted by the  gain or  loss on paydowns  during the  period, constitutes  the
Fund's  gross  income for  the period.  Expenses accrued  during the  period are
subtracted to arrive  at "net investment  income" of each  Class. The  resulting
amount  is divided by the product of the maximum offering price per share on the
last day  of the  period  multiplied by  the average  number  of shares  of  the
applicable  Class outstanding during the period that were entitled to dividends.
This amount is added to  1 and raised to the  sixth power. 1 is then  subtracted
from  the  result  and  the difference  is  multiplied  by 2  to  arrive  at the
annualized yield. For  the 30-day  period ended  December 31,  1996, the  Fund's
yield, calculated pursuant to the formula described above, was 6.11%. This yield
is  for Class B only; there were no  other Classes of shares outstanding on such
date.
    
 
    The Fund's "average annual total return" represents an annualization of  the
Fund's  total return  over a  particular period and  is computed  by finding the
annual percentage rate  which will result  in the ending  redeemable value of  a
hypothetical  $1,000 investment made at the beginning of a one, five or ten year
period, or  for  the  period  from  the  date  of  commencement  of  the  Fund's
operations, if shorter than any of the foregoing. The ending redeemable value is
reduced by any CDSC at the end of the one, five or ten year or other period. For
the  purpose  of  this  calculation,  it  is  assumed  that  all  dividends  and
distributions are reinvested. The formula for computing the average annual total
return involves a percentage obtained by dividing the ending redeemable value by
the amount of the initial investment, taking  a root of the quotient (where  the
root  is equivalent to the number of years in the period) and subtracting 1 from
the result. The  average annual total  returns of  the Fund for  the year  ended
December  31, 1996, for the  five years ended December 31,  1996 and for the ten
years ended December 31, 1996 were -1.69%, 5.35% and 6.97%, respectively.  These
returns  are for Class B only; there were no other Classes of shares outstanding
on such date.
 
   
    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,
year-by-year or other types  of total return figures.  Such calculations may  or
may not reflect the imposition of the maximum front-end sales charge for Class A
or  the  deduction of  the  CDSC for  each  of Class  B  and Class  C  which, if
reflected, would reduce the performance quoted. For example, the average  annual
total  return of the  Fund may be  calculated in the  manner described above but
without deduction for any  applicable sales charge.  Based on this  calculation,
the  average annual total  returns of the  Fund for the  year ended December 31,
1996, for the five  years ended December  31, 1996 and for  the ten years  ended
December  31, 1996 were 3.16%, 5.65%  and 6.97%, respectively. These returns are
for Class B  only; there were  no other  Classes of shares  outstanding on  such
date.
    
 
   
    In  addition, the Fund may compute its aggregate total return for each Class
for specified periods by  determining the aggregate  percentage rate which  will
result  in the  ending value  of a  hypothetical $1,000  investment made  at the
beginning of the period. For the purpose of this calculation, it is assumed that
all dividends  and  distributions  are reinvested.  The  formula  for  computing
aggregate  total return  involves a percentage  obtained by  dividing the ending
value (without  the  reduction for  any  sales  charge) by  the  initial  $1,000
investment   and  subtracting  1  from  the   result.  Based  on  the  foregoing
calculation, the Fund's total  return for the year  ended December 31, 1996  was
3.16%,  the total return for the five  years ended December 31, 1996 was 31.65%,
and  the   total  return   for   the  ten   years   ended  December   31,   1996
    
 
                                       30
<PAGE>
was  96.14%. These returns are for Class B  only; there were no other Classes of
shares outstanding on such date.
 
   
    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 by adding 1 to
the  Fund's aggregate total return  to date (expressed as  a decimal and without
taking into  account the  effect  of any  applicable  CDSC) and  multiplying  by
$9,575,  $47,250 and  $97,250 in  the case of  Class A  (investments of $10,000,
$50,000 and  $100,000 adjusted  for the  initial sales  charge) or  by  $10,000,
$50,000 and $100,000 in the case of each of Class B, Class C and Class D, as the
case  may  be. Investments  of  $10,000, $50,000  and  $100,000 in  the  Fund at
inception (June 29, 1984)  would have grown to  $26,827, $134,135 and  $268,270,
respectively,  at December 31, 1996. This information is for Class B only; there
were no other Classes of shares outstanding on such date.
    
 
    The Fund from time  to time may also  advertise its performance relative  to
certain performance rankings and indexes compiled by independent organizations.
 
DESCRIPTION OF SHARES OF THE FUND
- --------------------------------------------------------------------------------
 
    The shareholders of the Fund are entitled to a full vote for each full share
held.  All of the  Trustees have been  elected by the  shareholders of the Fund,
most recently at a Special Meeting of Shareholders held on May 21, 1997. On that
date, Wayne E. Hedien was also elected as  a Trustee of the Fund, with his  term
to  commence on September 1, 1997. The  Fund is authorized to issue an unlimited
number of shares of beneficial interest. The Trustees themselves have the  power
to  alter the number and the terms of office of the Trustees (as provided for in
the Declaration of Trust), and they may at any time lengthen their own terms  or
make  their  terms  of  unlimited duration  and  appoint  their  own successors,
provided that always at least a majority of the Trustees has been elected by the
shareholders of  the  Fund. Under  certain  circumstances the  Trustees  may  be
removed  by action of the  Trustees. The shareholders also  have the right under
certain circumstances to remove the Trustees. The voting rights of  shareholders
are not cumulative, so that holders of more than 50 percent of the shares voting
can, if they choose, elect all Trustees being selected, while the holders of the
remaining shares would be unable to elect any Trustees.
 
    The  Declaration of Trust permits the  Trustees to authorize the creation of
additional series  of  shares  (the  proceeds of  which  would  be  invested  in
separate,  independently managed  portfolios) and  additional classes  of shares
within any  series (which  would be  used  to distinguish  among the  rights  of
different categories of shareholders, as might be required by future regulations
or  other unforeseen circumstances).  The Trustees have  not authorized any such
additional series  or  classes  of  shares  other  than  as  set  forth  in  the
Prospectus.
 
    The Declaration of Trust further provides that no Trustee, officer, employee
or  agent of  the Fund is  liable to the  Fund or  to a shareholder,  nor is any
Trustee, officer, employee or  agent liable to any  third persons in  connection
with the affairs of the Fund, except as such liability may arise from his/her or
its  own bad faith, willful misfeasance, gross negligence, or reckless disregard
of his duties. It also provides that all third persons shall look solely to  the
Fund  property for satisfaction of claims arising in connection with the affairs
of the Fund. With the exceptions stated, the Declaration of Trust provides  that
a  Trustee, officer, employee or agent is entitled to be indemnified against all
liability in connection with the affairs of the Fund.
 
    The Fund is authorized to issue an unlimited number of shares of  beneficial
interest.  The Fund shall be of unlimited  duration subject to the provisions in
the Declaration of Trust concerning termination by action of the shareholders.
 
                                       31
<PAGE>
CUSTODIAN AND TRANSFER AGENT
- --------------------------------------------------------------------------------
 
    The Bank of New York, 90 Washington Street, New York, New York 10286 is  the
Custodian  of  the Fund's  assets.  Any of  the  Fund's cash  balances  with the
Custodian in excess of  $100,000 are unprotected  by federal deposit  insurance.
Such balances may, at times, be substantial.
 
    Dean  Witter Trust Company,  Harborside Financial Center,  Plaza Two, Jersey
City, New Jersey 07311 is the Transfer  Agent of the Fund's shares and  Dividend
Disbursing  Agent for payment of dividends  and distributions on Fund shares and
Agent for shareholders  under various  investment plans  described herein.  Dean
Witter  Trust  Company is  an affiliate  of Dean  Witter InterCapital  Inc., the
Fund's Investment  Manager, and  of Dean  Witter Distributors  Inc., the  Fund's
Distributor.  As Transfer Agent and Dividend Disbursing Agent, Dean Witter Trust
Company's responsibilities include maintaining shareholder accounts,  disbursing
cash  dividends  and  reinvesting  dividends,  processing  account  registration
changes, handling purchase and redemption transactions, mailing prospectuses and
reports,  mailing   and  tabulating   proxies,  processing   share   certificate
transactions,  and maintaining shareholder records and lists. For these services
Dean Witter Trust Company receives a per shareholder account fee from the Fund.
 
INDEPENDENT ACCOUNTANTS
- --------------------------------------------------------------------------------
 
    Price Waterhouse LLP serves as the independent accountants of the Fund.  The
independent  accountants  are  responsible  for  auditing  the  annual financial
statements of the Fund.
 
REPORTS TO SHAREHOLDERS
- --------------------------------------------------------------------------------
 
    The Fund will send to shareholders, at least semi-annually, reports  showing
the  Fund's  portfolio  and  other  information.  An  annual  report, containing
financial statements  audited  by  independent  accountants,  will  be  sent  to
shareholders each year.
 
    The  Fund's fiscal year ends on December 31. The financial statements of the
Fund must  be audited  at least  once a  year by  independent accountants  whose
selection is made annually by the Fund's Board of Trustees.
 
LEGAL COUNSEL
- --------------------------------------------------------------------------------
 
    Barry  Fink, Esq., who is  an officer and General  Counsel of the Investment
Manager, is an officer and General Counsel of the Fund.
 
EXPERTS
- --------------------------------------------------------------------------------
 
    The annual financial statements of the Fund for the year ended December  31,
1996,  which  are  included  in this  Statement  of  Additional  Information and
incorporated  by  reference  in  the  Prospectus,  have  been  so  included  and
incorporated  in reliance  on the  report of  Price Waterhouse  LLP, independent
accountants, given on  the authority  of said firm  as experts  in auditing  and
accounting.
 
REGISTRATION STATEMENT
- --------------------------------------------------------------------------------
 
    This  Statement of Additional Information and  the Prospectus do not contain
all of the  information set  forth in the  Registration Statement  the Fund  has
filed  with the  Securities and  Exchange Commission.  The complete Registration
Statement may  be obtained  from  the Securities  and Exchange  Commission  upon
payment of the fee prescribed by the rules and regulations of the Commission.
 
                                       32
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
REPORT OF INDEPENDENT ACCOUNTANTS
 
TO THE SHAREHOLDERS AND TRUSTEES
OF DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
 
In our opinion, the accompanying statement of assets and liabilities, including
the portfolio of investments, and the related statements of operations and of
changes in net assets and the financial highlights present fairly, in all
material respects, the financial position of Dean Witter U.S. Government
Securities Trust (the "Fund") at December 31, 1996, the results of its
operations for the year then ended, the changes in its net assets for each of
the two years in the period then ended and the financial highlights for each of
the ten years in the period then ended, in conformity with generally accepted
accounting principles. These financial statements and financial highlights
(hereafter referred to as "financial statements") are the responsibility of the
Fund's management; our responsibility is to express an opinion on these
financial statements based on our audits. We conducted our audits of these
financial statements in accordance with generally accepted auditing standards
which require that we plan and perform the audit to obtain reasonable assurance
about whether the financial statements are free of material misstatement. An
audit includes examining, on a test basis, evidence supporting the amounts and
disclosures in the financial statements, assessing the accounting principles
used and significant estimates made by management, and evaluating the overall
financial statement presentation. We believe that our audits, which included
confirmation of securities at December 31, 1996 by correspondence with the
custodian and a broker, provide a reasonable basis for the opinion expressed
above.
 
PRICE WATERHOUSE LLP
1177 AVENUE OF THE AMERICAS
NEW YORK, NEW YORK 10036
FEBRUARY 18, 1997
 
                                       33
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
PORTFOLIO OF INVESTMENTS DECEMBER 31, 1996
 
<TABLE>
<CAPTION>
   PRINCIPAL                                  DESCRIPTION
   AMOUNT IN                                      AND                                   COUPON
   THOUSANDS                                 MATURITY DATE                               RATE          VALUE
- ------------------------------------------------------------------------------------------------------------------
<C>                <S>                                                                 <C>        <C>
                   MORTGAGE-BACKED SECURITIES (80.5%)
                   Government National Mortgage Assoc. I (79.6%)
$        348,269   10/15/22-02/15/24.................................................        6.50% $    332,053,085
          25,000   (a)...............................................................        7.00       24,437,500
       2,194,356   04/15/17-04/15/26.................................................        7.00    2,144,983,431
       1,098,215   11/15/02-06/15/26.................................................        7.50    1,098,557,782
         372,670   10/15/16-07/15/26.................................................        8.00      380,240,075
         390,028   07/15/06-04/15/25.................................................        8.50      404,044,832
         283,195   10/15/08-08/15/21.................................................        9.00      298,239,454
         199,610   10/15/09-12/15/20.................................................        9.50      215,641,679
         214,924   11/15/09-11/15/20.................................................       10.00      235,543,142
             588   04/15/10-06/15/15.................................................       12.50          676,881
                                                                                                  ----------------
                                                                                                     5,134,417,861
                                                                                                  ----------------
 
                   Government National Mortgage Assoc. II (0.7%)
          49,127   01/20/24-02/20/24.................................................        6.50       46,624,166
                                                                                                  ----------------
 
                   Government National Mortgage Assoc. GPM I (0.2%)
           9,269   06/15/13-09/15/15.................................................       12.25       10,794,963
                                                                                                  ----------------
 
                   TOTAL MORTGAGE-BACKED SECURITIES
                   (IDENTIFIED COST $5,168,329,453)............................................      5,191,836,990
                                                                                                  ----------------
 
                   U.S. GOVERNMENT OBLIGATIONS (13.4%)
                   U.S. Treasury Notes (4.1%)
          29,000   02/28/97..........................................................        6.875       29,073,370
          42,500   03/31/97..........................................................        6.875       42,660,650
          75,000   04/15/97..........................................................        8.50       75,653,250
          58,000   04/30/97..........................................................        6.875       58,294,640
          55,000   04/15/99..........................................................        7.00       56,235,850
                                                                                                  ----------------
                                                                                                       261,917,760
                                                                                                  ----------------
 
                   U.S. Treasury Coupon Strips (9.3%)
         123,000   02/15/04..........................................................        0.00       78,426,030
         380,000   05/15/04..........................................................        0.00      238,001,600
         385,000   08/15/04..........................................................        0.00      237,129,200
          75,000   11/15/04..........................................................        0.00       45,396,750
                                                                                                  ----------------
                                                                                                       598,953,580
                                                                                                  ----------------
 
                   TOTAL U.S. GOVERNMENT OBLIGATIONS
                   (IDENTIFIED COST $778,502,738)..............................................        860,871,340
                                                                                                  ----------------
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
                                       34
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
PORTFOLIO OF INVESTMENTS DECEMBER 31, 1996, CONTINUED
 
<TABLE>
<CAPTION>
   PRINCIPAL                                  DESCRIPTION
   AMOUNT IN                                      AND                                   COUPON
   THOUSANDS                                 MATURITY DATE                               RATE          VALUE
- ------------------------------------------------------------------------------------------------------------------
<C>                <S>                                                                 <C>        <C>
                   U.S. GOVERNMENT AGENCIES (6.2%)
                   Resolution Funding Corp Zero Coupon Strips
$         33,500   07/15/02..........................................................        0.00% $     23,649,660
          10,049   10/15/02..........................................................        0.00        6,975,614
         109,000   04/15/03..........................................................        0.00       72,932,990
          55,000   07/15/03..........................................................        0.00       36,196,600
          69,000   10/15/03..........................................................        0.00       44,616,090
         123,882   01/15/04..........................................................        0.00       78,748,072
         104,419   04/15/04..........................................................        0.00       65,220,107
          80,000   07/15/04..........................................................        0.00       49,127,200
          40,000   04/15/06..........................................................        0.00       21,746,800
           5,000   10/15/06..........................................................        0.00        2,626,900
                                                                                                  ----------------
 
                   TOTAL U.S. GOVERNMENT AGENCIES
                   (IDENTIFIED COST $365,230,502)..............................................        401,840,033
                                                                                                  ----------------
 
               TOTAL INVESTMENTS
               (IDENTIFIED COST $6,312,062,693) (B).............................  100.1%      6,454,548,363
 
               LIABILITIES IN EXCESS OF CASH AND OTHER ASSETS...................   (0.1)         (5,010,207)
                                                                                  ------   ----------------
 
               NET ASSETS.......................................................  100.0%   $  6,449,538,156
                                                                                  ------   ----------------
                                                                                  ------   ----------------
 
<FN>
- ---------------------
GPM  Graduated Payment Mortgage.
(a)  Securities purchased on a forward commitment basis with an approximate
     principal amount and no definite maturity date; the actual principal
     amount and maturity date will be determined upon settlement.
(b)  The aggregate cost for federal income tax purposes approximates identified
     cost. The aggregate gross unrealized appreciation is $211,958,662 and the
     aggregate gross unrealized depreciation is $69,472,992, resulting in net
     unrealized appreciation of $142,485,670.
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
                                       35
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
FINANCIAL STATEMENTS
 
STATEMENT OF ASSETS AND LIABILITIES
DECEMBER 31, 1996
 
<TABLE>
<S>                                                           <C>
ASSETS:
Investments in securities, at value
  (identified cost $6,312,062,693)..........................  $   6,454,548,363
Cash........................................................            449,209
Receivable for:
    Interest................................................         37,055,157
    Shares of beneficial interest sold......................         13,471,656
Prepaid expenses and other assets...........................            100,149
                                                              -----------------
 
     TOTAL ASSETS...........................................      6,505,624,534
                                                              -----------------
 
LIABILITIES:
Payable for:
    Investments purchased...................................         24,730,035
    Dividends to shareholders...............................         18,555,177
    Shares of beneficial interest repurchased...............          5,216,188
    Plan of distribution fee................................          4,283,834
    Investment management fee...............................          2,404,212
Accrued expenses and other payables.........................            896,932
                                                              -----------------
 
     TOTAL LIABILITIES......................................         56,086,378
                                                              -----------------
 
NET ASSETS:
Paid-in-capital.............................................      7,598,295,399
Net unrealized appreciation.................................        142,485,670
Dividends in excess of net investment income................             (4,722)
Accumulated net realized loss...............................     (1,291,238,191)
                                                              -----------------
 
     NET ASSETS.............................................  $   6,449,538,156
                                                              -----------------
                                                              -----------------
 
NET ASSET VALUE PER SHARE,
  723,414,184 SHARES OUTSTANDING (UNLIMITED SHARES
  AUTHORIZED OF $.01 PAR VALUE).............................
                                                                          $8.92
                                                              -----------------
                                                              -----------------
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
                                       36
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
FINANCIAL STATEMENTS, CONTINUED
 
STATEMENT OF OPERATIONS
FOR THE YEAR ENDED DECEMBER 31, 1996
 
<TABLE>
<S>                                                           <C>
NET INVESTMENT INCOME:
 
INTEREST INCOME.............................................  $    533,679,451
                                                              ----------------
 
EXPENSES
Plan of distribution fee....................................        53,189,389
Investment management fee...................................        29,579,546
Transfer agent fees and expenses............................         4,382,628
Custodian fees..............................................         1,025,583
Shareholder reports and notices.............................           177,325
Professional fees...........................................           107,597
Registration fees...........................................            31,140
Trustees' fees and expenses.................................            22,931
Servicing fees..............................................            19,454
Other.......................................................            68,060
                                                              ----------------
 
     TOTAL EXPENSES.........................................        88,603,653
 
     LESS EXPENSE OFFSET....................................           (20,817)
                                                              ----------------
 
     NET EXPENSES...........................................        88,582,836
                                                              ----------------
 
     NET INVESTMENT INCOME..................................       445,096,615
                                                              ----------------
 
NET REALIZED AND UNREALIZED LOSS:
Net realized loss...........................................       (18,950,945)
Net change in unrealized appreciation.......................      (237,138,336)
                                                              ----------------
 
     NET LOSS...............................................      (256,089,281)
                                                              ----------------
 
NET INCREASE................................................  $    189,007,334
                                                              ----------------
                                                              ----------------
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
                                       37
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
FINANCIAL STATEMENTS, CONTINUED
 
STATEMENT OF CHANGES IN NET ASSETS
 
<TABLE>
<CAPTION>
                                                                                    FOR THE YEAR
                                                                FOR THE YEAR           ENDED
                                                                    ENDED           DECEMBER 31,
                                                              DECEMBER 31, 1996         1995
- --------------------------------------------------------------------------------------------------
<S>                                                           <C>                 <C>
 
INCREASE (DECREASE) IN NET ASSETS:
 
OPERATIONS:
Net investment income.......................................   $    445,096,615   $    522,928,136
Net realized loss...........................................        (18,950,945)       (77,736,417)
Net change in unrealized appreciation/depreciation..........       (237,138,336)       811,733,423
                                                              -----------------   ----------------
 
     NET INCREASE...........................................        189,007,334      1,256,925,142
 
Dividends from net investment income........................       (447,472,130)      (522,076,848)
Net decrease from transactions in shares of beneficial
  interest..................................................     (1,246,903,069)      (990,646,568)
                                                              -----------------   ----------------
 
     NET DECREASE...........................................     (1,505,367,865)      (255,798,274)
 
NET ASSETS:
Beginning of period.........................................      7,954,906,021      8,210,704,295
                                                              -----------------   ----------------
 
     END OF PERIOD
    (INCLUDING DIVIDENDS IN EXCESS OF NET INVESTMENT INCOME
    OF $4,722 AND UNDISTRIBUTED NET INVESTMENT INCOME OF
    $2,370,793, RESPECTIVELY)...............................   $  6,449,538,156   $  7,954,906,021
                                                              -----------------   ----------------
                                                              -----------------   ----------------
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
                                       38
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
NOTES TO FINANCIAL STATEMENTS DECEMBER 31, 1996
 
1. ORGANIZATION AND ACCOUNTING POLICIES
 
Dean Witter U.S. Government Securities Trust (the "Fund") is registered under
the Investment Company Act of 1940, as amended (the "Act"), as a diversified,
open-end management investment company. The Fund's investment objective is high
current income consistent with safety of principal. The Fund seeks to achieve
its objective by investing in obligations issued or guaranteed by the U.S.
Government or its instrumentalities. The Fund was organized as a Massachusetts
business trust on September 29, 1983 and commenced operations on June 29, 1984.
 
The preparation of financial statements in accordance with generally accepted
accounting principles requires management to make estimates and assumptions that
affect the reported amounts and disclosures. Actual results could differ from
those estimates.
 
The following is a summary of significant accounting policies:
 
A. VALUATION OF INVESTMENTS -- (1) all portfolio securities for which
over-the-counter market quotations are readily available are valued at the
latest available bid price prior to the time of valuation; (2) when market
quotations are not readily available, including circumstances under which it is
determined by Dean Witter InterCapital Inc. (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 Trustees
(valuation of debt 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) certain portfolio securities may be valued by an
outside pricing service approved by the Trustees. The pricing service may
utilize a matrix system incorporating security quality, maturity and coupon as
the evaluation model parameters, and/ or research and evaluations by its staff,
including review of broker-dealer market price quotations, if available, in
determining what it believes is the fair valuation of the securities valued by
such pricing service; (4) short-term debt securities having a maturity date of
more than sixty days at time of purchase are valued on a mark-to-market basis
until sixty days prior to maturity and thereafter at amortized cost based on
their value on the 61st day. Short-term securities having a maturity date of
sixty days or less at the time of purchase are valued at amortized cost.
 
B. ACCOUNTING FOR INVESTMENTS -- Security transactions are accounted for on the
trade date (date the order to buy or sell is executed). Realized gains and
losses on security transactions are determined by the identified cost method.
Discounts are accreted over the life of the respective securities. Interest
income is accrued daily.
 
                                       39
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
NOTES TO FINANCIAL STATEMENTS DECEMBER 31, 1996, CONTINUED
 
C. FEDERAL INCOME TAX STATUS -- It is the Fund's policy to comply with the
requirements of the Internal Revenue Code applicable to regulated investment
companies and to distribute all of its taxable income to its shareholders.
Accordingly, no federal income tax provision is required.
 
D. DIVIDENDS AND DISTRIBUTIONS TO SHAREHOLDERS --  The Fund records dividends
and distributions to its shareholders on the record date. The amount of
dividends and distributions from net investment income and net realized capital
gains are determined in accordance with federal income tax regulations which may
differ from generally accepted accounting principles. These "book/tax"
differences are either considered temporary or permanent in nature. To the
extent these differences are permanent in nature, such amounts are reclassified
within the capital accounts based on their federal tax-basis treatment;
temporary differences do not require reclassification. Dividends and
distributions which exceed net investment income and net realized capital gains
for financial reporting purposes but not for tax purposes are reported as
dividends in excess of net investment income or distributions in excess of net
realized capital gains. To the extent they exceed net investment income and net
realized capital gains for tax purposes, they are reported as distributions of
paid-in-capital.
 
2. INVESTMENT MANAGEMENT AGREEMENT
 
Pursuant to an Investment Management Agreement with the Investment Manager, the
Fund pays the Investment Manager a management fee, accrued daily and payable
monthly, by applying the following annual rates to the Fund's net assets
determined at the close of each business day: 0.50% to the portion of daily net
assets not exceeding $1 billion; 0.475% to the portion of daily net assets
exceeding $1 billion but not exceeding $1.5 billion; 0.45% to the portion of
daily net assets exceeding $1.5 billion but not exceeding $2 billion; 0.425% to
the portion of daily net assets exceeding $2 billion but not exceeding $2.5
billion; 0.40% to the portion of daily net assets exceeding $2.5 billion but not
exceeding $5 billion; 0.375% to the portion of daily net assets exceeding $5
billion but not exceeding $7.5 billion; 0.35% to the portion of daily net assets
exceeding $7.5 billion but not exceeding $10 billion; 0.325% to the portion of
daily net assets exceeding $10 billion but not exceeding $12.5 billion; and
0.30% to the portion of daily net assets exceeding $12.5 billion.
 
Under the terms of the Agreement, in addition to managing the Fund's
investments, the Investment Manager maintains certain of the Fund's books and
records and furnishes, at its own expense, office space, facilities, equipment,
clerical, bookkeeping and certain legal services and pays the salaries of
 
                                       40
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
NOTES TO FINANCIAL STATEMENTS DECEMBER 31, 1996, CONTINUED
 
all personnel, including officers of the Fund who are employees of the
Investment Manager. The Investment Manager also bears the cost of telephone
services, heat, light, power and other utilities provided to the Fund.
 
3. PLAN OF DISTRIBUTION
 
Shares of the Fund are distributed by Dean Witter Distributors Inc. (the
"Distributor"), an affiliate of the Investment Manager. The Fund has adopted a
Plan of Distribution (the "Plan") pursuant to Rule 12b-1 under the Act pursuant
to which the Fund pays the Distributor compensation, accrued daily and payable
monthly, at an 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 shares
since the Fund's inception (not including reinvestment of dividend or capital
gain distributions) less the average daily aggregate net asset value of the
Fund's shares redeemed since the Fund's inception upon which a contingent
deferred sales charge has been imposed or upon which such charge has been
waived; or (b) the Fund's average daily net assets. Amounts paid under the Plan
are paid to the Distributor to compensate it for the services provided and the
expenses borne by it and others in the distribution of the Fund's shares,
including the payment of commissions for sales of the Fund's shares and
incentive compensation to, and expenses of, the account executives of Dean
Witter Reynolds Inc., an affiliate of the Investment Manager and Distributor,
and other employees or selected broker-dealers who engage in or support
distribution of the Fund's 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 be
compensated under the Plan for its opportunity costs in advancing such amounts
which compensation would be in the form of a carrying charge on any unreimbursed
expenses incurred by the Distributor.
 
Provided that the Plan continues in effect, any cumulative expenses incurred by
the Distributor but not yet recovered, may be recovered through future
distribution fees from the Fund and contingent deferred sales charges from the
Fund's shareholders.
 
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
contingent deferred sales charges 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. The Distributor has advised the
Fund that such excess amounts, including carrying charges, total $68,120,003 at
December 31, 1996.
 
                                       41
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
NOTES TO FINANCIAL STATEMENTS DECEMBER 31, 1996, CONTINUED
 
The Distributor has informed the Fund that for the year ended December 31, 1996,
it received approximately $8,964,000 in contingent deferred sales charges from
certain redemptions of the Fund's shares.
 
4. SECURITY TRANSACTIONS AND TRANSACTIONS WITH AFFILIATES
 
The costs of purchases and sales/prepayments of portfolio securities, excluding
short-term investments, for the year ended December 31, 1996 were $541,075,742
and $1,760,020,882, respectively.
 
Dean Witter Trust Company, an affiliate of the Investment Manager and
Distributor, is the Fund's transfer agent. At December 31, 1996, the Fund had
transfer agent fees and expenses payable of approximately $546,000.
 
The Fund has an unfunded noncontributory defined benefit pension plan covering
all independent Trustees of the Fund who will have served as independent
Trustees for at least five years at the time of retirement. Benefits under this
plan are based on years of service and compensation during the last five years
of service. Aggregate pension costs for the year ended December 31, 1996
included in Trustees' fees and expenses in the Statement of Operations amounted
to $1,285. At December 31, 1996, the Fund had an accrued pension liability of
$50,453 included in accrued expenses in the Statement of Assets and Liabilities.
 
5. SHARES OF BENEFICIAL INTEREST
 
Transactions in shares of beneficial interest were as follows:
<TABLE>
<CAPTION>
                                                                                                           FOR THE YEAR
                                                                                                              ENDED
                                                                           FOR THE YEAR ENDED              DECEMBER 31,
                                                                            DECEMBER 31, 1996                  1995
                                                                   -----------------------------------   ----------------
                                                                        SHARES             AMOUNT             SHARES
                                                                   ----------------   ----------------   ----------------
<S>                                                                <C>                <C>                <C>
Sold.............................................................        44,291,927   $    394,473,930         48,336,027
Reinvestment of dividends........................................        25,980,320        230,960,458         30,293,874
                                                                   ----------------   ----------------   ----------------
                                                                         70,272,247        625,434,388         78,629,901
Repurchased......................................................      (210,573,457)    (1,872,337,457)      (190,805,203)
                                                                   ----------------   ----------------   ----------------
Net decrease.....................................................      (140,301,210)  $ (1,246,903,069)      (112,175,302)
                                                                   ----------------   ----------------   ----------------
                                                                   ----------------   ----------------   ----------------
 
<CAPTION>
 
                                                                        AMOUNT
                                                                   ----------------
<S>                                                                <C>
Sold.............................................................  $    429,525,036
Reinvestment of dividends........................................       269,738,501
                                                                   ----------------
                                                                        699,263,537
Repurchased......................................................    (1,689,910,105)
                                                                   ----------------
Net decrease.....................................................  $   (990,646,568)
                                                                   ----------------
                                                                   ----------------
</TABLE>
 
                                       42
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
NOTES TO FINANCIAL STATEMENTS DECEMBER 31, 1996, CONTINUED
 
6. FEDERAL INCOME TAX STATUS
 
At December 31, 1996, the Fund had a net capital loss carryover which may be
used to offset future capital gains to the extent provided by regulations which
is available through December 31 of the following years:
 
<TABLE>
<CAPTION>
                                                IN THOUSANDS
  ---------------------------------------------------------------------------------------------------------
    1997        1998        1999        2000        2001        2002        2003        2004        Total
  ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------
  <S>         <C>         <C>         <C>         <C>         <C>         <C>         <C>         <C>
  $ 270,987   $ 108,731   $ 261,525   $ 154,964   $ 263,492   $ 118,056   $  63,667   $  49,143   $1,290,565
  ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------
  ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------   ---------
</TABLE>
 
Capital losses incurred after October 31 ("post-October" losses) within the
taxable year are deemed to arise on the first business day of the Fund's next
taxable year. The Fund incurred and will elect to defer net capital losses of
approximately $673,000 during fiscal 1996.
 
At December 31, 1996, the Fund had temporary book/tax differences primarily
attributable to post-October losses and a permanent book/tax difference
attributable to an expired capital loss carryover. To reflect reclassifications
arising from permanent book/tax differences for the year ended December 31,
1996, accumulated net realized loss was credited and paid-in-capital was charged
$277,199,313.
 
                                       43
<PAGE>
DEAN WITTER U.S. GOVERNMENT SECURITIES TRUST
FINANCIAL HIGHLIGHTS
 
Selected ratios and per share data for a share of beneficial interest
outstanding throughout each period:
 
<TABLE>
<CAPTION>
                                                           FOR THE YEAR ENDED DECEMBER 31
                  ----------------------------------------------------------------------------------------------------------------
                     1996       1995       1994        1993       1992       1991        1990       1989       1988        1987
- ----------------------------------------------------------------------------------------------------------------------------------
 
<S>               <C>         <C>        <C>        <C>         <C>        <C>        <C>         <C>        <C>        <C>
PER SHARE OPERATING
PERFORMANCE:
 
Net asset value,
 beginning of
 period.......... $     9.21  $    8.41  $    9.31  $     9.30  $    9.52  $    9.37  $     9.51  $    9.42  $    9.75  $    10.33
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
 
Net investment
 income..........       0.56       0.57       0.58        0.64       0.74       0.87        0.90       0.91       0.97        0.96
Net realized and
 unrealized gain
 (loss)..........      (0.29)      0.80      (0.90)       0.01      (0.22)      0.15       (0.14)      0.09      (0.33)      (0.58)
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
 
Total from
 investment
 operations......       0.27       1.37      (0.32)       0.65       0.52       1.02        0.76       1.00       0.64        0.38
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
 
Less dividends
 from net
 investment
 income..........      (0.56)     (0.57)     (0.58)      (0.64)     (0.74)     (0.87)      (0.90)     (0.91)     (0.97)      (0.96)
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
 
Net asset value,
 end of period... $     8.92  $    9.21  $    8.41  $     9.31  $    9.30  $    9.52  $     9.37  $    9.51  $    9.42  $     9.75
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
                  ----------  ---------  ---------  ----------  ---------  ---------  ----------  ---------  ---------  ----------
 
TOTAL INVESTMENT
RETURN+..........       3.16%     16.74%     (3.51)%       7.13%      5.76%     11.43%       8.49%     11.10%      6.74%       3.92%
 
RATIOS TO AVERAGE
NET ASSETS:
Expenses.........       1.25%      1.24%      1.22%       1.18%      1.20%      1.17%       1.23%      1.19%      1.21%       1.18%
 
Net investment
 income..........       6.28%      6.44%      6.57%       6.78%      7.91%      9.23%       9.60%      9.62%     10.01%       9.63%
 
SUPPLEMENTAL DATA:
Net assets, end
 of period, in
 millions........     $6,450     $7,955     $8,211     $12,235    $12,484    $11,736      $9,829    $10,167    $10,366     $10,418
 
Portfolio
 turnover rate...          8%        14%        26%         32%        40%       104%         54%        44%        15%         51%
</TABLE>
 
<TABLE>
<C>  <S>
<FN>
 
- ---------------------
 +   Does not reflect the deduction of sales charge. Calculated based on the net
     asset value as of the last business day of the period.
</TABLE>
 
                       SEE NOTES TO FINANCIAL STATEMENTS
 
                                       44


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