PIMCO FUNDS
497, 1998-12-11
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<PAGE>

                            PIMCO FUNDS PROSPECTUS

<TABLE> 

<C>                 <S>                               <C>
Pacific             SHORT-TERM BOND FUNDS             INTERNATIONAL BOND FUNDS
Investment          Money Market Fund                 Global Bond Fund II
Management          Short-Term Fund                   Foreign Bond Fund
Series              Low Duration Fund                 Emerging Markets Bond Fund

December 11, 1998   

Share Classes
A  B  C
                    INTERMEDIATE-TERM BOND FUNDS      STOCK AND BOND FUNDS
                    Real Return Bond Fund             Strategic Balanced Fund
                    Total Return Fund
                    High Yield Fund                   STOCK FUNDS
                                                      StocksPLUS Fund

                    LONG-TERM BOND FUNDS
                    Municipal Bond Fund
                    Long-Term U.S. Government Fund          
</TABLE> 

                                                                       P I M C O
                                                                       ---------
                                                                           FUNDS
<PAGE>
 
            PIMCO Funds: Pacific Investment Management Series
            Prospectus
            December 11, 1998
 
            PIMCO Funds (the "Trust") is an open-end series management invest-
            ment company offering thirteen separate investment portfolios
            (each a "Fund") in this Prospectus, each with different investment
            objectives and strategies. The Trust is designed to provide access
            to the professional investment management services offered by Pa-
            cific Investment Management Company ("Pacific Investment Manage-
            ment"), which serves as investment adviser (the "Adviser") to the
            Funds. The address of PIMCO Funds is 840 Newport Center Drive,
            Suite 300, Newport Beach, CA 92660.
 
            Each Fund offers three classes of shares in this Prospectus: Class
            A shares (generally sold subject to an initial sales charge),
            Class B shares (sold subject to a contingent deferred sales
            charge) and Class C shares (sold subject to an asset based sales
            charge). Through separate prospectuses, certain Funds and other
            series of the Trust may offer up to three additional classes of
            shares, Class D, Institutional Class and Administrative Class
            shares. See "Alternative Purchase Arrangements."
 
            This Prospectus concisely describes the information investors
            should know before investing in Class A, Class B or Class C shares
            of the Funds. Please read this Prospectus carefully and keep it
            for further reference. Information about the investment objective
            of each Fund, along with a detailed description of the types of
            securities in which each Fund may invest and of investment poli-
            cies and restrictions applicable to each Fund, are set forth in
            this Prospectus. There can be no assurance that the investment ob-
            jective of any Fund will be achieved. Because the market value of
            each Fund's investments will change, the investment returns and
            net asset value per share of each Fund will vary.
 
            A Statement of Additional Information, dated November 25, 1998, as
            amended or supplemented from time to time, is available free of
            charge by writing to PIMCO Funds Distributors LLC (the "Distribu-
            tor"), 2187 Atlantic Street, Stamford, Connecticut 06902, or by
            telephoning 1-800-426-0107. The Statement of Additional Informa-
            tion, which contains more detailed information about the Trust,
            has been filed with the Securities and Exchange Commission and is
            incorporated by reference in this Prospectus. The Securities and
            Exchange Commission maintains an Internet World Wide Web site (at
            www.sec.gov) which contains the Statement of Additional Informa-
            tion, materials that are incorporated by reference into this Pro-
            spectus and the Statement of Additional Information, and other in-
            formation about the Funds.
 
            THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SE-
            CURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMIS-
            SION, 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 OF-
            FENSE.
 
            SHARES OF THE FUNDS ARE NOT DEPOSITS OR OBLIGATIONS OF, OR GUARAN-
            TEED OR ENDORSED BY, ANY FINANCIAL INSTITUTION, AND THE SHARES ARE
            NOT FEDERALLY INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORA-
            TION, THE FEDERAL RESERVE BOARD OR ANY OTHER AGENCY, AND ENTAIL
            RISK, INCLUDING THE POSSIBLE LOSS OF PRINCIPAL.
 
            INVESTMENT IN THE MONEY MARKET FUND (OR IN ANY OTHER FUND) IS NEI-
            THER INSURED NOR GUARANTEED BY THE U.S. GOVERNMENT. THERE CAN BE
            NO ASSURANCE THAT THE MONEY MARKET FUND WILL BE ABLE TO MAINTAIN A
            STABLE NET ASSET VALUE OF $1.00 PER SHARE.
 
            EACH OF THE FUNDS, EXCEPT THE MONEY MARKET FUND AND THE MUNICIPAL
            BOND FUND, MAY INVEST ALL OF ITS ASSETS IN DERIVATIVE INSTRUMENTS,
            SOME OF WHICH MAY BE PARTICULARLY SENSITIVE TO CHANGES IN PREVAIL-
            ING INTEREST RATES. UNEXPECTED CHANGES IN INTEREST RATES MAY AD-
            VERSELY AFFECT THE VALUE OF A FUND'S INVESTMENTS IN PARTICULAR DE-
            RIVATIVE INSTRUMENTS.
 
            THE HIGH YIELD AND EMERGING MARKETS BOND FUNDS MAY INVEST ALL OF
            THEIR ASSETS IN JUNK BONDS, WHICH ARE SUBJECT TO HIGH RISK, AND
            SPECULATIVE WITH REGARD TO PAYMENT OF INTEREST AND RETURN OF PRIN-
            CIPAL. INVESTORS SHOULD CAREFULLY CONSIDER THESE RISKS BEFORE IN-
            VESTING IN THE HIGH YIELD FUND. SEE "CHARACTERISTICS AND RISKS OF
            SECURITIES AND INVESTMENT TECHNIQUES--HIGH YIELD SECURITIES ("JUNK
            BONDS")."
 
 
              TABLE OF CONTENTS
 
<TABLE>
<S>                            <C>
PIMCO Funds Overview..........   3
Financial Highlights..........   8
Investment Objectives and
Policies......................  12
Investment Risks and
Considerations................  19
Characteristics and Risks of
 Securities
 and Investment Techniques....  20
Performance Information.......  35
How to Buy Shares.............  37
Alternative Purchase
Arrangements..................  41
Exchange Privilege............  50
</TABLE>
<TABLE>
<S>                                <C>
How to Redeem.....................  51
Distributor and Distribution and
Servicing Plans...................  55
How Net Asset Value Is Determined
 ..................................  58
Distributions.....................  59
Taxes.............................  60
Management of the Trust...........  61
Description of the Trust..........  64
Mailings to Shareholders..........  65
Appendix A--Description of
Duration..........................  66
Appendix B--Description of
Securities Ratings................  67
</TABLE>
 PIMCO Funds: Pacific Investment Management Series
2
<PAGE>
 
 
            PIMCO Funds Overview
            Pacific Investment Management, a subsidiary of PIMCO Advisors
            L.P., is the investment adviser of all the Funds. Pacific Invest-
            ment Management is one of the premier fixed income investment man-
            agement firms in the U.S. As of September 30, 1998, Pacific In-
            vestment Management had approximately $148 billion in assets under
            management. Pacific Investment Management invests in all sectors
            of the fixed income market, using its total return philosophy--
            seeking capital appreciation as well as yield.
 
<TABLE>
<CAPTION>
                            PIMCO                     PRIMARY
                            FUND NAME                 OBJECTIVE                              DURATION          CREDIT QUALITY(/1/)
              ---------------------------------------------------------------------------------------------------------
           <S>              <C>                       <C>                                    <C>               <C>
           SHORT-TERM BOND
            FUNDS           Money Market              Maximum current income, consistent     ^ 90 days dollar- Min 95% Aaa or
                                                      with preservation of capital and       weighted average  Prime 1; ^ 5% Aa
                                                      daily liquidity                        maturity          or Prime 2
                            ---------------------------------------------------------------------------------
                            Short-Term                Maximum current income, consistent     0-1 year          B to Aaa; max
                                                      with preservation of capital and                         10% below Baa
                                                      daily liquidity
                            ---------------------------------------------------------------------------------
                            Low Duration              Maximum total return consistent        1-3 years         B to Aaa; max-
                                                      with preservation of real capital                        10% below Baa
                                                      and prudent investment management
              ---------------------------------------------------------------------------------------------------------
           INTERMEDIATE-    Real Return Bond          Maximum real return, consistent        Not applicable,   B to Aaa; max
           TERM                                       with preservation of real capital      but see Fund      10% below Baa
           BOND FUNDS
                                                      and prudent investment management      description
                            ---------------------------------------------------------------------------------
                            Total Return              Maximum total return, consistent       3-6 years         B to Aaa; max
                                                      with preservation of capital                             10% below Baa
                                                      and prudent investment management
                            ---------------------------------------------------------------------------------
                            High Yield                Maximum total return, consistent       2-6 years         B to Aaa; min
                                                      with preservation of capital                             65% below Baa
                                                      and prudent investment management
              ---------------------------------------------------------------------------------------------------------
           LONG-TERM BOND
            FUNDS           Municipal Bond            High current income exempt from        3-10 years        Ba to Aaa; max
                                                      federal income tax, consistent with                      10% below Baa
                                                      preservation of capital
                            ---------------------------------------------------------------------------------
                            Long-Term U.S. Government Maximum total return, consistent       18 years          A to Aaa
                                                      with preservation of capital
                                                      and prudent investment management
              ---------------------------------------------------------------------------------------------------------
           INTERNATIONAL    Global Bond II            Maximum total return, consistent       3-7 years         B to Aaa; max
           BOND FUNDS                                 with preservation of capital                             10% below Baa
                                                      (U.S. and non-U.S.)
                            ---------------------------------------------------------------------------------
                            Foreign Bond              Maximum total return, consistent       3-7 years         B to Aaa; max
                                                      with preservation of capital                             10% below Baa
                                                      and prudent investment management
                                                      (non-U.S.)
                            ---------------------------------------------------------------------------------
                            Emerging Markets Bond     Maximum total return, consistent       0-8 years         B to Aaa
                                                      with preservation of capital
                                                      and prudent investment management
                                                      (non-U.S.)
              ---------------------------------------------------------------------------------------------------------
           STOCK AND BOND   Strategic Balanced        Maximum total return, consistent       0-6 years         B to Aaa; max
            FUNDS
                                                      with preservation of capital                             10% below Baa
                                                      and prudent investment management
              ---------------------------------------------------------------------------------------------------------
           STOCK FUNDS      StocksPLUS(/2/)           Total return which exceeds that of the 0-1 year          B to Aaa; max
                                                      S&P 500                                                  10% below Baa
</TABLE>
 
FUND
PROFILES
            1. As rated by Moody's Investors Service, Inc., or if unrated, de-
            termined to be of comparable quality. For specific information
            concerning the credit quality of the securities in each Fund's
            portfolio, see "Investment Objectives and Policies."
            2. The StocksPLUS Fund may invest all of its assets in stock index
            futures backed by short-term bonds.
                                                                    Prospectus
                                                                               3
<PAGE>
 
 
 
 
<TABLE>
<CAPTION>
                                      CLASS A     CLASS B     CLASS C
                                      SHARES      SHARES      SHARES
              ----------------------------------------------------------
          <S>                         <C>         <C>         <C>
          MAXIMUM INITIAL SALES
           CHARGE IMPOSED ON
           PURCHASES
           (as a percentage of
           offering price at time
           of purchase)
            TOTAL RETURN, HIGH
             YIELD, LONG-TERM U.S.
             GOVERNMENT, GLOBAL
             BOND II, FOREIGN BOND,
             EMERGING MARKETS BOND
             AND STRATEGIC BALANCED
             FUNDS                     4.50%       None        None
            LOW DURATION, REAL
             RETURN BOND, MUNICIPAL
             BOND AND STOCKSPLUS
             FUNDS                     3.00%       None        None
            SHORT-TERM FUND            2.00%       None        None
            MONEY MARKET FUND           None(/1/)  None        None
              ----------------------------------------------------------
          MAXIMUM SALES CHARGE
           IMPOSED ON REINVESTED
           DIVIDENDS
           (as a percentage of net
           asset value at time of
           purchase)                    None       None        None
              ----------------------------------------------------------
          MAXIMUM CONTINGENT
           DEFERRED SALES CHARGE
           ("CDSC")
           (as a percentage of
           original purchase price)       1%(/2/)    5%(/3/)     1%(/4/)
              ----------------------------------------------------------
          EXCHANGE FEE                  None(/1/)  None        None
</TABLE>
 
SHAREHOLDER
TRANSACTION
EXPENSES
 
            1. Regular sales charges apply when Class A shares of the Money
            Market Fund (on which no sales charge was paid at time of pur-
            chase) are exchanged for shares of any other Fund.
            2. Imposed only in certain circumstances where Class A shares are
            purchased without a front-end sales charge at the time of pur-
            chase. See "Alternative Purchase Arrangements" in this Prospectus.
            3. The maximum CDSC is imposed on shares redeemed in the first
            year. For shares held longer than one year, the CDSC declines ac-
            cording to the schedule set forth under "Alternative Purchase Ar-
            rangements--Deferred Sales Charge Alternative--Class B Shares" in
            this Prospectus.
            4. The CDSC on Class C shares is imposed only on shares redeemed
            in the first year.
 
 
<TABLE>
<CAPTION>
                                                                            EXAMPLE: You would EXAMPLE: You would
                                                                            pay the            pay the
                                                                            following expenses
                                                                            on a $1,000        following expenses
                                                                            investment         on a $1,000
                                                                            assuming (1) 5%    investment
                                                                            annual return and  assuming (1) 5%
                                                                            (2) redemption at  annual return and
                                  ANNUAL FUND OPERATING EXPENSES            the end of each    (2) no redemption:
                                  (As a percentage of average net assets):  time period:
                                                                 TOTAL
                                            ADMINI-              FUND
                                  ADVISORY  STRATIVE  12B-1      OPERATING  YEAR               YEAR
           FUND                   FEE       FEE       FEES(/1/)  EXPENSES   1    3   5    10   1    3   5    10
              ---------------------------------------------------------------------------------------------------
           <S>                    <C>       <C>       <C>        <C>        <C>  <C> <C>  <C>  <C>  <C> <C>  <C>
           MONEY MARKET           .15%      .35%      .10%(/2/)   .60%(/3/) $ 6  $19 $ 33 $ 75 $ 6  $19 $ 33 $ 75
              ---------------------------------------------------------------------------------------------------
           SHORT-TERM             .25       .35       .25         .85        29   47   66  123  29   47   66  123
              ---------------------------------------------------------------------------------------------------
           LOW DURATION           .25       .40       .25         .90        39   58   78  137  39   58   78  137
              ---------------------------------------------------------------------------------------------------
           REAL RETURN BOND       .25       ,40       .25         .90        39   58   78  137  39   58   78  137
              ---------------------------------------------------------------------------------------------------
           TOTAL RETURN           .25       .40       .25         .90        54   72   93  151  54   72   93  151
              ---------------------------------------------------------------------------------------------------
           HIGH YIELD             .25       .40       .25         .90        54   72   93  151  54   72   93  151
              ---------------------------------------------------------------------------------------------------
           MUNICIPAL BOND         .25       .35       .25         .85        38   56  N/A  N/A  38   56  N/A  N/A
              ---------------------------------------------------------------------------------------------------
           LONG-TERM U.S.
           GOVERNMENT             .25       .40       .25         .90        54   72   93  151  54   72   93  151
              ---------------------------------------------------------------------------------------------------
           GLOBAL BOND II         .25       .45       .25         .95        54   74   95  156  54   74   95  156
              ---------------------------------------------------------------------------------------------------
           FOREIGN BOND           .25       .45       .25         .95        54   74   95  156  54   74   95  156
              ---------------------------------------------------------------------------------------------------
           EMERGING MARKETS BOND  .45       .55       .25        1.25        57   83  111  189  57   83  111  189
              ---------------------------------------------------------------------------------------------------
           STRATEGIC BALANCED     .40       .40       .25        1.05        55   77  100  167  55   77  100  167
              ---------------------------------------------------------------------------------------------------
           STOCKSPLUS             .40       .40       .25        1.05        40   62   86  154  40   62   86  154
              ---------------------------------------------------------------------------------------------------
</TABLE>
 
 
CLASS A
SHARES
 
            1. 12b-1 fees represent servicing fees which are paid to the Dis-
            tributor and repaid to participating brokers, certain banks and
            other financial intermediaries. See "Distributor and Distribution
            and Servicing Plans."
            2. The Distributor has voluntarily undertaken to reduce the 12b-1
            fee it receives with respect to the Money Market Fund to .10% of
            the Fund's average daily net assets until further notice. Absent
            such undertaking, the 12b-1 fee would be .20% of the Fund's aver-
            age daily net assets.
            3. Absent the undertaking noted, the "Total Fund Operating Ex-
            penses" for the Money Market Fund would be .70% of the Fund's av-
            erage daily net assets.
 
 PIMCO Funds: Pacific Investment Management Series
4
<PAGE>
 
 
 
<TABLE>
<CAPTION>
                                                                                EXAMPLE: You would EXAMPLE: You would
                                                                                pay the following  pay the following
                                                                                expenses on a      expenses on a
                                                                                $1,000 investment  $1,000 investment
                                                                                assuming (1) 5%    assuming (1) 5%
                                                                                annual return and  annual return and
                                                                                (2) redemption at  (2) no redemption:
                                  ANNUAL FUND OPERATING EXPENSES                the end of each
                                  (As a percentage of average net assets):      time period:
                                                                    TOTAL
                                             ADMINI-                FUND
                                  ADVISORY   STRATIVE   12B-1       OPERATING   YEAR               YEAR
           FUND                   FEE        FEE        FEES(/1/)   EXPENSES    1    3   5    10   1    3   5    10
              -------------------------------------------------------------------------------------------------------
           <S>                    <C>        <C>        <C>         <C>         <C>  <C> <C>  <C>  <C>  <C> <C>  <C>
           MONEY MARKET                 .15%       .35%       1.00%       1.50% $65  $77 $102 $143 $15  $47 $ 82 $143
              -------------------------------------------------------------------------------------------------------
           SHORT-TERM                   .25        .35        1.00        1.60   66   80  107  160  16   50   87  160
              -------------------------------------------------------------------------------------------------------
           LOW DURATION                 .25        .40        1.00        1.65   67   82  110  166  17   52   90  166
CLASS B       -------------------------------------------------------------------------------------------------------
SHARES     REAL RETURN BOND             .25        .40        1.00        1.65   67   82  110  166  17   52   90  166
              -------------------------------------------------------------------------------------------------------
           TOTAL RETURN                 .25        .40        1.00        1.65   67   82  110  166  17   52   90  166
              -------------------------------------------------------------------------------------------------------
           HIGH YIELD                   .25        .40        1.00        1.65   67   82  110  166  17   52   90  166
              -------------------------------------------------------------------------------------------------------
           MUNICIPAL BOND               .25        .35        1.00        1.60   66   80  N/A  N/A  16   50  N/A  N/A
              -------------------------------------------------------------------------------------------------------
           LONG-TERM U.S.
           GOVERNMENT                   .25        .40        1.00        1.65   67   82  110  166  17   52   90  166
              -------------------------------------------------------------------------------------------------------
           GLOBAL BOND II               .25        .45        1.00        1.70   67   84  112  171  17   54   92  171
              -------------------------------------------------------------------------------------------------------
           FOREIGN BOND                 .25        .45        1.00        1.70   67   84  112  171  17   54   92  171
              -------------------------------------------------------------------------------------------------------
           EMERGING MARKETS BOND        .45        .55        1.00        2.00   70   93  128  204  20   63  108  204
              -------------------------------------------------------------------------------------------------------
           STRATEGIC BALANCED           .40        .40        1.00        1.80   68   87  117  182  18   57   97  182
              -------------------------------------------------------------------------------------------------------
           STOCKSPLUS                   .40        .40        1.00        1.80   68   87  117  182  18   57   97  182
              -------------------------------------------------------------------------------------------------------
</TABLE>
            1. 12b-1 fees which equal or are less than .25% represent servic-
            ing fees which are paid to the Distributor and repaid to partici-
            pating brokers, certain banks and other financial intermediaries.
            12b-1 fees which exceed .25% represent aggregate distribution and
            servicing fees. See "Distributor and Distribution and Servicing
            Plans."
                                                                    Prospectus
                                                                               5
<PAGE>
 
 
 
<TABLE>
<CAPTION>
                                                                                                             EXAMPLE: You
                                                                                          EXAMPLE: You would would pay the
                                                                                          pay the following  following
                                                                                          expenses on a      expenses on a
                                                                                          $1,000 investment  $1,000 investment
                                                                                          assuming (1) 5%    assuming (1) 5%
                                                                                          annual return and  annual return and
                                                                                          (2) redemption at  (2) no
                                  ANNUAL FUND OPERATING EXPENSES                          the end of each    redemption:
                                  (As a percentage of average net assets):                time period:
                                                                         TOTAL
                                             ADMINI-                     FUND
                                  ADVISORY   STRATIVE   12B-1            OPERATING        YEAR               YEAR
           FUND                   FEE        FEE        FEES(/1/)        EXPENSES         1    3   5    10   1    3   5   10
              ---------------------------------------------------------------------------------------------------------
           <S>                    <C>        <C>        <C>              <C>              <C>  <C> <C>  <C>  <C>  <C> <C> <C>
           MONEY MARKET                 .15%       .35%        .10(/2/)%        .60(/3/)% $16  $19 $ 33 $ 75 $ 6  $19 $33 $ 75
              ---------------------------------------------------------------------------------------------------------
           SHORT-TERM                   .25        .35         .55(/2/)        1.15(/3/)   22   37   63  140  12   37  63  140
              ---------------------------------------------------------------------------------------------------------
           LOW DURATION                 .25        .40         .75             1.40        24   44   77  168  14   44  77  168
              ---------------------------------------------------------------------------------------------------------
           REAL RETURN BOND             .25        .40         .75(/2/)        1.40(/3/)   24   44   77  168  14   44  77  168
              ---------------------------------------------------------------------------------------------------------
           TOTAL RETURN                 .25        .40        1.00             1.65        27   52   90  195  17   52  90  195
              ---------------------------------------------------------------------------------------------------------
           HIGH YIELD                   .25        .40        1.00             1.65        27   52   90  195  17   52  90  195
              ---------------------------------------------------------------------------------------------------------
           MUNICIPAL BOND               .25        .35         .75(/2/)        1.35(/3/)   24   43  N/A  N/A  14   43 N/A  N/A
              ---------------------------------------------------------------------------------------------------------
           LONG-TERM U.S.
           GOVERNMENT                   .25        .40        1.00             1.65        27   52   90  195  17   52  90  195
              ---------------------------------------------------------------------------------------------------------
           GLOBAL BOND II               .25        .45        1.00             1.70        27   54   92  201  17   54  92  201
              ---------------------------------------------------------------------------------------------------------
           FOREIGN BOND                 .25        .45        1.00             1.70        27   54   92  201  17   54  92  201
              ---------------------------------------------------------------------------------------------------------
           EMERGING MARKETS BOND        .45        .55        1.00             2.00        30   63  108  233  20   63 108  233
              ---------------------------------------------------------------------------------------------------------
           STRATEGIC BALANCED           .40        .40        1.00             1.80        28   57   97  212  18   57  97  212
              ---------------------------------------------------------------------------------------------------------
           STOCKSPLUS                   .40        .40         .75(/2/)        1.55(/3/)   26   49   84  185  16   49  84  185
              ---------------------------------------------------------------------------------------------------------
</TABLE>
 
CLASS C
SHARES
            1. 12b-1 fees which equal or are less than .25% represent servic-
            ing fees which are paid to the Distributor and repaid to partici-
            pating brokers, certain banks and other financial intermediaries.
            12b-1 fees which exceed .25% represent aggregate distribution and
            servicing fees. See "Distributor and Distribution and Servicing
            Plans."
            2. The Distributor has voluntarily undertaken to reduce the 12b-1
            fee it may receive with respect to each of the Money Market,
            Short-Term, Real Return Bond, Municipal Bond and StocksPLUS Funds
            to the following annual rates based on the Fund's average daily
            net assets until further notice: Money Market--.10%; Short-Term--
            .55%; Real Return Bond--.75%; Municipal Bond--.75%; and
            StocksPLUS--.75%. Absent such undertakings, the 12b-1 fee for each
            such Fund would be as follows: Money Market--.20%; Short-Term--
            1.00%; Real Return Bond--1.00%; Municipal Bond--1.00%; and
            StocksPLUS--1.00%.
            3. Absent the undertakings noted, the "Total Fund Operating Ex-
            penses" for the Money Market, Short-Term, Real Return Bond, Munic-
            ipal Bond and StocksPLUS Funds would be as follows (based on aver-
            age daily net assets): Money Market--.70%; Short-Term--1.60%; Real
            Return Bond--1.65%; Municipal Bond--1.60%; and StocksPLUS--1.80%.
 
            The purpose of the foregoing tables is to assist investors in un-
            derstanding the various costs and expenses of the Trust that are
            borne directly or indirectly by Class A, Class B and Class C
            shareholders of the Funds. The information is based upon each
            Funds' current fees and expenses. The Examples for Class A shares
            assume payment of the current maximum applicable sales load. Due
            to the 12b-1 distribution fee imposed on Class B and Class C
            shares, a Class B or Class C shareholder of the Trust may, depend-
            ing on the length of time the shares are held, pay more than the
            economic equivalent of the maximum front-end sales charges permit-
            ted by relevant rules of the National Association of Securities
            Dealers, Inc.
 
            NOTE: THE FIGURES SHOWN IN THE EXAMPLES ARE ENTIRELY HYPOTHETICAL.
            THEY ARE NOT REPRESENTATIONS OF PAST OR FUTURE PERFORMANCE OR EX-
            PENSES; ACTUAL PERFORMANCE AND/OR EXPENSES MAY BE MORE OR LESS
            THAN SHOWN.
 PIMCO Funds: Pacific Investment Management Series
6
<PAGE>
 
                      (This page left blank intentionally)
                                                                    Prospectus
                                                                               7
<PAGE>
 
 
Financial Highlights
The following information regarding selected per share data and ratios for
shares of certain of the Funds is part of the Trust's audited financial state-
ments, which are included in the Trust's Annual Report dated March 31, 1998,
which is incorporated by reference in the Statement of Additional Information.
The Trust's audited financial statements and selected per share data and ratios
appearing below have been examined by PricewaterhouseCoopers LLP, independent
accountants, whose opinion thereon is also included in the Annual Report, which
may be obtained without charge. Information is presented for each Fund de-
scribed herein which had investment operations during the reporting periods.
Information regarding the Global Bond Fund II reflects the operational history
of the Global Income Fund, a former series of PIMCO Advisors Funds that was re-
organized as a series of the Trust on January 17, 1997.
 
Selected data for a share outstanding throughout each period:
 
<TABLE>
<CAPTION>
                 NET ASSET              NET REALIZED  TOTAL INCOME DIVIDENDS  DIVIDENDS IN  DISTRIBUTIONS DISTRIBUTIONS
        YEAR OR    VALUE      NET      AND UNREALIZED (LOSS) FROM   FROM NET  EXCESS OF NET   FROM NET    IN EXCESS OF
         PERIOD  BEGINNING INVESTMENT  GAIN (LOSS) ON  INVESTMENT  INVESTMENT  INVESTMENT     REALIZED    NET REALIZED
         ENDED   OF PERIOD   INCOME     INVESTMENTS    OPERATIONS    INCOME      INCOME     CAPITAL GAINS CAPITAL GAINS
- -----------------------------------------------------------------------------------------------------------------------
<S>              <C>       <C>         <C>            <C>          <C>        <C>           <C>           <C>
MONEY MARKET FUND
 Class A
 03/31/98         $ 1.00     $0.05(+)      $ 0.00 (+)    $0.05       $(0.05)     $ 0.00        $ 0.00        $ 0.00
 03/31/97(a)        1.00      0.01           0.00         0.01        (0.01)       0.00          0.00          0.00
 Class B
 03/31/98           1.00      0.04(+)        0.00 (+)     0.04        (0.04)       0.00          0.00          0.00
 03/31/97(a)        1.00      0.01           0.00         0.01        (0.01)       0.00          0.00          0.00
 Class C
 03/31/98           1.00      0.05(+)        0.00 (+)     0.05        (0.05)       0.00          0.00          0.00
 03/31/96(a)        1.00      0.01           0.00         0.01        (0.01)       0.00          0.00          0.00
SHORT-TERM FUND
 Class A
 03/31/98         $10.00     $0.55(+)      $ 0.09 (+)    $0.64       $(0.56)     $(0.01)       $ 0.00        $ 0.00
 03/31/97(b)       10.04      0.10          (0.03)        0.07        (0.10)      (0.01)         0.00          0.00
 Class B
 03/31/98          10.00      0.50(+)        0.08 (+)     0.58        (0.50)      (0.01)         0.00          0.00
 03/31/97(b)       10.04      0.09          (0.03)        0.06        (0.10)       0.00          0.00          0.00
 Class C
 03/31/98          10.00      0.54(+)        0.07 (+)     0.61        (0.53)      (0.01)         0.00          0.00
 03/31/97(b)       10.04      0.09          (0.03)        0.06        (0.10)       0.00          0.00          0.00
LOW DURATION FUND
 Class A
 03/31/98         $ 9.98     $0.60(+)      $ 0.23 (+)    $0.83       $(0.58)     $(0.02)       $(0.03)       $ 0.00
 03/31/97(a)       10.02      0.12          (0.03)        0.09        (0.12)      (0.01)         0.00          0.00
 Class B
 03/31/98           9.98      0.53(+)        0.22 (+)     0.75        (0.50)      (0.02)        (0.03)         0.00
 03/31/97(a)       10.02      0.10          (0.03)        0.07        (0.11)       0.00          0.00          0.00
 Class C
 03/31/98           9.98      0.55(+)        0.23 (+)     0.78        (0.53)      (0.02)        (0.03)         0.00
 03/31/97(a)       10.02      0.11          (0.03)        0.08        (0.11)      (0.01)         0.00          0.00
HIGH YIELD FUND
 Class A
 03/31/98         $11.10     $0.93(+)      $ 0.66 (+)    $1.59       $(0.94)     $ 0.00        $ 0.00        $(0.09)
 03/31/97(a)       11.18      0.17          (0.05)        0.12        (0.20)       0.00          0.00          0.00
 Class B
 03/31/98          11.10      0.84(+)        0.66 (+)     1.50        (0.85)       0.00          0.00         (0.09)
 03/31/97(a)       11.18      0.15          (0.05)        0.10        (0.18)       0.00          0.00          0.00
 Class C
 03/31/98          11.10      0.85(+)        0.65 (+)     1.50        (0.85)       0.00          0.00         (0.09)
 03/31/97(a)       11.18      0.15          (0.05)        0.10        (0.18)       0.00          0.00          0.00
</TABLE>
- -------
(+)Per share amounts based on average number of shares outstanding during the
period.
(a)From commencement of operations, January 13, 1997.
(b)From commencement of operations, January 20, 1997.
 PIMCO Funds: Pacific Investment Management Series
8
<PAGE>
 
 
                        FINANCIAL HIGHLIGHTS (CONTINUED)
<TABLE>
<CAPTION>
                                                                   RATIO OF NET
                          NET ASSET         NET ASSETS  RATIO OF    INVESTMENT
TAX BASIS                   VALUE              END     EXPENSES TO  INCOME TO   PORTFOLIO
  RETURN        TOTAL        END    TOTAL   OF PERIOD    AVERAGE     AVERAGE    TURNOVER
OF CAPITAL  DISTRIBUTIONS OF PERIOD RETURN   (000'S)   NET ASSETS   NET ASSETS    RATE
- -----------------------------------------------------------------------------------------
<S>         <C>           <C>       <C>     <C>        <C>         <C>          <C>
  $0.00        $ (0.05)    $ 1.00    5.10%   $ 41,375     0.60%        5.02%       N/A
   0.00          (0.01)      1.00    1.01      43,589     0.57+        4.44+       N/A
   0.00          (0.04)      1.00    4.21       2,937     1.50         4.15        N/A
   0.00          (0.01)      1.00    0.83       3,143     1.41+        3.62+       N/A
   0.00          (0.05)      1.00    5.14      55,696     0.60         5.05        N/A
   0.00          (0.01)      1.00    1.02      85,398     0.58+        4.47+       N/A
  $0.00        $ (0.58)    $10.06    6.64%   $ 24,182     0.85%        5.48%        48%
   0.00          (0.11)     10.00    0.66       2,533     0.86+        5.07+        77
   0.00          (0.52)     10.06    5.96       1,258     1.60         4.97         48
   0.00          (0.10)     10.00    0.58         114     1.62+        4.83+        77
   0.00          (0.55)     10.06    6.33       6,763     1.15         5.33         48
   0.00          (0.10)     10.00    0.63       1,359     1.14+        4.78+        77
  $0.00         $(0.63)    $10.18    8.49%   $109,531     0.90%        5.93%       309%
   0.00          (0.13)      9.98    0.85      59,348     0.91+        5.84+       240
   0.00          (0.55)     10.18    7.68      17,624     1.65         5.16        309
   0.00          (0.11)      9.98    0.68       5,296     1.67+        5.03+       240
   0.00          (0.58)     10.18    8.01      68,766     1.40         5.46        309
   0.00          (0.12)      9.98    0.75      63,606     1.42+        5.36+       240
  $0.00        $()1.03)    $11.66   14.80%   $ 70,858     0.90%        8.02%        37%
   0.00          (0.20)     11.10    1.06      28,873     0.92+        8.28+        67
   0.00          (0.94)     11.66   13.94     156,099     1.65         7.27         37
   0.00          (0.18)     11.10    0.86      60,269     1.67+        7.52+        67
   0.00          (0.94)     11.66   13.95     284,836     1.65         7.36         37
   0.00          (0.18)     11.10    0.88     205,297     1.68+        7.56+        67
</TABLE>
- -------
 +Annualized.
                                                                    Prospectus
                                                                               9
<PAGE>
 
 
                        FINANCIAL HIGHLIGHTS (CONTINUED)
 
<TABLE>
<CAPTION>
                    NET ASSET               NET REALIZED  TOTAL INCOME DIVIDENDS  DIVIDENDS IN  DISTRIBUTIONS DISTRIBUTIONS
        YEAR OR       VALUE      NET       AND UNREALIZED (LOSS) FROM   FROM NET  EXCESS OF NET   FROM NET    IN EXCESS OF
         PERIOD     BEGINNING INVESTMENT   GAIN (LOSS) ON  INVESTMENT  INVESTMENT  INVESTMENT     REALIZED    NET REALIZED
         ENDED      OF PERIOD   INCOME      INVESTMENTS    OPERATIONS    INCOME      INCOME     CAPITAL GAINS CAPITAL GAINS
- -------------------------------------------------------------------------------------------------------------------------------
<S>                 <C>       <C>          <C>            <C>          <C>        <C>           <C>           <C>           <C>
TOTAL RETURN FUND
 Class A
 03/31/98            $10.27     $ 0.58 (+)     $ 0.63 (+)    $ 1.21      $(0.57)     $(0.02)       $(0.27)        $0.00
 03/31/97(a)          10.40       0.12          (0.12)         0.00       (0.13)       0.00          0.00          0.00
 Class B
 03/31/98             10.27       0.50 (+)       0.63 (+)      1.13       (0.50)      (0.01)        (0.27)         0.00
 03/31/97(a)          10.40       0.11          (0.12)        (0.01)      (0.12)       0.00          0.00          0.00
 Class C
 03/31/98             10.27       0.51 (+)       0.63 (+)      1.14       (0.51)      (0.01)        (0.27)         0.00
 03/31/97(a)          10.40       0.11          (0.12)        (0.01)      (0.12)       0.00          0.00          0.00
REAL RETURN BOND FUND
 Class A
 03/31/98            $ 9.93     $ 0.40 (+)     $ 0.03 (+)    $ 0.43      $(0.42)     $(0.03)       $(0.14)        $0.00
 03/31/97(c)          10.00       0.11 (+)      (0.10)(+)      0.01       (0.08)       0.00          0.00          0.00
 Class B
 03/31/98              9.93       0.33 (+)       0.03 (+)      0.36       (0.36)      (0.02)        (0.14)         0.00
 03/31/97(c)          10.00       0.09          (0.10)        (0.01)      (0.06)       0.00          0.00          0.00
 Class C
 03/31/98              9.93       0.35 (+)       0.04 (+)      0.39       (0.38)      (0.03)        (0.14)         0.00
 03/31/97(c)          10.00       0.09          (0.10)        (0.01)      (0.06)       0.00          0.00          0.00
LONG-TERM U.S. GOVERNMENT FUND
 Class A
 03/31/98            $ 9.39     $ 0.48 (+)     $ 1.34 (+)    $ 1.82      $(0.58)     $ 0.00        $(0.06)        $0.00
 03/31/97(b)           9.67       0.32          (0.47)        (0.15)      (0.13)       0.00          0.00          0.00
 Class B
 03/31/98              9.39       0.39 (+)       1.35 (+)      1.74       (0.50)       0.00         (0.06)         0.00
 03/31/97(b)           9.67       0.29          (0.47)        (0.18)      (0.10)       0.00          0.00          0.00
 Class C
 03/31/98              9.39       0.39 (+)       1.35 (+)      1.74       (0.50)       0.00         (0.06)         0.00
 03/31/97(b)           9.67       0.29          (0.47)        (0.18)      (0.10)       0.00          0.00          0.00
FOREIGN BOND FUND
 Class A
 03/31/98            $10.41     $ 0.61 (+)     $ 0.62 (+)    $ 1.23      $(0.59)     $ 0.00        $(0.31)        $0.00
 03/31/97(b)          10.59       0.59          (0.72)        (0.13)      (0.05)       0.00          0.00          0.00
 Class B
 03/31/98             10.41       0.53 (+)       0.61 (+)      1.14       (0.50)       0.00         (0.31)         0.00
 03/31/97(b)          10.59       0.58          (0.72)        (0.14)      (0.04)       0.00          0.00          0.00
 Class C
 03/31/98             10.41       0.52 (+)       0.62 (+)      1.14       (0.50)       0.00         (0.31)         0.00
 03/31/97(b)          10.59       0.58          (0.72)        (0.14)      (0.04)       0.00          0.00          0.00
GLOBAL BOND FUND II
 Class A
 03/31/98            $10.84     $ 0.64 (+)     $ 0.51 (+)    $ 1.15      $ 0.00      $(0.54)       $(1.53)        $0.00
 10/01/96--03/31/97   10.96       0.66          (0.16)         0.50       (0.22)       0.00         (0.40)         0.00
 09/30/96(d)          10.00       0.32 (e)       0.95          1.27       (0.31)       0.00          0.00          0.00
 Class B
 03/31/98             10.84       0.66 (+)       0.41 (+)      1.07        0.00       (0.46)        (1.53)         0.00
 10/01/96--03/31/97   10.96       0.62          (0.16)         0.46       (0.18)       0.00         (0.40)         0.00
 09/30/96(d)          10.00       0.30 (e)       0.92          1.22       (0.26)       0.00          0.00          0.00
 Class C
 03/31/98             10.84       0.55 (+)       0.52 (+)      1.07        0.00       (0.46)        (1.53)         0.00
 10/01/96--03/31/97   10.96       0.62          (0.16)         0.46       (0.18)       0.00         (0.40)         0.00
 09/30/96(d)          10.00       0.30 (e)       0.92          1.22       (0.26)       0.00          0.00          0.00
EMERGING MARKETS BOND FUND
 Class A
 03/31/98(f)         $10.00     $ 0.44 (+)     $(0.18)(+)    $ 0.26      $(0.44)     $ 0.00        $(0.15)        $0.00
 Class B
 03/31/98(f)          10.00       0.40 (+)     (0.20)(+)       0.20       (0.38)       0.00         (0.15)         0.00
 Class C
 09/30/97(f)          10.00       0.38 (+)      (0.18)(+)      0.20       (0.38)       0.00         (0.15)         0.00
STOCKSPLUS FUND
 Class A
 03/31/98            $11.46     $ 1.66 (+)     $ 3.41 (+)    $ 5.07      $(1.38)     $ 0.00        $(1.09)        $0.00
 03/31/97(b)          11.91      (0.10)         (0.20)        (0.30)      (0.15)       0.00          0.00          0.00
 Class B
 03/301/98            11.44       1.61 (+)       3.35 (+)      4.96       (1.30)       0.00         (1.09)         0.00
 03/31/97(b)          11.91      (0.13)         (0.20)        (0.33)      (0.14)       0.00          0.00          0.00
 Class C
 03/31/98             11.45       1.64 (+)       3.35 (+)      4.99       (1.32)       0.00         (1.09)         0.00
 03/31/97(b)          11.91      (0.12)         (0.20)        (0.32)      (0.14)       0.00          0.00          0.00
<CAPTION>
        YEAR OR
         PERIOD
         ENDED
- -------------------------------------------------------------------------------------------------------------------------------
<S>                 <C>
TOTAL RETURN FUND
 Class A
 03/31/98
 03/31/97(a)
 Class B
 03/31/98
 03/31/97(a)
 Class C
 03/31/98
 03/31/97(a)
REAL RETURN BOND FUND
 Class A
 03/31/98
 03/31/97(c)
 Class B
 03/31/98
 03/31/97(c)
 Class C
 03/31/98
 03/31/97(c)
LONG-TERM U.S. GOVERNMENT FUND
 Class A
 03/31/98
 03/31/97(b)
 Class B
 03/31/98
 03/31/97(b)
 Class C
 03/31/98
 03/31/97(b)
FOREIGN BOND FUND
 Class A
 03/31/98
 03/31/97(b)
 Class B
 03/31/98
 03/31/97(b)
 Class C
 03/31/98
 03/31/97(b)
GLOBAL BOND FUND II
 Class A
 03/31/98
 10/01/96--03/31/97
 09/30/96(d)
 Class B
 03/31/98
 10/01/96--03/31/97
 09/30/96(d)
 Class C
 03/31/98
 10/01/96--03/31/97
 09/30/96(d)
EMERGING MARKETS BOND FUND
 Class A
 03/31/98(f)
 Class B
 03/31/98(f)
 Class C
 09/30/97(f)
STOCKSPLUS FUND
 Class A
 03/31/98
 03/31/97(b)
 Class B
 03/301/98
 03/31/97(b)
 Class C
 03/31/98
 03/31/97(b)
</TABLE>
- -------
(c)From commencement of operations, January 29, 1997.
(d)From commencement of operations, October 2, 1995.
(e)Reflects voluntary waiver of investment advisory fee of $12,041 (.01 per
share) by the Adviser.
(f)From commencement of operations, July 31, 1997.
 
10
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
 
                        FINANCIAL HIGHLIGHTS (CONTINUED)
<TABLE>
<CAPTION>
                                                                   RATIO OF NET
                          NET ASSET         NET ASSETS  RATIO OF    INVESTMENT
TAX BASIS                   VALUE              END     EXPENSES TO  INCOME TO   PORTFOLIO
  RETURN        TOTAL        END    TOTAL   OF PERIOD    AVERAGE     AVERAGE    TURNOVER
OF CAPITAL  DISTRIBUTIONS OF PERIOD RETURN   (000'S)   NET ASSETS   NET ASSETS    RATE
- -----------------------------------------------------------------------------------------
<S>         <C>           <C>       <C>     <C>        <C>         <C>          <C>
  $0.00        $(0.86)     $10.62   12.11%   $533,893     0.90%         5.46%       206%
   0.00         (0.13)      10.27    0.02     115,742     0.91+         6.08+       173
   0.00         (0.78)      10.62   11.26     186,932     1.65          4.74        206
   0.00         (0.12)      10.27   (0.10)     74,130     1.67+         5.28+       173
   0.00         (0.79)      10.62   11.28     405,037     1.65          4.83        206
   0.00         (0.12)      10.27   (0.11)    329,104     1.67+         5.32+       173
  $0.00        $(0.59)     $ 9.77    4.12%   $    370     0.92%         4.06%       967%
   0.00         (0.08)       9.93    0.15           1     0.90+         6.14+       160
   0.00         (0.52)       9.77    3.50       1,496     1.67          3.32        967
   0.00         (0.06)       9.93   (0.08)        509     1.59+         3.43+       160
   0.00         (0.55)       9.77    3.73         490     1.42          3.56        967
   0.00         (0.06)       9.93   (0.07)        148     1.62+         5.13+       160
  $0.00        $(0.64)     $10.57   19.78%   $  6,161     0.91%         4.49%       177%
   0.00         (0.13)       9.39   (1.72)      1,204     1.12+         6.91+       402
   0.00         (0.56)      10.57   18.85       7,516     1.66          4.64        177
   0.00         (0.10)       9.39   (1.92)        454     1.87+         4.95+       402
   0.00         (0.56)      10.57   18.86       7,258     1.66          4.64        177
   0.00         (0.10)       9.39   (1.83)        275     1.88+         5.52+       402
  $0.00        $(0.90)     $10.74   12.14%   $  9,582     0.95%         5.88%       280%
   0.00         (0.05)      10.41   (1.21)        704     0.97+         4.95+       984
   0.00         (0.81)      10.74   11.29      10,631     1.70          5.13        280
   0.00         (0.04)      10.41   (1.34)      1,221     1.75+         3.73+       984
   0.00         (0.81)      10.74   11.29      17,080     1.70          5.13        280
   0.00         (0.04)      10.41   (1.32)      1,788     1.76+         4.09+       984
  $0.00        $(2.07)     $ 9.92   11.21%   $  6,816     0.95%         5.88%       369%
   0.00         (0.62)      10.84    4.55       7,652     2.05+         5.60+       307
   0.00         (0.31)      10.96   15.01       7,360     1.27(g)       4.88(h)   1,246
   0.00         (1.99)       9.92   10.39       4,473     1.70          5.12        369
   0.00         (0.58)      10.84    4.17       3,925     2.57+         4.22+       307
   0.00         (0.26)      10.96   14.54       3,240     2.49(g)       4.09(h)   1,246
   0.00         (1.99)       9.92   10.39       6,096     1.70          5.12        369
   0.00         (0.58)      10.84    4.17       5,323     2.43+         4.14+       307
   0.00         (0.26)      10.96   14.54       3,459     2.49(g)       4.09(h)   1,246
  $0.00        $(0.59)     $ 9.67    2.84%   $    317     1.26%         6.93%       695%
   0.00         (0.53)       9.67    2.29         304     2.01          6.33        695
   0.00         (0.53)       9.67    2.29         136     2.01          6.11        695
  $0.00        $(2.47)     $14.06   47.07%   $ 62,970     1.05%        13.34%        30%
   0.00         (0.15)      11.46   (2.59)      5,790     1.10+       (10.69)+       47
   0.00         (2.39)      14.01   46.11      99,039     1.80         12.60         30
   0.00         (0.14)      11.44   (2.81)      8,281     1.88+       (15.13)+       47
   0.00         (2.41)      14.03   46.38      96,960     1.55         12.85         30
   0.00         (0.14)      11.45   (2.71)     11,254     1.65+       (12.79)+       47
</TABLE>
- -------
 +Annualized.
(g)The Ratio of Expenses to Average Net Assets without the waiver would have
been 1.57%.
(h)The Ratio of Net Investment Income to Average Net Assets without the waiver
would have been 4.58%.
                                                                    Prospectus
                                                                              11
<PAGE>
 
            Investment Objectives and Policies
            The investment objective and general investment policies of each
            Fund are described below. There can be no assurance that the in-
            vestment objective of any Fund will be achieved. For temporary,
            defensive or emergency purposes, a Fund may invest without limit
            in U.S. debt securities, including short-term money market securi-
            ties, when in the opinion of the Adviser it is appropriate to do
            so. It is impossible to predict for how long such alternative
            strategies will be utilized. The value of all securities and other
            instruments held by the Funds will vary from time to time in re-
            sponse to a wide variety of market factors. Consequently, the net
            asset value per share of each Fund will vary, except that the
            Money Market Fund will attempt to maintain a net asset value of
            $1.00 per share, although there can be no assurance that the Fund
            will be successful in doing so.
               The investment objective of the Global Bond Fund II described
            in this Prospectus may be changed by the Board of Trustees without
            shareholder approval. The investment objective of each other Fund
            is fundamental and may not be changed without shareholder approval
            by vote of a majority of the outstanding shares of that Fund. If
            there is a change in a Fund's investment objective, including a
            change approved by a shareholder vote, shareholders should con-
            sider whether the Fund remains an appropriate investment in light
            of their then current financial position and needs.
               Specific portfolio securities eligible for purchase by the
            Funds, investment techniques that may be used by the Funds, and
            the risks associated with these securities and techniques are de-
            scribed more fully under "Characteristics and Risks of Securities
            and Investment Techniques" in this Prospectus and "Investment Ob-
            jectives and Policies" in the Statement of Additional Information.
 
 
FIXED       With the exception of the Strategic Balanced and StocksPLUS Funds,
INCOME FUND each remaining Fund (together, the "Fixed Income Funds") differs
DESCRIPTIONSfrom the others primarily in the length of the Fund's duration or
            the proportion of its investments in certain types of fixed income
            securities. For a discussion of the concept of duration, see "Ap-
            pendix A--Description of Duration."
               The investment objective of the Money Market and Short-Term
            Funds is to seek to obtain maximum current income consistent with
            preservation of capital and daily liquidity. The Money Market Fund
            also attempts to maintain a stable net asset value of $1.00 per
            share, although there can be no assurance that it will be success-
            ful in doing so. The investment objective of the Real Return Bond
            Fund is to seek to realize maximum real return, consistent with
            the preservation of real capital and prudent investment manage-
            ment. For a discussion of "real return," see "Total Return and
            Real Return," below. The investment objective of the Municipal
            Bond Fund is to seek high current income exempt from federal in-
            come tax, consistent with preservation of capital. Capital appre-
            ciation is a secondary objective of the Municipal Bond Fund. The
            investment objective of the Global Bond Fund II is to seek maximum
            total return, consistent with the preservation of capital. Each of
            the remaining Fixed Income Funds seeks to maximize total return,
            consistent with preservation of capital and prudent investment
            management.
               In selecting securities for each Fixed Income Fund, the Adviser
            utilizes economic forecasting, interest rate anticipation, credit
            and call risk analysis, foreign currency exchange rate forecast-
            ing, and other security selection techniques. The proportion of
            each Fund's assets committed to investment in securities with par-
            ticular characteristics (such as maturity, type and coupon rate)
            will vary based on the Adviser's outlook for the U.S. and foreign
            economies, the financial markets, and other factors.
               Each of the Fixed Income Funds will invest at least 65% of its
            assets in the following types of securities, which, unless specif-
            ically provided otherwise in the descriptions of the Funds that
            follow, may be issued by domestic or foreign entities and denomi-
            nated in U.S. dollars or foreign currencies: securities issued or
            guaranteed by the U.S. Government, its agencies or instrumentali-
            ties ("U.S. Government securities"); corporate debt securities,
            including convertible securities and corporate commercial paper;
            mortgage-backed and other asset-backed securities; inflation-in-
            dexed bonds issued by both governments and corporations; struc-
            tured notes, including hybrid or "indexed" securities, catastrophe
            bonds, and loan participations; delayed funding loans and revol-
            ving credit facilities; bank certificates of deposit, fixed time
            deposits and bankers' acceptances; repurchase agreements and re-
            verse repurchase agreements; debt securities issued by states or
            local governments and their agencies, authorities and other in-
            strumentalities; obligations of foreign govern-
 
12
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            ments or their subdivisions, agencies and instrumentalities; and
            obligations of international agencies or supranational entities.
            Fixed income securities may have fixed, variable, or floating
            rates of interest, including rates of interest that vary inversely
            at a multiple of a designated or floating rate, or that vary ac-
            cording to changes in relative values of currencies. Each of the
            Fixed Income Funds may hold different percentages of its assets in
            these various types of securities, and each Fund, except the Money
            Market Fund and the Municipal Bond Fund, may invest all of its as-
            sets in derivative instruments or in mortgage- or asset-backed se-
            curities. Each of the Fixed Income Funds, except the Money Market
            Fund, may adhere to its investment policy by entering into a se-
            ries of purchase and sale contracts or utilizing other investment
            techniques by which it may obtain market exposure to the securi-
            ties in which it primarily invests.
               In addition, each of the Fixed Income Funds may lend its port-
            folio securities to brokers, dealers and other financial institu-
            tions in order to earn income. Each of the Fixed Income Funds may
            purchase and sell options and futures subject to the limits dis-
            cussed below, engage in credit spread trades and enter into for-
            ward foreign currency contracts.
               Each of the Real Return Bond, Global Bond II, Foreign Bond, and
            Emerging Markets Bond Funds will normally invest at least 80% of
            its total assets in "bonds." For this purpose, each of these Funds
            considers the various types of debt or fixed income securities in
            which it invests, as specifically described elsewhere in this Pro-
            spectus, to be "bonds" as referenced in that Fund's name. The use
            of this name is not meant to restrict a Fund's investment to the
            narrow category of debt securities that are formally called
            "bonds."
               As a non-fundamental, operating policy, the Adviser intends to
            use foreign currency-related derivative instruments (currency
            futures and related options, currency options, forward contracts
            and swap agreements) in an effort to hedge foreign currency risk
            with respect to at least 75% of the assets of the Fixed Income
            Funds (other than the Emerging Markets Bond Fund) denominated in
            currencies other than the U.S. dollar. There can be no assurance
            that the Adviser will be successful in doing so. The active use of
            currency derivatives involves transaction costs which may ad-
            versely effect yield and return.
 
            The compositions of the Fixed Income Funds differ as follows:
 
            MONEY MARKET FUND seeks maximum current income consistent with the
            preservation of capital and daily liquidity. It attempts to
            achieve this objective by investing at least 95% of its total as-
            sets, measured at the time of investment, in a diversified portfo-
            lio of the highest quality money market securities. The Fund may
            also invest up to 5% of its total assets, measured at the time of
            investment, in money market securities that are in the second-
            highest rating category for short-term obligations. The Fund's in-
            vestments in securities will be limited to U.S. dollar-denominated
            securities that mature in 397 days or less from the date of pur-
            chase. The dollar-weighted average portfolio maturity of the Fund
            will not exceed 90 days. The Fund may invest in the following: ob-
            ligations of the U.S. Government (including its agencies and in-
            strumentalities); short-term corporate debt securities of domestic
            and foreign corporations; obligations of domestic and foreign com-
            mercial banks, savings banks, and savings and loan associations;
            and commercial paper. The Fund may invest more than 25% of its to-
            tal assets in securities or obligations issued by U.S. banks.
               The Fund may invest only in securities that comply with the
            quality, maturity and diversification requirements of Rule 2a-7
            under the Investment Company Act of 1940, which regulates money
            market funds.
 
            SHORT-TERM FUND invests in a diversified portfolio of fixed income
            securities of varying maturities. The average portfolio duration
            of this Fund will normally not exceed one year. The Fund may in-
            vest up to 10% of its assets in fixed income securities that are
            rated below investment grade (rated below Baa by Moody's Investors
            Service, Inc. ("Moody's") or BBB by Standard and Poor's Ratings
            Services ("S&P")) but rated B or higher by Moody's or S&P (or, if
            unrated, determined by the Adviser to be of comparable quality).
            For information on the risks associated with investments in secu-
            rities rated below investment grade, see "Appendix B--Description
            of Securities Ratings." The Fund may invest up to 5% of its assets
            in securities denominated in foreign currencies, and may invest
            beyond this limit in U.S. dollar-denominated securities of foreign
            issuers.
                                                                    Prospectus
                                                                              13
<PAGE>
 
 
            LOW DURATION FUND invests in a diversified portfolio of fixed in-
            come securities of varying maturities. The average portfolio dura-
            tion of this Fund will normally vary within a one- to three-year
            time frame based on the Adviser's forecast for interest rates. The
            Fund may invest up to 10% of its assets in fixed income securities
            that are rated below investment grade but rated B or higher by
            Moody's or S&P (or, if unrated, determined by the Adviser to be of
            comparable quality). For information on the risks associated with
            investments in securities rated below investment grade, see "Ap-
            pendix B--Description of Securities Ratings." The Fund may invest
            up to 20% of its assets in securities denominated in foreign cur-
            rencies, and may invest beyond this limit in U.S. dollar-denomi-
            nated securities of foreign issuers. The total rate of return for
            this Fund is expected to exhibit less volatility than that of the
            Total Return Fund because its duration will be shorter.
 
            REAL RETURN BOND FUND invests under normal circumstances at least
            65% of its total assets in inflation-indexed bonds issued by U.S.
            and foreign governments, their agencies or instrumentalities. The
            Fund may invest up to 10% of its assets in fixed income securities
            that are rated below investment grade but rated B or higher by
            Moody's or S&P (or, if unrated, determined by the Adviser to be of
            comparable quality).The Fund may invest up to 35% of its assets in
            other types of fixed income instruments, including securities de-
            nominated in foreign currencies, (and the Fund may also invest be-
            yond this limit in U.S. dollar-denominated securities of foreign
            issuers).
               Inflation-indexed bonds are fixed income securities whose prin-
            cipal value is periodically adjusted according to the rate of in-
            flation. Such bonds generally are issued at an interest rate lower
            than non-inflation related bonds, but are expected to retain their
            value against inflation over time. For a more complete discussion
            of inflation-indexed bonds, including the risks associated with
            investing in such securities, see "Characteristics and Risks of
            Securities and Investment Techniques--Inflation-Indexed Bonds."
            See "Taxes" for information about the possible tax consequences of
            investing in the Fund and in inflation-indexed bonds.
               In managing fixed income securities, one of the principal tools
            generally used by the Adviser is "duration," which is a measure of
            the expected life of a fixed income security on a present value
            basis, incorporating a bond's yield, coupon interest payments, fi-
            nal maturity and call features. See "Appendix A--Description of
            Duration." Because of the unique features of inflation-indexed
            bonds, the Adviser utilizes a modified form of duration for the
            Real Return Bond Fund ("modified real duration") which measures
            price changes in such bonds as a result of changes in real, rather
            than nominal, interest rates. Although there is no limit on the
            modified real duration of the Real Return Bond Fund, it is ex-
            pected that the average modified real duration of the Fund will
            normally vary approximately within the range of the average modi-
            fied real duration of all inflation-indexed bonds issued by the
            U.S. Treasury in the aggregate.
 
            TOTAL RETURN FUND invests under normal circumstances at least 65%
            of its assets in a diversified portfolio of fixed income securi-
            ties of varying maturities. The average portfolio duration of this
            Fund will normally vary within a three- to six-year time frame
            based on the Adviser's forecast for interest rates. The Fund may
            invest up to 10% of its assets in fixed income securities that are
            rated below investment grade but rated B or higher by Moody's or
            S&P (or, if unrated, determined by the Adviser to be of comparable
            quality). For information on the risks associated with investments
            in securities rated below investment grade, see "Appendix B--De-
            scription of Securities Ratings." The Fund may also invest up to
            20% of its assets in securities denominated in foreign currencies,
            and may invest beyond this limit in U.S. dollar-denominated secu-
            rities of foreign issuers. Portfolio holdings will be concentrated
            in areas of the bond market (based on quality, sector, coupon or
            maturity) which the Adviser believes to be relatively undervalued.
            The total rate of return for this Fund is expected to exhibit less
            volatility than that of the Long-Term U.S. Government Fund because
            its duration will normally be shorter.
 
            HIGH YIELD FUND invests under normal circumstances at least 65% of
            its assets in a diversified portfolio of fixed income securities
            rated lower than Baa by Moody's or lower than BBB by S&P but rated
            at least B by Moody's or S&P (or, if unrated, determined by the
            Adviser to be of comparable quality). The remainder of the Fund's
            assets may be invested in investment grade fixed income securities
            (i.e., securities rated at least Baa by Moody's or BBB by S&P, or,
            if unrated,
 
14
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            deemed by the Adviser to be of comparable quality). The average
            portfolio duration of this Fund will normally vary within a two-
            to six-year time frame depending on the Adviser's view of the po-
            tential for total return offered by a particular duration strate-
            gy. The Fund may invest in securities of foreign issuers, but only
            those that are U.S. dollar-denominated. The Fund may also engage
            in hedging strategies involving equity options.
               Investments in high yield securities, while generally providing
            greater potential opportunity for capital appreciation and higher
            yields than investments in higher rated securities, also entail
            greater risk, including the possibility of default or bankruptcy
            of the issuer of such securities. Risk of default or bankruptcy
            may be greater in periods of economic uncertainty or recession, as
            the issuers of high yield securities may be less able to withstand
            general economic downturns. The Adviser seeks to reduce risk
            through diversification, credit analysis and attention to current
            developments and trends in both the economy and financial markets.
            The value of all fixed income securities, including those held by
            the Fund, can be expected to change inversely with interest rates.
            Securities rated below investment grade may sometimes be referred
            to as "junk bonds." For a further discussion of the special risks
            of investing in lower rated securities, see "Characteristics and
            Risks of Securities and Investment Techniques--High Yield Securi-
            ties ("Junk Bonds")."
 
            MUNICIPAL BOND FUND seeks high current income exempt from federal
            income tax, consistent with preservation of capital. Capital ap-
            preciation is a secondary objective. The Fund seeks its objectives
            by investing in debt securities whose interest is, in the opinion
            of bond counsel for the issuer at the time of issuance, exempt
            from federal income tax ("Municipal Bonds"). Municipal Bonds gen-
            erally are issued by states and local governments and their agen-
            cies, authorities and other instrumentalities. It is a policy of
            the Fund that, under normal market conditions, at least 80% of its
            net assets will be invested in Municipal Bonds. The Fund may in-
            vest up to 20% of its net assets in U.S. Government securities,
            money market instruments and/or "private activity" bonds. Under
            normal circumstances, the average portfolio duration of the Munic-
            ipal Bond Fund will vary within a three- to ten-year time frame,
            based on the Adviser's forecast for interest rates.
               The Fund may invest up to 10% of its net assets in Municipal
            Bonds or "private activity" bonds which are rated below Baa by
            Moody's or BBB by S&P but which are rated at least Ba by Moody's
            or BB by S&P (or, if unrated, determined by the Adviser to be of
            comparable quality). For information on the risks associated with
            investments in securities rated below investment grade, see "Ap-
            pendix B--Description of Securities Ratings."
 
            LONG-TERM U.S. GOVERNMENT FUND invests in a diversified portfolio
            of primarily U.S. Government securities, which may be represented
            by futures contracts (including related options) with respect to
            such securities, and options on such securities, when the Adviser
            deems it appropriate to do so. The Fund will normally have a mini-
            mum average portfolio duration of eight years. For point of refer-
            ence, the dollar-weighted average portfolio maturity of the Fund
            is normally expected to be more than ten years. The total rate of
            return is expected to exhibit more volatility than that of the
            other Fixed Income Funds due to the greater investment risk nor-
            mally associated with longer duration investments. The Long-Term
            U.S. Government Fund's investments in fixed income securities are
            limited to those of U.S. dollar-denominated securities of domestic
            (U.S.) issuers that are rated at least A by Moody's or S&P (or, if
            unrated, determined by the Adviser to be of comparable quality).
            In addition, the Fund will not acquire a security if, as a result,
            more than 10% of the Fund's total assets would be invested in se-
            curities rated below Aa by Moody's or below AA by S&P, or if more
            than 25% of the Fund's total assets would be invested in securi-
            ties rated Aa by Moody's or AA by S&P.
 
            GLOBAL BOND FUND II invests in a portfolio of fixed income securi-
            ties denominated in major currencies, baskets of foreign curren-
            cies (such as the ECU), and the U.S. dollar. Under normal circum-
            stances, at least 65% of the Fund's assets will be invested in
            fixed income securities of issuers located in at least three coun-
            tries (one of which may be the United States), which may be repre-
            sented by futures contracts (including related options) with re-
            spect to such securities, and options on such securities, when the
            Adviser deems it appropriate to do so. Depending on the Adviser's
            current opinion as to the proper allocation of assets among domes-
            tic and foreign issuers, investments in the securities of issuers
            located
 
                                                                             15
                                                                    Prospectus
<PAGE>
 
            outside the United States will normally vary between 25% and 75%
            of the Fund's assets. The Fund may invest up to 10% of its assets
            in fixed income securities that are rated below investment grade
            but rated B or higher by Moody's or S&P (or, if unrated, deter-
            mined by the Adviser to be of comparable quality). For information
            on the risks associated with investments in securities rated below
            investment grade, see "Appendix B--Description of Securities Rat-
            ings." The average portfolio duration of this Fund will normally
            vary within a three- to seven-year time frame.
              The Foreign Bond Fund differs from the Global Bond Fund II pri-
            marily in the extent to which assets are invested in the securi-
            ties of issuers located outside the United States. The Adviser
            will select these Funds' foreign country and currency compositions
            based on an evaluation of relative interest rates, exchange rates,
            monetary and fiscal policies, trade and current account balances,
            and any other specific factors the Adviser believes to be rele-
            vant.
 
            FOREIGN BOND FUND invests in a portfolio of fixed income securi-
            ties primarily denominated in major foreign currencies and baskets
            of foreign currencies (such as the European Currency Unit, or
            "ECU"). The Adviser will invest the assets of the Fund in a number
            of international bond markets so that, under normal circumstances,
            the Fund will invest at least 85% of its assets in securities of
            issuers located outside the United States, representing at least
            three foreign countries, which may be represented by futures con-
            tracts (including related options) with respect to such securi-
            ties, and options on such securities, when the Adviser deems it
            appropriate to do so. The Fund may invest up to 10% of its assets
            in fixed income securities that are rated below investment grade
            but rated B or higher by Moody's or S&P (or, if unrated, deter-
            mined by the Adviser to be of comparable quality). Securities
            rated below investment grade may sometimes be referred to as "junk
            bonds." For information on the risks associated with investments
            in securities rated below investment grade, see "Appendix B--De-
            scription of Securities Ratings." The average portfolio duration
            of this Fund will normally vary within a three- to seven-year time
            frame.
 
            EMERGING MARKETS BOND FUND invests in a portfolio of fixed income
            securities denominated in foreign currencies and the U.S. dollar.
            Under normal market conditions, the Fund will invest at least 80%
            of its assets in fixed income securities of issuers that are eco-
            nomically tied to countries with emerging securities markets. The
            Fund may invest up to 20% of its assets in other types of fixed
            income instruments, including securities of issuers located in, or
            securities denominated in currencies of, countries with developed
            foreign securities markets. The Fund also may invest up to 10% of
            its assets in shares of investment companies that invest primarily
            in emerging market debt securities. The average portfolio duration
            of the Fund will vary based on the Adviser's view of the potential
            for total return offered by a particular duration strategy and,
            under normal market conditions, is not expected to exceed eight
            years.
               The Adviser has broad discretion to identify and invest in
            countries that it considers to qualify as emerging securities mar-
            kets. However, the Adviser generally considers an emerging securi-
            ties market to be one located in any country that is defined as an
            emerging or developing economy by any of the following: the Inter-
            national Bank for Reconstruction and Development (i.e., the World
            Bank), including its various offshoots, such as the International
            Finance Corporation, or the United Nations or its authorities. The
            Fund considers an issuer to be economically tied to a country if
            (1) the issuer is organized under the laws of, or maintains its
            principal place of business in, the country, (2) its securities
            are principally traded in the country's securities markets, or (3)
            the issuer derived at least half of its revenues or profits from
            goods produced or sold, investments made, or services performed in
            the country, or has at least half of its assets in that country.
               The Fund emphasizes countries with relatively low gross na-
            tional product per capita and with the potential for rapid eco-
            nomic growth. The Adviser will select the Fund's country and cur-
            rency composition based on its evaluation of relative interest
            rates, inflation rates, exchange rates, monetary and fiscal poli-
            cies, trade and current account balances, and any other specific
            factors the Adviser believes to be relevant. The Fund likely will
            concentrate its investments in Asia, Africa, the Middle East,
            Latin America and the developing countries of Europe. Accordingly,
            the Fund will be particularly susceptible to the effects of polit-
            ical and economic developments in these regions. This effect may
            be exacerbated by a relative scarcity of issuers in certain of
            these markets, which may result in the Fund being highly
 
16
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            concentrated in a small number of issuers. For a further discus-
            sion of the special risks of investing in foreign and emerging
            market countries, see "Characteristics and Risks of Securities and
            Investment Techniques--Foreign Securities."
               The Fund's investments in emerging market fixed income securi-
            ties may be represented by futures contracts (including related
            options) with respect to such securities, options on such securi-
            ties, equity securities (including common stocks) upon the conver-
            sion of convertible securities, or securities the return on which
            is derived primarily from emerging securities markets, when the
            Adviser deems it appropriate to do so.
               The Fund may invest substantially all of its assets in securi-
            ties rated below investment grade but rated B or higher by Moody's
            or S&P (or, if unrated, determined by the Adviser to be of compa-
            rable quality). Such securities are sometimes referred to as "junk
            bonds." While these securities generally provide greater potential
            opportunity for capital appreciation and higher yields than in-
            vestments in higher rated securities, they also entail greater
            risk, including the possibility of default or bankruptcy of the
            issuer of the securities. Risk of default or bankruptcy may be
            greater in periods of economic uncertainty or recession, as the
            issuers may be less able to withstand general economic downturns
            affecting the regions in which the Fund invests. The Adviser seeks
            to reduce risk through diversification, credit analysis and atten-
            tion to current developments and trends in emerging market econo-
            mies and markets. The value of all fixed income securities, in-
            cluding those held by the Fund, can be expected to change in-
            versely with interest rates. For a further discussion of the spe-
            cial risks of investing in lower rated securities, see "Character-
            istics and Risks of Securities and Investment Techniques--High
            Yield Securities ("Junk Bonds")."
 
 
STOCK AND   STRATEGIC BALANCED FUND has as its investment objective the maxim-
BONDFUND    ization of total return, consistent with preservation of capital
DESCRIPTION and prudent investment management. In seeking to achieve this ob-
            jective, the Fund invests in the securities eligible for purchase
            by the StocksPLUS and Total Return Funds. The percentage of the
            Fund's assets allocated to equity or fixed income exposure will
            vary in accordance with an asset allocation methodology developed
            by theAdviser. The methodology builds upon the Adviser's long-
            standing process of economic forecasting of business cycle stages
            by applying to this process a disciplined asset allocation model
            which employs certain statistical variance techniques. Depending
            on the outcome of this asset allocation methodology, the Fund's
            equity exposure will vary between 45% and 75% of its total assets,
            and its fixed income exposure will vary between 25% and 55%. There
            can be no assurance that the Adviser's asset allocation methodol-
            ogy will be successful.
               Class A, Class B and Class C shares of the Strategic Balanced
            Fund are not offered as of the date of this Prospectus; however,
            investment opportunities in this Fund may be available in the
            future.
 
 
STOCK FUND  STOCKSPLUS FUND, as its investment objective, seeks to achieve to-
DESCRIPTION tal return which exceeds the total return performance of the Stan-
            dard & Poor's 500 Composite Stock Price Index ("S&P 500").
            StocksPLUS is the name of a proprietary portfolio management
            strategy which utilizes S&P 500 derivatives in addition to or in
            place of S&P 500 stocks to equal or exceed the performance of the
            S&P 500. The Adviser expects that under normal market conditions,
            the Fund will invest substantially all of its assets in S&P 500
            derivatives, backed by a portfolio of fixed income securities. The
            Adviser will actively manage the fixed income assets serving as
            cover for derivatives, as well as any other fixed income assets
            held by the Fund, with a view toward enhancing the Fund's total
            return investment performance, subject to an overall portfolio du-
            ration which is normally not expected to exceed one year. See "Ap-
            pendix A--Description of Duration."
               The S&P 500 is composed of 500 selected common stocks, most of
            which are listed on the New York Stock Exchange. S&P chooses the
            stocks to be included in the S&P 500 solely on a statistical ba-
            sis. The weightings of stocks in the index are based on each
            stock's relative total market value, that is, its market price per
            share times the number of shares outstanding. Stocks represented
            currently in the S&P 500 represent approximately two-thirds of the
            total market value of all U.S. common stocks. The Fund is neither
            sponsored by nor affiliated with S&P. The Fund will seek to remain
            invested in S&P 500 derivatives or S&P 500 stocks even when the
            S&P 500 is declining.
                                                                    Prospectus
                                                                              17
<PAGE>
 
               When S&P 500 derivatives appear to be overvalued relative to
            the S&P 500, the Fund may invest up to 100% of its assets in a
            "basket" of S&P 500 stocks. The composition of this basket will be
            determined by standard statistical techniques that analyze the
            historical correlation between the return of every stock currently
            in the S&P 500 and the return on the S&P 500 itself. The Adviser
            may employ fundamental stock analysis only to choose among stocks
            that have already satisfied the statistical correlation tests.
            Stocks chosen for the Fund are not limited to those with any par-
            ticular weighting in the S&P 500.
               Positions in S&P 500 futures and options on futures will be en-
            tered into only to the extent they constitute permissible posi-
            tions for the Fund according to applicable rules of the Commodity
            Futures Trading Commission ("CFTC"). From time to time, the Ad-
            viser may be constrained in its ability to use S&P 500 derivatives
            either by requirements of the Internal Revenue Code or by an unan-
            ticipated inability to close out positions when it would be most
            advantageous to do so. A large number of investors use S&P 500 de-
            rivatives for both hedging and speculative purposes, and although
            generally this helps guarantee a liquid market in those instru-
            ments, at times liquidity may be limited. For more information
            about S&P 500 derivatives, see "Characteristics and Risks of Secu-
            rities and Investment Techniques--Derivative Instruments."
               Assets of the StocksPLUS Fund not invested in equity securities
            may be invested in securities eligible for purchase by the Fixed
            Income Funds. The Fund may invest up to 10% of its assets in fixed
            income securities that are below "investment grade," i.e., rated
            below Baa by Moody's or BBB by S&P, but at least B (or, if
            unrated, determined by the Adviser to be of comparable quality).
            In addition, the StocksPLUS Fund may lend its portfolio securities
            to brokers, dealers and other financial institutions in order to
            earn income. The Fund may also invest all of its assets in deriva-
            tive instruments, as described under "Characteristics of Securi-
            ties and Investment Techniques--Derivative Instruments." In addi-
            tion, the Fund may invest up to 20% of its assets in securities of
            foreign issuers, may purchase and sell options and futures on for-
            eign currencies, and may enter into forward foreign currency con-
            tracts.
               To the extent that the Fund invests in S&P 500 derivatives
            backed by a portfolio of fixed income securities, under certain
            conditions, generally in a market where the value of both S&P 500
            derivatives and fixed income securities are declining, the Fund
            may experience greater losses than would be the case if it were to
            invest directly in a portfolio of S&P 500 stocks.
 
 
TOTAL       The "total return" sought by certain of the Funds will consist of
RETURN AND  interest and dividends from underlying securities, capital appre-
REAL RETURN ciation reflected in unrealized increases in value of portfolio
            securities (realized by the shareholder only upon selling shares),
            or realized from the purchase and sale of securities and use of
            futures and options, or gains from favorable changes in foreign
            currency exchange rates. Generally, over the long term, the total
            return obtained by a portfolio investing primarily in fixed income
            securities is not expected to be as great as that obtained by a
            portfolio that invests primarily in equity securities. At the same
            time, the market risk and price volatility of a fixed income port-
            folio is expected to be less than that of an equity portfolio, so
            that a fixed income portfolio is generally considered to be a more
            conservative investment. The change in market value of fixed in-
            come securities (and therefore their capital appreciation or de-
            preciation) is largely a function of changes in the current level
            of interest rates. Generally, when interest rates are falling, a
            portfolio with a shorter duration will not generate as high a
            level of total return as a portfolio with a longer duration. Con-
            versely, when interest rates are rising, a portfolio with a
            shorter duration will generally outperform longer duration portfo-
            lios. When interest rates are flat, shorter duration portfolios
            generally will not generate as high a level of total return as
            longer duration portfolios (assuming that long-term interest rates
            are higher than short-term rates, which is commonly the case).
            With respect to the composition of any fixed income portfolio, the
            longer the duration of the portfolio, the greater the anticipated
            potential for total return, with, however, greater attendant mar-
            ket risk and price volatility than for a portfolio with a shorter
            duration. The market value of fixed income securities denominated
            in currencies other than the U.S. dollar also may be affected by
            movements in foreign currency exchange rates.
 
18
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               The change in market value of equity securities (and therefore
            their capital appreciation or depreciation) may depend upon a num-
            ber of factors, including: conditions in the securities markets,
            the business success of the security's issuer, changing interest
            rates, real or perceived economic and competitive industry condi-
            tions, and foreign currency exchange rates. Historically, the to-
            tal return performance of equity-oriented portfolios has generally
            been greater over the long term than fixed income portfolios. How-
            ever, the market risk and price volatility of an equity portfolio
            is generally greater than that of a fixed income portfolio, and is
            generally considered to be a more aggressive investment.
               "Real Return," or "Inflation Adjusted Return," as referenced in
            the name and investment objective of the Real Return Bond Fund, is
            a measure of the change in purchasing power of money invested in a
            particular instrument after adjusting for inflation. An investment
            in a security generating a high nominal return (such as a typical
            U.S. Government Treasury bond) may not generate a high real return
            once inflation is considered. For example, an instrument generat-
            ing a 9% nominal return at a time when inflation is 6% has a real
            return of approximately 3%; that is, the purchasing power of the
            money invested in that instrument would only increase by approxi-
            mately 3%. On the other hand, an inflation-indexed instrument gen-
            erating a 5% real return would generate a 5% increase in purchas-
            ing power regardless of the rate of inflation. As stated above,
            the investment objective of the Fund is to seek to achieve maximum
            real return. The total return (not adjusted for inflation) at-
            tained by this Fund may be less than the total return attained by
            other of the Funds that do not invest primarily in inflation-in-
            dexed securities.
               In the case of inflation-indexed bonds, changes in market value
            are tied to the relationship between nominal interest rates and
            the rate of inflation. If inflation were to rise at a faster rate
            than nominal interest rates, real interest rates might decline,
            leading to an increase in value of inflation-indexed bonds. In
            contrast, if nominal interest rates increase at a faster rate than
            inflation, real interest rates might increase, leading to a de-
            crease in value of inflation-indexed bonds.
 
            Investment Risks and Considerations
 
            The following are some of the principal risks of investing in the
            Funds. Investors should read this Prospectus carefully for a more
            complete discussion of the risks relating to an investment in the
            Funds. The net asset value per share of any Fund may be less at
            the time of redemption than it was at the time of investment. Gen-
            erally, the value of fixed income securities can be expected to
            vary inversely with changes in prevailing interest rates, i.e., as
            interest rates rise, market value tends to decrease, and vice
            versa, although this may not be true in the case of inflation-
            indexed bonds. In addition, certain of the Funds may invest in se-
            curities rated lower than Baa by Moody's or S&P. Such securities
            carry a high degree of credit risk and are considered speculative
            by the major rating agencies.
               Certain Funds may invest in securities of foreign issuers,
            which may be subject to additional risk factors, including foreign
            currency and political risks, not applicable to securities of U.S.
            issuers. Certain of the Funds' investment techniques may involve a
            form of borrowing, which may tend to exaggerate the effect on net
            asset value of any increase or decrease in the market value of a
            Fund's portfolio and may require liquidation of portfolio posi-
            tions when it is not advantageous to do so. Certain Funds may sell
            securities short, which exposes the Fund to a risk of loss if the
            value of the security sold short should increase.
               All Funds (except the Money Market Fund) may use derivative in-
            struments, consisting of futures, options, options on futures, and
            swap agreements, for hedging purposes or as part of their invest-
            ment strategies. Use of these instruments may involve certain
            costs and risks, including the risk that a Fund could not close
            out a position when it would be most advantageous to do so, the
            risk of an imperfect correlation between the value of the securi-
            ties being hedged and the value of the particular derivative in-
            strument, and the risk that unexpected changes in interest rates
            may adversely affect the value of a Fund's investments in particu-
            lar derivative instruments. Unless otherwise indicated, all limi-
            tations applicable to Fund investments (as stated in this Prospec-
            tus and in the Statement of Additional Information) apply only at
            the time a transaction is entered into. Any subsequent change in a
            rating assigned by any rating service to a security (or, if
            unrated, deemed to be of comparable quality), or change in the
            percentage of Fund assets invested in certain securities or
 
                                                                             19
                                                                    Prospectus
<PAGE>
 
            other instruments, or change in the average duration of a Fund's
            investment portfolio, resulting from market fluctuations or other
            changes in a Fund's total assets, will not require a Fund to dis-
            pose of an investment until the Adviser determines that is practi-
            cable to sell or close out the investment without undue market or
            tax consequences to the Fund. In the event that ratings services
            assign different ratings to the same security, the Adviser will
            determine which rating it believes best reflects the security's
            quality and risk at that time, which may be the higher of the sev-
            eral assigned ratings.
               Investors should carefully consider the possible tax conse-
            quences from investing in the Real Return Bond Fund. The Fund in-
            vests primarily in securities that for tax purposes may be consid-
            ered to have been issued originally at a discount. Accordingly,
            the Fund may be required to make annual distributions to share-
            holders in excess of the cash received by the Fund in a given pe-
            riod from those investments. See "Characteristics and Risks of Se-
            curities and Investment Techniques--Inflation-Indexed Bonds" and
            "Taxes" for additional information.
               The Real Return Bond, Global Bond II, Foreign Bond and Emerging
            Markets Bond Funds are "non-diversified" for purposes of the In-
            vestment Company Act of 1940 ("1940 Act"), meaning that they may
            invest a greater percentage of their assets in the securities of
            one issuer than the other Funds. The Funds are still, however,
            subject to diversification requirements imposed by the Internal
            Revenue Code of 1986, as amended, which means that as of the end
            of each calendar quarter, a Fund may have no more than 25% of its
            assets invested in the securities of a single issuer, and may,
            with respect to 50% of its assets, have no more than 5% of its as-
            sets invested in the securities of a single issuer. As "non-diver-
            sified" portfolios, these Funds may be more susceptible to risks
            associated with a single economic, political or regulatory occur-
            rence than a diversified portfolio might be.
               The Funds offer their shares to both retail and institutional
            investors. Institutional shareholders, some of whom also may be
            investment advisory clients of Pacific Investment Management, may
            hold large positions in certain of the Funds. Such shareholders
            may on occasion make large redemptions of their holdings in the
            Funds to meet their liquidity needs, in connection with strategic
            adjustments to their overall portfolio of investments, or for
            other purposes. Large redemptions from some Funds could require
            the Adviser to liquidate portfolio positions when it is not most
            desirable to do so. Liquidation of portfolio holdings also may
            cause a Fund to realize taxable capital gains.
 
            Characteristics and Risks of
            Securities and Investment Techniques
 
            The following describes in greater detail different types of secu-
            rities and investment techniques used by the individual Funds, and
            discusses certain concepts relevant to the investment policies of
            the Funds. Additional information about the Funds' investments and
            investment practices may be found in the Statement of Additional
            Information.
 
 
U.S.        U.S. Government securities are obligations of, or guaranteed by,
GOVERNMENT  the U.S. Government, its agencies or instrumentalities. The U.S.
SECURITIES  Government does not guarantee the net asset value of the Funds'
            shares. Some U.S. Government securities, such as Treasury bills,
            notes and bonds, and securities guaranteed by the Government Na-
            tional Mortgage Association ("GNMA"), are supported by the full
            faith and credit of the United States; others, such as those of
            the Federal Home Loan Banks, are supported by the right of the is-
            suer to borrow from the U.S. Treasury; others, such as those of
            the Federal National Mortgage Association ("FNMA"), are supported
            by the discretionary authority of the U.S. Government to purchase
            the agency's obligations; and still others, such as those of the
            Student Loan Marketing Association, are supported only by the
            credit of the instrumentality. U.S. Government securities include
            securities that have no coupons, or have been stripped of their
            unmatured interest coupons, individual interest coupons from such
            securities that trade separately, and evidences of receipt of such
            securities. Such securities may pay no cash income, and are pur-
            chased at a deep discount from their value at maturity. Because
            interest on zero coupon securities is not distributed on a current
            basis but is, in effect, compounded, zero coupon securities tend
            to be subject to greater market risk than interest-paying securi-
            ties of similar maturities. Custodial receipts issued in connec-
            tion with so-called trademark zero
 
20
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            coupon securities, such as CATs and TIGRs, are not issued by the
            U.S. Treasury, and are therefore not U.S. Government securities,
            although the underlying bond represented by such receipt is a debt
            obligation of the U.S. Treasury. Other zero coupon Treasury secu-
            rities (STRIPs and CUBEs) are direct obligations of the U.S. Gov-
            ernment.
 
 
CORPORATE   Corporate debt securities include corporate bonds, debentures,
DEBT        notes and other similar corporate debt instruments, including con-
SECURITIES  vertible securities. Debt securities may be acquired with warrants
            attached. Corporate income-producing securities may also include
            forms of preferred or preference stock. The rate of interest on a
            corporate debt security may be fixed, floating or variable, and
            may vary inversely with respect to a reference rate. See "Variable
            and Floating Rate Securities" below. The rate of return or return
            of principal on some debt obligations may be linked or indexed to
            the level of exchange rates between the U.S. dollar and a foreign
            currency or currencies.
               Investments in corporate debt securities that are rated below
            investment grade (rated below Baa (Moody's) or BBB (S&P)) are de-
            scribed as "speculative" both by Moody's and S&P. Such securities
            are sometimes referred to as "junk bonds," and may be subject to
            greater market fluctuations, less liquidity and greater risk of
            loss of income or principal, including a greater possibility of
            default or bankruptcy of the issuer of such securities, than are
            more highly rated debt securities. Moody's also describes securi-
            ties rated Baa as having speculative characteristics. The Adviser
            seeks to minimize these risks through diversification, in-depth
            credit analysis and attention to current developments in interest
            rates and market conditions. See "Appendix B--Description of Secu-
            rities Ratings." Investments in high yield securities are dis-
            cussed separately below under "High Yield Securities ("Junk
            Bonds")."
 
 
CONVERTIBLE Each Fund (except the Municipal Bond Fund) may invest in convert-
SECURITIES  ible securities, which may offer higher income than the common
            stocks into which they are convertible. Typically, convertible se-
            curities are callable by the company, which may, in effect, force
            conversion before the holder would otherwise choose.
               The convertible securities in which the Funds may invest con-
            sist of bonds, notes, debentures and preferred stocks which may be
            converted or exchanged at a stated or determinable exchange ratio
            into underlying shares of common stock. A Fund may be required to
            permit the issuer of a convertible security to redeem the securi-
            ty, convert it into the underlying common stock, or sell it to a
            third party. Thus, a Fund may not be able to control whether the
            issuer of a convertible security chooses to convert that security.
            If the issuer chooses to do so, this action could have an adverse
            effect on a Fund's ability to achieve its investment objectives.
               While the Fixed Income Funds intend to invest primarily in
            fixed income securities, each may invest in convertible securities
            or equity securities. While some countries or companies may be re-
            garded as favorable investments, pure fixed income opportunities
            may be unattractive or limited due to insufficient supply, legal
            or technical restrictions. In such cases, a Fund may consider eq-
            uity securities or convertible bonds to gain exposure to such in-
            vestments.
 
 
LOAN
PARTICIPATIONS
AND
ASSIGNMENTS
            Certain Funds may invest in fixed- and floating-rate loans ar-
            ranged through private negotiations between an issuer of debt in-
            struments and one or more financial institutions ("lenders"). Gen-
            erally, the Funds' investments in loans are expected to take the
            form of loan participations and assignments of portions of loans
            from third parties.
               Large loans to corporations or governments may be shared or
            syndicated among several lenders, usually banks. The Funds may
            participate in such syndicates, or can buy part of a loan, becom-
            ing a direct lender. Participations and assignments involve spe-
            cial types of risk, including limited marketability and the risks
            of being a lender. See "Illiquid Securities" for a discussion of
            the limits on a Fund's investments in loan participations and as-
            signments with limited marketability. If a Fund purchases a par-
            ticipation, it may only be able to enforce its rights through the
            lender, and may assume the credit risk of the lender in addition
            to the borrower. In assignments, the Funds' rights against the
            borrower may be more limited than those held by the original lend-
            er.
 
 
DELAYED
FUNDING     The Funds (except the PIMCO Money Market and Municipal Bond Funds)
LOANS AND   may also enter into, or acquire participations in, delayed funding
REVOLVING   loans and revolving credit facilities. Delayed funding loans and
CREDIT      revolving credit facilities are borrowing arrangements in which
FACILITIES  the lender agrees to make loans up to a maximum amount upon demand
            by the
                                                                    Prospectus
                                                                              21
<PAGE>
 
            borrower during a specified term. A revolving credit facility dif-
            fers from a delayed funding loan in that as the borrower repays
            the loan, an amount equal to the repayment may be borrowed again
            during the term of the revolving credit facility. These commit-
            ments may have the effect of requiring a Fund to increase its in-
            vestment in a company at a time when it might not otherwise decide
            to do so (including at a time when the company's financial condi-
            tion makes it unlikely that such amounts will be repaid).
               The Funds may acquire a participation interest in delayed fund-
            ing loans or revolving credit facilities from a bank or other fi-
            nancial institution. See "Loan Participations and Assignments."
            The terms of the participation require the Fund to make a pro rata
            share of all loans extended to the borrower and entitles the Fund
            to a pro rata share of all payments made by the borrower. Delayed
            funding loans and revolving credit facilities usually provide for
            floating or variable rates of interest. To the extent that a Fund
            is committed to advance additional funds, it will at all times
            segregate assets, determined to be liquid by the Adviser in accor-
            dance with procedures established by the Board of Trustees, in an
            amount sufficient to meet such commitments.
 
VARIABLE
AND         Variable and floating rate securities provide for a periodic ad-
FLOATING    justment in the interest rate paid on the obligations. The terms
RATE        of such obligations must provide that interest rates are adjusted
SECURITIES  periodically based upon an interest rate adjustment index as pro-
            vided in the respective obligations. The adjustment intervals may
            be regular, and range from daily up to annually, or may be event
            based, such as based on a change in the prime rate. The Money Mar-
            ket Fund may invest in a variable rate security having a stated
            maturity in excess of 397 calendar days if the interest rate will
            be adjusted, and the Fund may demand payment of principal from the
            issuer, within the period.
               Each of the Fixed Income Funds may invest in floating rate debt
            instruments ("floaters") and (except the Money Market and Munici-
            pal Bond Funds) engage in credit spread trades. The interest rate
            on a floater is a variable rate which is tied to another interest
            rate, such as a money-market index or Treasury bill rate. The in-
            terest rate on a floater resets periodically, typically every six
            months. While, because of the interest rate reset feature, float-
            ers provide a Fund with a certain degree of protection against
            rises in interest rates, a Fund will participate in any declines
            in interest rates as well. A credit spread trade is an investment
            position relating to a difference in the prices or interest rates
            of two securities or currencies, where the value of the investment
            position is determined by movements in the difference between the
            prices or interest rates, as the case may be, of the respective
            securities or currencies.
               Each of the Fixed Income Funds (except the Money Market Fund
            and the Municipal Bond Fund) may also invest in inverse floating
            rate debt instruments ("inverse floaters"). The interest rate on
            an inverse floater resets in the opposite direction from the mar-
            ket rate of interest to which the inverse floater is indexed. An
            inverse floating rate security may exhibit greater price volatil-
            ity than a fixed rate obligation of similar credit quality. The
            Funds have adopted a policy under which no Fund will invest more
            than 5% of its net assets in any combination of inverse floater,
            interest only ("IO"), or principal only ("PO") securities. See
            "Mortgage-Related and Other Asset-Backed Securities" for a discus-
            sion of IOs and POs.
 
 
INFLATION-  Inflation-indexed bonds are fixed income securities whose princi-
INDEXED     pal value is periodically adjusted according to the rate of infla-
BONDS       tion. Two structures are common. The U.S. Treasury and some other
            issuers use a structure that accrues inflation into the principal
            value of the bond. Most other issuers pay out the CPI accruals as
            part of a semiannual coupon.
               Inflation-indexed securities issued by the U.S. Treasury have
            maturities of five, ten or thirty years, although it is possible
            that securities with other maturities will be issued in the fu-
            ture. The U.S. Treasury securities pay interest on a semi-annual
            basis, equal to a fixed percentage of the inflation-adjusted prin-
            cipal amount. For example, if an investor purchased an inflation-
            indexed bond with a par value of $1,000 and a 3% real rate of re-
            turn coupon (payable 1.5% semi-annually), and inflation over the
            first six months were 1%, the mid-year par value of the bond would
            be $1,010 and the first semi-annual interest payment would be
            $15.15 ($1,010 times 1.5%). If inflation during the second half of
            the year resulted in the whole years' inflation equalling 3%, the
            end-of-year par value of the bond would be $1,030 and the second
            semi-annual interest payment would be $15.45 ($1,030 times 1.5%).
 
22
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               If the periodic adjustment rate measuring inflation falls, the
            principal value of inflation-indexed bonds will be adjusted down-
            ward, and consequently the interest payable on these securities
            (calculated with respect to a smaller principal amount) will be
            reduced. Repayment of the original bond principal upon maturity
            (as adjusted for inflation) is guaranteed in the case of U.S.
            Treasury inflation-indexed bonds, even during a period of defla-
            tion. However, the current market value of the bonds is not guar-
            anteed, and will fluctuate. The Funds may also invest in other in-
            flation related bonds which may or may not provide a similar guar-
            antee. If such a guarantee of principal is not provided, the ad-
            justed principal value of the bond repaid at maturity may be less
            than the original principal.
               The value of inflation-indexed bonds is expected to change in
            response to changes in real interest rates. Real interest rates in
            turn are tied to the relationship between nominal interest rates
            and the rate of inflation. Therefore, if inflation were to rise at
            a faster rate than nominal interest rates, real interest rates
            might decline, leading to an increase in value of inflation-in-
            dexed bonds. In contrast, if nominal interest rates increased at a
            faster rate than inflation, real interest rates might rise, lead-
            ing to a decrease in value of inflation-indexed bonds.
               While these securities are expected to be protected from long-
            term inflationary trends, short-term increases in inflation may
            lead to a decline in value. If interest rates rise due to reasons
            other than inflation (for example, due to changes in currency ex-
            change rates), investors in these securities may not be protected
            to the extent that the increase is not reflected in the bond's in-
            flation measure.
               The periodic adjustment of U.S. inflation-indexed bonds is tied
            to the Consumer Price Index for Urban Consumers ("CPI-U"), which
            is calculated monthly by the U.S. Bureau of Labor Statistics. The
            CPI-U is a measurement of changes in the cost of living, made up
            of components such as housing, food, transportation and energy.
            Inflation-indexed bonds issued by a foreign government are gener-
            ally adjusted to reflect a comparable inflation index, calculated
            by that government. There can be no assurance that the CPI-U or
            any foreign inflation index will accurately measure the real rate
            of inflation in the prices of goods and services. Moreover, there
            can be no assurance that the rate of inflation in a foreign coun-
            try will be correlated to the rate of inflation in the United
            States.
               Any increase in the principal amount of an inflation-indexed
            bond will be considered taxable ordinary income, even though in-
            vestors do not receive their principal until maturity. See "Taxes"
            for information about the possible tax consequences of investing
            in the Real Return Bond Fund and in inflation-indexed bonds.
 
MORTGAGE-   Each of the Funds (except the Money Market Fund and the Municipal
RELATED AND Bond Fund) may invest all of its assets in mortgage- or other as-
OTHER       set-backed securities. The value of some mortgage- or asset-backed
ASSET-      securities in which the Funds invest may be particularly sensitive
BACKED      to changes in prevailing interest rates, and, like the other in-
SECURITIES  vestments of the Funds, the ability of a Fund to successfully uti-
            lize these instruments may depend in part upon the ability of the
            Adviser to forecast interest rates and other economic factors cor-
            rectly.
 
            MORTGAGE-PASS-THROUGH SECURITIES are securities representing in-
            terests in "pools" of mortgage loans secured by residential or
            commercial real property in which payments of both interest and
            principal on the securities are generally made monthly, in effect
            "passing through" monthly payments made by the individual borrow-
            ers on the mortgage loans which underlie the securities (net of
            fees paid to the issuer or guarantor of the securities). Early re-
            payment of principal on some mortgage-related securities (arising
            from prepayments of principal due to sale of the underlying prop-
            erty, refinancing, or foreclosure, net of fees and costs which may
            be incurred) may expose a Fund to a lower rate of return upon re-
            investment of principal. Also, if a security subject to prepayment
            has been purchased at a premium, the value of the premium would be
            lost in the event of prepayment. Like other fixed income securi-
            ties, when interest rates rise, the value of a mortgage-related
            security generally will decline; however, when interest rates are
            declining, the value of mortgage-related securities with prepay-
            ment features may not increase as much as other fixed income secu-
            rities. The rate of prepayments on underlying mortgages will af-
            fect the price and volatility of a mortgage-related security, and
            may have the effect of shortening or extending the effective matu-
            rity of the security beyond what was anticipated at the time of
            purchase. To the extent that unanticipated rates of prepayment on
            underlying mortgages increase the effective maturity of a mort-
            gage-related security, the volatility of such security can be ex-
            pected to increase.
                                                                    Prospectus
                                                                              23
<PAGE>
 
               Payment of principal and interest on some mortgage pass-through
            securities (but not the market value of the securities themselves)
            may be guaranteed by the full faith and credit of the U.S. Govern-
            ment (in the case of securities guaranteed by GNMA); or guaranteed
            by agencies or instrumentalities of the U.S. Government (in the
            case of securities guaranteed by FNMA or the Federal Home Loan
            Mortgage Corporation ("FHLMC"), which are supported only by the
            discretionary authority of the U.S. Government to purchase the
            agency's obligations). Mortgage-related securities created by non-
            governmental issuers (such as commercial banks, savings and loan
            institutions, private mortgage insurance companies, mortgage bank-
            ers and other secondary market issuers) may be supported by vari-
            ous forms of insurance or guarantees, including individual loan,
            title, pool and hazard insurance and letters of credit, which may
            be issued by governmental entities, private insurers or the mort-
            gage poolers.
 
            COLLATERALIZED MORTGAGE OBLIGATIONS ("CMOs") are hybrid mortgage-
            related instruments. Interest and pre-paid principal on a CMO are
            paid, in most cases, on a monthly basis. CMOs may be collateral-
            ized by whole mortgage loans but are more typically collateralized
            by portfolios of mortgage pass-through securities guaranteed by
            GNMA, FHLMC, or FNMA. CMOs are structured into multiple classes,
            with each class bearing a different stated maturity. Monthly pay-
            ments of principal, including prepayments, are first returned to
            investors holding the shortest maturity class; investors holding
            the longer maturity classes receive principal only after the first
            class has been retired. CMOs that are issued or guaranteed by the
            U.S. Government or by any of its agencies or instrumentalities
            will be considered U.S. Government securities by the Funds, while
            other CMOs, even if collateralized by U.S. Government securities,
            will have the same status as other privately issued securities for
            purposes of applying a Fund's diversification tests.
 
            COMMERCIAL MORTGAGE-BACKED SECURITIES include securities that re-
            flect an interest in, and are secured by, mortgage loans on com-
            mercial real property. The market for commercial mortgage-backed
            securities developed more recently and in terms of total outstand-
            ing principal amount of issues is relatively small compared to the
            market for residential single-family mortgage-backed securities.
            Many of the risks of investing in commercial mortgage-backed secu-
            rities reflect the risks of investing in the real estate securing
            the underlying mortgage loans. These risks reflect the effects of
            local and other economic conditions on real estate markets, the
            ability of tenants to make loan payments, and the ability of a
            property to attract and retain tenants. Commercial mortgage-backed
            securities may be less liquid and exhibit greater price volatility
            than other types of mortgage-related or asset-backed securities.
 
            MORTGAGE-RELATED SECURITIES include securities other than those
            described above that directly or indirectly represent a participa-
            tion in, or are secured by and payable from, mortgage loans on
            real property, such as mortgage dollar rolls (see "Reverse Repur-
            chase Agreements, Dollar Rolls, and Borrowings"), CMO residuals or
            stripped mortgage-backed securities ("SMBS"), and may be struc-
            tured in classes with rights to receive varying proportions of
            principal and interest.
               A common type of SMBS will have one class receiving some of the
            interest and most of the principal from the mortgage assets, while
            the other class will receive most of the interest and the remain-
            der of the principal. In the most extreme case, one class will re-
            ceive all of the interest (the interest-only, or "IO" class),
            while the other class will receive all of the principal (the prin-
            cipal-only, or "PO" class). The yield to maturity on an IO class
            is extremely sensitive to the rate of principal payments (includ-
            ing prepayments) on the related underlying mortgage assets, and a
            rapid rate of principal payments may have a material adverse ef-
            fect on a Fund's yield to maturity from these securities. The
            Funds have adopted a policy under which no Fund will invest more
            than 5% of its net assets in any combination of IO, PO, or inverse
            floater securities. The Funds may invest in other asset-backed se-
            curities that have been offered to investors. For a discussion of
            the characteristics of some of these instruments, see the State-
            ment of Additional Information.
 
MUNICIPAL
BONDS
            The Municipal Bond Fund invests in Municipal Bonds which are gen-
            erally issued by states and local governments and their agencies,
            authorities and other instrumentalities. The Municipal Bonds which
            the Municipal Bond Fund may purchase include general obligation
            bonds and limited obligation bonds (or revenue bonds), including
            industrial develop-
 
24
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            ment bonds issued pursuant to former federal tax law. General ob-
            ligation bonds are obligations involving the credit of an issuer
            possessing taxing power and are payable from such issuer's general
            revenues and not from any particular source. Limited obligation
            bonds are payable only from the revenues derived from a particular
            facility or class of facilities or, in some cases, from the pro-
            ceeds of a special excise or other specific revenue source. Tax-
            exempt "private activity" bonds and industrial development bonds
            generally are also revenue bonds and thus are not payable from the
            issuer's general revenues. The Municipal Bond Fund may invest in
            Municipal Bonds with credit enhancements such as letters of cred-
            it, municipal bond insurance and Standby Bond Purchase Agreements.
            The Municipal Bond Fund may also invest in municipal lease obliga-
            tions, as well as securities derived from Municipal Bonds, such as
            residual interest bonds and participation interests.
              Municipal Bonds are subject to credit and market risk. Credit
            risk relates to the ability of the issuer to make payments of
            principal and interest. The ability of an issuer to make such pay-
            ments could be affected by litigation, legislation or other polit-
            ical events or the bankruptcy of the issuer. Market risk relates
            to changes in a security's value as a result of changes in inter-
            est rates. Lower rated Municipal Bonds generally provide higher
            yields but are subject to greater credit and market risk than
            higher quality Municipal Bonds.
 
REPURCHASE  For the purpose of achieving income, each of the Funds may enter
AGREEMENTS  into repurchase agreements, which entail the purchase of a portfo-
            lio-eligible security from a bank or broker-dealer that agrees to
            repurchase the security at the Fund's cost plus interest within a
            specified time (normally one day). If the party agreeing to repur-
            chase should default, as a result of bankruptcy or otherwise, the
            Fund will seek to sell the securities which it holds, which action
            could involve procedural costs or delays in addition to a loss on
            the securities if their value should fall below their repurchase
            price. No Fund will invest more than 15% of its net assets (10% in
            the case of the Money Market Fund) (taken at current market value)
            in repurchase agreements maturing in more than seven days.
 
 
REVERSE     A reverse repurchase agreement involves the sale of a security by
REPURCHASE  a Fund and its agreement to repurchase the instrument at a speci-
AGREEMENTS, fied time and price. Under a reverse repurchase agreement, the
DOLLAR      Fund continues to receive any principal and interest payments on
ROLLS, AND  the underlying security during the term of the agreement. The Fund
BORROWINGS  generally will segregate assets determined to be liquid by the Ad-
            viser in accordance with procedures established by the Board of
            Trustees to cover its obligations under reverse repurchase agree-
            ments and, to this extent, a reverse repurchase agreement (or eco-
            nomically similar transaction) will not be considered a "senior
            security" subject to the 300% asset coverage requirements other-
            wise applicable to borrowings by a Fund.
               A Fund may enter into dollar rolls, in which the Fund sells
            mortgage-backed or other securities for delivery in the current
            month and simultaneously contracts to purchase substantially simi-
            lar securities on a specified future date. In the case of dollar
            rolls involving mortgage-backed securities, the mortgage-backed
            securities that are purchased will be of the same type and will
            have the same interest rate as those sold, but will be supported
            by different pools of mortgages. The Fund forgoes principal and
            interest paid during the roll period on the securities sold in a
            dollar roll, but the Fund is compensated by the difference between
            the current sales price and the lower price for the future pur-
            chase as well as by any interest earned on the proceeds of the se-
            curities sold. The Fund also could be compensated through the re-
            ceipt of fee income equivalent to a lower forward price. The Fund
            will segregate assets determined to be liquid by the Adviser in
            accordance with procedures established by the Board of Trustees to
            cover its obligations under dollar rolls.
               To the extent that positions in reverse repurchase agreements,
            dollar rolls or similar transactions are not covered through the
            maintenance of segregated liquid assets at least equal to the
            amount of any forward purchase commitment, such transactions would
            be subject to the Funds' limitations on borrowings, which would
            restrict the aggregate of such transactions (plus any other
            borrowings) to 33 1/3% (for each Fund except the Global Bond
            Fund II) of such Fund's total assets. Apart from such transac-
            tions, a Fund will not borrow money, except for temporary adminis-
            trative purposes. The Global Bond Fund II may not borrow in excess
            of 10% of the value of its total assets and then only from banks
            as a temporary measure to facilitate the meeting of redemption re-
            quests (not for leverage) or for extraordinary or emergency pur-
            poses.
 
 
                                                                             25
                                                                    Prospectus
<PAGE>
 
LOANS OF    For the purpose of achieving income, each Fund may lend its port-
PORTFOLIO   folio securities to brokers, dealers, and other financial institu-
SECURITIES  tions, provided:
                (i) the loan is secured continuously by collateral consisting
                    of U.S. Government securities, cash or cash equivalents
                    (negotiable certificates of deposit, bankers' acceptances
                    or letters of credit) maintained on a daily mark-to-market
                    basis in an amount at least equal to the current market
                    value of the securities loaned;
                (ii) the Fund may at any time call the loan and obtain the re-
                     turn of the securities loaned;
                (iii) the Fund will receive any interest or dividends paid on
                      the loaned securities; and
                (iv) the aggregate market value of securities loaned will not
                     at any time exceed 33 1/3% (25% in the case of the Global
                     Bond Fund II) of the total assets of the Fund.
            Each Fund's performance will continue to reflect changes in the
            value of the securities loaned and will also reflect the receipt
            of either interest, through investment of cash collateral by the
            Fund in permissible investments, or a fee, if the collateral is
            U.S. Government securities. Securities lending involves the risk
            of loss of rights in the collateral or delay in recovery of the
            collateral should the borrower fail to return the security loaned
            or become insolvent. The Funds may pay lending fees to the party
            arranging the loan.
 
 
WHEN-       Each of the Funds may purchase or sell securities on a when-is-
ISSUED,     sued, delayed delivery, or forward commitment basis. These trans-
DELAYED     actions involve a commitment by the Fund to purchase or sell secu-
DELIVERY    rities for a predetermined price or yield, with payment and deliv-
AND FORWARD ery taking place more than seven days in the future, or after a
COMMITMENT  period longer than the customary settlement period for that type
TRANSACTIONSof security. When such purchases are outstanding, the Fund will
            segregate until the settlement date assets determined to be liquid
            by the Adviser in accordance with procedures established by the
            Board of Trustees, in an amount sufficient to meet the purchase
            price. Typically, no income accrues on securities a Fund has com-
            mitted to purchase prior to the time delivery of the securities is
            made, although a Fund may earn income on securities it has segre-
            gated.
               When purchasing a security on a when-issued, delayed delivery,
            or forward commitment basis, the Fund assumes the rights and risks
            of ownership of the security, including the risk of price and
            yield fluctuations, and takes such fluctuations into account when
            determining its net asset value. Because the Fund is not required
            to pay for the security until the delivery date, these risks are
            in addition to the risks associated with the Fund's other invest-
            ments. If the Fund remains substantially fully invested at a time
            when when-issued, delayed delivery, or forward commitment pur-
            chases are outstanding, the purchases may result in a form of lev-
            erage.
               When the Fund has sold a security on a when-issued, delayed de-
            livery, or forward commitment basis, the Fund does not participate
            in future gains or losses with respect to the security. If the
            other party to a transaction fails to deliver or pay for the secu-
            rities, the Fund could miss a favorable price or yield opportunity
            or could suffer a loss. A Fund may dispose of or renegotiate a
            transaction after it is entered into, and may sell when-issued,
            delayed delivery or forward commitment securities before they are
            delivered, which may result in a capital gain or loss. There is no
            percentage limitation on the extent to which the Funds may pur-
            chase or sell securities on a when-issued, delayed delivery, or
            forward commitment basis.
 
 
SHORT SALES Each of the Funds (except the High Yield and StocksPLUS Funds) may
            from time to time effect short sales as part of their overall
            portfolio management strategies, including the use of derivative
            instruments, or to offset potential declines in value of long po-
            sitions in similar securities as those sold short. A short sale
            (other than a short sale against the box) is a transaction in
            which a Fund sells a security it does not own at the time of the
            sale in anticipation that the market price of that security will
            decline. To the extent that a Fund engages in short sales, it must
            (except in the case of short sales "against the box") maintain as-
            set coverage in the form of segregated assets determined to be
            liquid by the Adviser in accordance with procedures established by
            the Board of Trustees or otherwise cover its position in a permis-
            sible manner. A short sale is "against the box" to the extent that
            the Fund contemporaneously owns, or has the right to obtain at no
            added cost, securities identical to those sold short. The Global
            Bond Fund II may only engage in short sales that are "against the
            box."
 
26
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
 
 
FOREIGN     Each of the Funds (except the Municipal Bond Fund and the Long-
SECURITIES  Term U.S. Government Fund) may invest directly in fixed income se-
            curities of non-U.S. issuers. The Money Market and High Yield
            Funds may only invest in U.S. dollar-denominated fixed income se-
            curities of non-U.S. issuers. The StocksPLUS Fund may invest di-
            rectly in foreign equity securities.
               Except for the Emerging Markets Bond Fund, each of the Funds
            will concentrate its investments in securities of issuers based in
            developed countries. However, the Short-Term and Low Duration
            Funds may each invest up to 5% of its assets in securities of is-
            suers based in the emerging market countries in which the Emerging
            Markets Bond Fund may invest, and each of the remaining Fixed In-
            come Funds that may invest in foreign securities may invest up to
            10% of its assets in such securities.
               Individual foreign economies may differ favorably or unfavor-
            ably from the U.S. economy in such respects as growth of gross do-
            mestic product, rate of inflation, capital reinvestment, re-
            sources, self-sufficiency and balance of payments position. The
            securities markets, values of securities, yields, and risks asso-
            ciated with securities markets in different countries may change
            independently of each other. Investing in the securities of is-
            suers in any foreign country involves special risks and considera-
            tions not typically associated with investing in U.S. companies.
            Shareholders should consider carefully the substantial risks in-
            volved in investing in securities issued by companies and govern-
            ments of foreign nations. These risks include: differences in ac-
            counting, auditing and financial reporting standards; generally
            higher commission rates on foreign portfolio transactions; the
            possibility of nationalization, expropriation or confiscatory tax-
            ation; adverse changes in investment or exchange control regula-
            tions (which may include suspension of the ability to transfer
            currency from a country); and political instability which could
            affect U.S. investments in foreign countries. Additionally, for-
            eign securities and dividends and interest payable on those secu-
            rities may be subject to foreign taxes, including taxes withheld
            from payments on those securities. Foreign securities often trade
            with less frequency and volume than domestic securities and there-
            fore may exhibit greater price volatility. Additional costs asso-
            ciated with an investment in foreign securities may include higher
            custodial fees than apply to domestic custodial arrangements and
            transaction costs of foreign currency conversions. Changes in for-
            eign exchange rates also will affect the value of securities de-
            nominated or quoted in currencies other than the U.S. dollar.
               Certain of the Funds, and particularly the Emerging Markets
            Bond Fund, will invest in the securities of issuers based in coun-
            tries with developing economies. Investing in developing (or
            "emerging market") countries involves certain risks not typically
            associated with investing in U.S. securities, and imposes risks
            greater than, or in addition to, risks of investing in foreign,
            developed countries. A number of emerging market countries re-
            strict, to varying degrees, foreign investment in securities. Re-
            patriation of investment income, capital, and the proceeds of
            sales by foreign investors may require governmental registration
            and/or approval in some emerging market countries. A number of the
            currencies of emerging market countries have experienced signifi-
            cant declines against the U.S. dollar in recent years, and devalu-
            ation may occur subsequent to investments in these currencies by a
            Fund. Inflation and rapid fluctuations in inflation rates have
            had, and may continue to have, negative effects on the economies
            and securities markets of certain emerging market countries. Many
            of the emerging securities markets are relatively small, have low
            trading volumes, suffer periods of relative illiquidity, and are
            characterized by significant price volatility. There is a risk in
            emerging market countries that a future economic or political cri-
            sis could lead to price controls, forced mergers of companies, ex-
            propriation or confiscatory taxation, seizure, nationalization, or
            creation of government monopolies, any of which may have a detri-
            mental effect on a Fund's investment.
               Additional risks of investing in emerging market countries may
            include: currency exchange rate fluctuations; greater social, eco-
            nomic and political uncertainty and instability (including the
            risk of war); more substantial governmental involvement in the
            economy; less governmental supervision and regulation of the secu-
            rities markets and participants in those markets; unavailability
            of currency hedging techniques in certain emerging market coun-
            tries; the fact that companies in emerging market countries may be
            newly organized and may be smaller and less seasoned companies;
            the difference in, or lack of, auditing and financial reporting
            standards, which may result in unavailability of material informa-
            tion about issuers; the risk that it may be more difficult to ob-
            tain and/or enforce a judgment in a court outside
                                                                    Prospectus
                                                                              27
<PAGE>
 
            the United States; and significantly smaller market capitalization
            of securities markets. Also, any change in the leadership or poli-
            cies of Eastern European countries, or the countries that exercise
            a significant influence over those countries, may halt the expan-
            sion of or reverse the liberalization of foreign investment poli-
            cies now occurring and adversely affect existing investment oppor-
            tunities.
               In addition, emerging securities markets may have different
            clearance and settlement procedures, which may be unable to keep
            pace with the volume of securities transactions or otherwise make
            it difficult to engage in such transactions. Settlement problems
            may cause a Fund to miss attractive investment opportunities, hold
            a portion of its assets in cash pending investment, or delay in
            disposing of a portfolio security. Such a delay could result in
            possible liability to a purchaser of the security.
               Each of the Fixed Income Funds (except the Municipal Bond and
            Long-Term U.S. Government Funds) may invest in Brady Bonds. Brady
            Bonds are securities created through the exchange of existing com-
            mercial bank loans to sovereign entities for new obligations in
            connection with debt restructurings under a debt restructuring
            plan introduced by former U.S. Secretary of the Treasury, Nicholas
            F. Brady. Brady Bonds have been issued only recently, and for that
            reason do not have a long payment history. Brady Bonds may be col-
            lateralized or uncollateralized, are issued in various currencies
            (but primarily the U.S. dollar), and are actively traded in the
            over-the-counter secondary market. Brady Bonds are not considered
            to be U.S. Government securities. In light of the residual risk of
            Brady Bonds and, among other factors, the history of defaults with
            respect to commercial bank loans by public and private entities in
            countries issuing Brady Bonds, investments in Brady Bonds may be
            viewed as speculative. There can be no assurance that Brady Bonds
            acquired by a Fund will not be subject to restructuring arrange-
            ments or to requests for new credit, which may cause the Fund to
            suffer a loss of interest or principal on any of its holdings. For
            further information, see the Statement of Additional Information.
               Certain of the Funds also may invest in sovereign debt (other
            than Brady Bonds) issued by governments, their agencies or instru-
            mentalities, or other government-related entities located in
            emerging market countries. Holders of sovereign debt may be re-
            quested to participate in the rescheduling of such debt and to ex-
            tend further loans to governmental entities. In addition, there is
            no bankruptcy proceeding by which defaulted sovereign debt may be
            collected.
               A Fund's investments in foreign currency denominated debt obli-
            gations and hedging activities will likely produce a difference
            between its book income and its taxable income. This difference
            may cause a portion of the Fund's income distributions to consti-
            tute returns of capital for tax purposes or require the Fund to
            make distributions exceeding book income to qualify as a regulated
            investment company for federal tax purposes.
 
 
FOREIGN     Foreign currency exchange rates may fluctuate significantly over
CURRENCY    short periods of time. They generally are determined by the forces
TRANSACTIONSof supply and demand in the foreign exchange markets and the rela-
            tive merits of investments in different countries, actual or per-
            ceived changes in interest rates and other complex factors, as
            seen from an international perspective. Currency exchange rates
            also can be affected unpredictably by intervention (or the failure
            to intervene) by U.S. or foreign governments or central banks, by
            currency controls or political developments in the U.S. or abroad.
            For example, significant uncertainty surrounds the proposed intro-
            duction of the euro (a common currency for the European Union) in
            January 1999 and its effect on the value of securities denominated
            in local European currencies. These and other currencies in which
            the Funds' assets are denominated may be devalued against the U.S.
            dollar, resulting in a loss to the Funds.
               All Funds that may invest in securities denominated in foreign
            currencies may buy and sell foreign currencies on a spot and for-
            ward basis to reduce the risks of adverse changes in foreign ex-
            change rates. A forward foreign currency exchange contract in-
            volves an obligation to purchase or sell a specific currency at a
            future date, which may be any fixed number of days from the date
            of the contract agreed upon by the parties, at a price set at the
            time of the contract. By entering into a forward foreign currency
            exchange contract, the Fund "locks in" the exchange rate between
            the currency it will deliver and the currency it will receive for
            the duration of the contract. As a result, a Fund reduces its ex-
            posure to changes in the value of the currency it will deliver and
            increases its exposure to changes in the value of the
 
28
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            currency it will exchange into. The effect on the value of a Fund
            is similar to selling securities denominated in one currency and
            purchasing securities denominated in another. Contracts to sell
            foreign currency would limit any potential gain which might be re-
            alized by a Fund if the value of the hedged currency increases. A
            Fund may enter into these contracts for the purpose of hedging
            against foreign exchange risk arising from the Fund's investment
            or anticipated investment in securities denominated in foreign
            currencies. A Fund also may enter into these contracts for pur-
            poses of increasing exposure to a foreign currency or to shift ex-
            posure to foreign currency fluctuations from one country to anoth-
            er. A Fund may use one currency (or a basket of currencies) to
            hedge against adverse changes in the value of another currency (or
            a basket of currencies) when exchange rates between the two cur-
            rencies are positively correlated. Each Fund will segregate assets
            determined to be liquid by the Adviser in accordance with proce-
            dures established by the Board of Trustees, to cover its obliga-
            tions under forward foreign currency exchange contracts entered
            into for non-hedging purposes.
               All Funds that may invest in securities denominated in foreign
            currencies may invest in options on foreign currencies and foreign
            currency futures and options thereon. The Funds also may invest in
            foreign currency exchange-related securities, such as foreign cur-
            rency warrants and other instruments whose return is linked to
            foreign currency exchange rates. Each Fund that may invest in se-
            curities denominated in foreign currencies, except the Emerging
            Markets Bond Fund, will use these techniques to hedge at least 75%
            of its exposure to foreign currency. For a description of these
            instruments, see "Derivative Instruments" below and the Statement
            of Additional Information.
 
 
HIGH YIELD  The High Yield Fund invests at least 65% of its assets, and the
SECURITIES  Emerging Markets Bond Fund may invest up to 100% of its assets, in
("JUNK      fixed income securities rated lower than Baa by Moody's or lower
BONDS")     than BBB by S&P but rated at least B by Moody's or S&P (or, if not
            rated, determined by the Adviser to be of comparable quality). In
            addition, each of the Short-Term, Low Duration, Real Return Bond,
            Total Return, Global Bond II, Foreign Bond, Strategic Balanced and
            StocksPLUS Funds may invest up to 10% of its assets in such secu-
            rities. The Municipal Bond Fund may invest up to 10% of its assets
            in securities rated lower than Baa by Moody's or BBB by S&P but
            rated at least Ba by Moody's or BB by S&P. Securities rated lower
            than Baa by Moody's or lower than BBB by S&P are sometimes re-
            ferred to as "high yield" or "junk" bonds. Securities rated Baa
            are considered by Moody's to have some speculative characteris-
            tics. Investors should consider the following risks associated
            with high yield securities before investing in these Funds.
               Investing in high yield securities involves special risks in
            addition to the risks associated with investments in higher rated
            fixed income securities. High yield securities may be regarded as
            predominately speculative with respect to the issuer's continuing
            ability to meet principal and interest payments. Analysis of the
            creditworthiness of issuers of high yield securities may be more
            complex than for issuers of higher quality debt securities, and
            the ability of a Fund to achieve its investment objective may, to
            the extent of its investments in high yield securities, be more
            dependent upon such creditworthiness analysis than would be the
            case if the Fund were investing in higher quality securities.
               High yield securities may be more susceptible to real or per-
            ceived adverse economic and competitive industry conditions than
            higher grade securities. The prices of high yield securities have
            been found to be less sensitive to interest rate changes than more
            highly rated investments, but more sensitive to adverse economic
            downturns or individual corporate developments. A projection of an
            economic downturn or of a period of rising interest rates, for ex-
            ample, could cause a decline in high yield security prices because
            the advent of a recession could lessen the ability of a highly
            leveraged company to make principal and interest payments on its
            debt securities. If the issuer of high yield securities defaults,
            a Fund may incur additional expenses to seek recovery. In the case
            of high yield securities structured as zero coupon or payment-in-
            kind securities, the market prices of such securities are affected
            to a greater extent by interest rate changes, and therefore tend
            to be more volatile than securities which pay interest periodi-
            cally and in cash.
               The secondary markets on which high yield securities are traded
            may be less liquid than the market for higher grade securities.
            Less liquidity in the secondary trading markets could adversely
            affect and cause large fluctuations in the daily net asset value
            of a Fund's shares. Adverse publicity and investor perceptions,
            whether or not based on fundamental analysis, may decrease the
            values and liquidity of high yield securities, especially in a
            thinly traded market.
                                                                    Prospectus
                                                                              29
<PAGE>
 
               The use of credit ratings as the sole method of evaluating high
            yield securities can involve certain risks. For example, credit
            ratings evaluate the safety of principal and interest payments,
            not the market value risk of high yield securities. Also, credit
            rating agencies may fail to change credit ratings in a timely
            fashion to reflect events since the security was last rated. The
            Adviser does not rely solely on credit ratings when selecting se-
            curities for the Funds, and develops its own independent analysis
            of issuer credit quality. If a credit rating agency changes the
            rating of a portfolio security held by a Fund, the Fund may retain
            the portfolio security if the Adviser deems it in the best inter-
            est of shareholders.
               During the year ended March 31, 1998, based upon the dollar-
            weighted average ratings of the Funds' portfolio holdings at the
            end of each month in the Funds' fiscal year, each operational Fund
            that may invest greater than 5% of its assets in securities rated
            below investment grade had the following percentages of its net
            assets invested in securities rated in the categories indicated as
            rated by Moody's (or, if unrated, determined by the Adviser to be
            of comparable quality). See "Appendix B--Description of Securities
            Ratings," for further information.
 
 
              FIXED INCOME SECURITIES RATINGS
 
<TABLE>
<CAPTION>
                                                          BELOW
           FUND                   PRIME 1 AAA  AA    A   PRIME 1 BAA  BA    B
              -----------------------------------------------------------------
           <S>                    <C>     <C>  <C>  <C>  <C>     <C>  <C>  <C>
           SHORT-TERM                17%   35%   2%  15%    16%    9%   6%   0%
              -----------------------------------------------------------------
           LOW DURATION               6    75    1    1      5     7    5    0
              -----------------------------------------------------------------
           TOTAL RETURN              20    47    0   13      6     8    6    0
              -----------------------------------------------------------------
           HIGH YIELD                 5     2    0    0      2     6   43   42
              -----------------------------------------------------------------
           GLOBAL BOND II            65    21    3    6      0     2    3    0
              -----------------------------------------------------------------
           FOREIGN BOND              54    31    4    2      1     2    6    0
              -----------------------------------------------------------------
           EMERGING MARKETS BOND     16    14    0    0      0    18   47    5
              -----------------------------------------------------------------
           STRATEGIC BALANCED        17    58    1    9      4     2    9    0
              -----------------------------------------------------------------
           STOCKSPLUS                26    38    1   10     11     7    7    0
</TABLE>
 
 
               These figures are intended solely to provide disclosure about
            each Fund's asset composition during its most recent fiscal year.
            The asset composition after this time may or may not be approxi-
            mately the same as represented by such figures. In addition, the
            categories reflect ratings by Moody's, and ratings assigned by S&P
            may not be consistent with ratings assigned by Moody's or other
            credit ratings services, and the Adviser may not necessarily agree
            with a rating assigned by any credit rating agency.
 
 
DERIVATIVE  To the extent permitted by the investment objectives and policies
INSTRUMENTS of the Funds, the Funds may (except the Money Market Fund) pur-
            chase and write call and put options on securities, securities in-
            dexes and foreign currencies, and enter into futures contracts and
            use options on futures contracts as further described below. The
            Funds (except the Money Market Fund and the Municipal Bond Fund)
            also may enter into swap agreements with respect to foreign cur-
            rencies, interest rates, and securities indexes. The Funds may use
            these techniques to hedge against changes in interest rates, for-
            eign currency exchange rates or securities prices or as part of
            their overall investment strategies. The Funds (except the Money
            Market Fund and the Municipal Bond Fund) may also purchase and
            sell options relating to foreign currencies for purposes of in-
            creasing exposure to a foreign currency or to shift exposure to
            foreign currency fluctuations from one country to another. Each
            Fund will segregate assets determined to be liquid by the Adviser
            in accordance with procedures established by the Board of Trustees
            (or, as permitted by applicable regulation, enter into certain
            offsetting positions) to cover its obligations under options,
            futures, and swaps to limit leveraging of the Fund.
               Derivative instruments are considered for these purposes to
            consist of securities or other instruments whose value is derived
            from or related to the value of some other instrument or asset,
            and not to include those securities whose payment of principal
            and/or interest depends upon cash flows from underlying assets,
            such as mortgage-related or asset-backed securities. Each Fund
            (except the Money Market Fund and the Municipal Bond Fund) may in-
            vest all of its
 
30
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            assets in derivative instruments, subject only to the Fund's in-
            vestment objective and policies. The value of some derivative in-
            struments in which the Funds invest may be particularly sensitive
            to changes in prevailing interest rates, and, like the other in-
            vestments of the Funds, the ability of a Fund to successfully uti-
            lize these instruments may depend in part upon the ability of the
            Adviser to forecast interest rates and other economic factors cor-
            rectly. If the Adviser incorrectly forecasts such factors and has
            taken positions in derivative instruments contrary to prevailing
            market trends, the Funds could be exposed to the risk of loss.
               The Funds might not employ any of the strategies described be-
            low, and no assurance can be given that any strategy used will
            succeed. If the Adviser incorrectly forecasts interest rates, mar-
            ket values or other economic factors in utilizing a derivatives
            strategy for a Fund, the Fund might have been in a better position
            if it had not entered into the transaction at all. Also, suitable
            derivative transactions may not be available in all circumstances.
            The use of these strategies involves certain special risks, in-
            cluding a possible imperfect correlation, or even no correlation,
            between price movements of derivative instruments and price move-
            ments of related investments. While some strategies involving de-
            rivative instruments can reduce the risk of loss, they can also
            reduce the opportunity for gain or even result in losses by off-
            setting favorable price movements in related investments or other-
            wise, due to the possible inability of a Fund to purchase or sell
            a portfolio security at a time that otherwise would be favorable
            or the possible need to sell a portfolio security at a disadvanta-
            geous time because the Fund is required to maintain asset coverage
            or offsetting positions in connection with transactions in deriva-
            tive instruments, and the possible inability of a Fund to close
            out or to liquidate its derivatives positions. In addition, a
            Fund's use of such instruments may cause the Fund to realize
            higher amounts of short-term capital gains (generally taxed at or-
            dinary income tax rates) than if it had not used such instruments.
 
            OPTIONS ON SECURITIES, SECURITIES INDEXES, AND CURRENCIES A Fund
            may purchase put options on securities and indexes. One purpose of
            purchasing put options is to protect holdings in an underlying or
            related security against a substantial decline in market value. A
            Fund may also purchase call options on securities and indexes. One
            purpose of purchasing call options is to protect against substan-
            tial increases in prices of securities the Fund intends to pur-
            chase pending its ability to invest in such securities in an or-
            derly manner. An option on a security (or index) is a contract
            that gives the holder of the option, in return for a premium, the
            right to buy from (in the case of a call) or sell to (in the case
            of a put) the writer of the option the security underlying the op-
            tion (or the cash value of the index) at a specified exercise
            price at any time during the term of the option. The writer of an
            option on a security has the obligation upon exercise of the op-
            tion to deliver the underlying security upon payment of the exer-
            cise price or to pay the exercise price upon delivery of the un-
            derlying security. Upon exercise, the writer of an option on an
            index is obligated to pay the difference between the cash value of
            the index and the exercise price multiplied by the specified mul-
            tiplier for the index option. An index is designed to reflect
            specified facets of a particular financial or securities market, a
            specific group of financial instruments or securities, or certain
            economic indicators.
               A Fund may sell put or call options it has previously pur-
            chased, which could result in a net gain or loss depending on
            whether the amount realized on the sale is more or less than the
            premium and other transaction costs paid on the put or call option
            which is sold. A Fund may write a call or put option only if the
            option is "covered" by the Fund holding a position in the under-
            lying securities or by other means which would permit immediate
            satisfaction of the Fund's obligation as writer of the option.
            Prior to exercise or expiration, an option may be closed out by an
            offsetting purchase or sale of an option of the same series.
               The Funds may write covered straddles consisting of a combina-
            tion of a call and a put written on the same underlying security.
            A straddle will be covered when sufficient assets are deposited to
            meet the Funds' immediate obligations. The Funds may use the same
            liquid assets to cover both the call and put options where the ex-
            ercise price of the call and put are the same, or the exercise
            price of the call is higher than that of the put. In such cases,
            the Funds will also segregate liquid assets equivalent to the
            amount, if any, by which the put is "in the money."
               The purchase and writing of options involves certain risks.
            During the option period, the covered call writer has, in return
            for the premium on the option, given up the opportunity to profit
            from a price increase in the underlying security
 
                                                                             31
                                                                   Prospectus
<PAGE>
 
            above the exercise price, but, as long as its obligation as a
            writer continues, has retained the risk of loss should the price
            of the underlying security decline. The writer of an option has no
            control over the time when it may be required to fulfill its obli-
            gation as a writer of the option. Once an option writer has re-
            ceived an exercise notice, it cannot effect a closing purchase
            transaction in order to terminate its obligation under the option
            and must deliver the underlying security at the exercise price. If
            a put or call option purchased by the Fund is not sold when it has
            remaining value, and if the market price of the underlying secu-
            rity remains equal to or greater than the exercise price (in the
            case of a put), or remains less than or equal to the exercise
            price (in the case of a call), the Fund will lose its entire in-
            vestment in the option. Also, where a put or call option on a par-
            ticular security is purchased to hedge against price movements in
            a related security, the price of the put or call option may move
            more or less than the price of the related security. There can be
            no assurance that a liquid market will exist when a Fund seeks to
            close out an option position. Furthermore, if trading restrictions
            or suspensions are imposed on the options markets, a Fund may be
            unable to close out a position.
               Funds that invest in foreign currency-denominated securities
            may buy or sell put and call options on foreign currencies. Cur-
            rency options traded on U.S. or other exchanges may be subject to
            position limits which may limit the ability of a Fund to reduce
            foreign currency risk using such options.
               Over-the-counter options in which certain Funds may invest dif-
            fer from traded options in that they are two-party contracts, with
            price and other terms negotiated between buyer and seller, and
            generally do not have as much market liquidity as exchange-traded
            options. The Funds may be required to treat as illiquid over-the-
            counter options purchased and securities being used to cover cer-
            tain written over-the-counter options.
 
            SWAP AGREEMENTS The Funds (except the Money Market Fund and the
            Municipal Bond Fund) may enter into interest rate, index, equity
            and currency exchange rate swap agreements. These transactions
            would be entered into in an attempt to obtain a particular return
            when it is considered desirable to do so, possibly at a lower cost
            to the Fund than if the Fund had invested directly in the asset
            that yielded the desired return. Swap agreements are two-party
            contracts entered into primarily by institutional investors for
            periods ranging from a few weeks to more than one year. In a stan-
            dard swap transaction, two parties agree to exchange the returns
            (or differentials in rates of return) earned or realized on par-
            ticular predetermined investments or instruments, which may be ad-
            justed for an interest factor. The gross returns to be exchanged
            or "swapped" between the parties are generally calculated with re-
            spect to a "notional amount," i.e., the return on or increase in
            value of a particular dollar amount invested at a particular in-
            terest rate, in a particular foreign currency, or in a "basket" of
            securities representing a particular index. Forms of swap agree-
            ments include interest rate caps, under which, in return for a
            premium, one party agrees to make payments to the other to the ex-
            tent that interest rates exceed a specified rate, or "cap"; inter-
            est rate floors, under which, in return for a premium, one party
            agrees to make payments to the other to the extent that interest
            rates fall below a specified level, or "floor"; and interest rate
            collars, under which a party sells a cap and purchases a floor or
            vice versa in an attempt to protect itself against interest rate
            movements exceeding given minimum or maximum levels.
               Most swap agreements entered into by the Funds calculate the
            obligations of the parties to the agreement on a "net basis." Con-
            sequently, a Fund's current obligations (or rights) under a swap
            agreement will generally be equal only to the net amount to be
            paid or received under the agreement based on the relative values
            of the positions held by each party to the agreement (the "net
            amount"). A Fund's current obligations under a swap agreement will
            be accrued daily (offset against amounts owed to the Fund), and
            any accrued but unpaid net amounts owed to a swap counterparty
            will be covered by the segregation of assets determined to be liq-
            uid by the Adviser in accordance with procedures established by
            the Board of Trustees, to limit any potential leveraging of the
            Fund's portfolio. Obligations under swap agreements so covered
            will not be construed to be "senior securities" for purposes of
            the Funds' investment restriction concerning senior securities. A
            Fund will not enter into a swap agreement with any single party if
            the net amount owed or to be received under existing contracts
            with that party would exceed 5% of the Fund's assets.
               Whether a Fund's use of swap agreements will be successful in
            furthering its investment objective will depend on the Adviser's
            ability to predict correctly whether certain types of investments
            are likely to produce greater returns than
 
32
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            other investments. Because they are two-party contracts and be-
            cause they may have terms of greater than seven days, swap agree-
            ments may be considered to be illiquid investments. Moreover, a
            Fund bears the risk of loss of the amount expected to be received
            under a swap agreement in the event of the default or bankruptcy
            of a swap agreement counterparty. The Funds will enter into swap
            agreements only with counterparties that meet certain standards
            for creditworthiness (generally, such counterparties would have to
            be eligible counterparties under the terms of the Funds' repur-
            chase agreement guidelines). Certain restrictions imposed on the
            Funds by the Internal Revenue Code may limit the Funds' ability to
            use swap agreements. The swaps market is a relatively new market
            and is largely unregulated. It is possible that developments in
            the swaps market, including potential government regulation, could
            adversely affect a Fund's ability to terminate existing swap
            agreements or to realize amounts to be received under such agree-
            ments.
 
            FUTURES CONTRACTS AND OPTIONS ON FUTURES CONTRACTS Each of the
            Fixed Income Funds (except the Money Market and Municipal Bond
            Funds) may invest in interest rate futures contracts and options
            thereon ("futures options"), and to the extent it may invest in
            foreign currency-denominated securities, may also invest in for-
            eign currency futures contracts and options thereon. The Municipal
            Bond Fund may purchase and sell futures contracts on U.S. Govern-
            ment securities and Municipal Bonds, as well as purchase put and
            call options on such futures contracts. The Strategic Balanced and
            StocksPLUS Funds may invest in interest rate, stock index and for-
            eign currency futures contracts and options thereon.
               There are several risks associated with the use of futures and
            futures options for hedging purposes. There can be no guarantee
            that there will be a correlation between price movements in the
            hedging vehicle and in the portfolio securities being hedged. An
            incorrect correlation could result in a loss on both the hedged
            securities in a Fund and the hedging vehicle, so that the portfo-
            lio return might have been greater had hedging not been attempted.
            There can be no assurance that a liquid market will exist at a
            time when a Fund seeks to close out a futures contract or a
            futures option position. Most futures exchanges and boards of
            trade limit the amount of fluctuation permitted in futures con-
            tract prices during a single day; once the daily limit has been
            reached on a particular contract, no trades may be made that day
            at a price beyond that limit. In addition, certain of these in-
            struments are relatively new and without a significant trading
            history. As a result, there is no assurance that an active second-
            ary market will develop or continue to exist. Lack of a liquid
            market for any reason may prevent a Fund from liquidating an unfa-
            vorable position, and the Fund would remain obligated to meet mar-
            gin requirements until the position is closed.
               The Funds may write covered straddles consisting of a call and
            a put written on the same underlying futures contract. A straddle
            will be covered when sufficient assets are deposited to meet the
            Funds' immediate obligations. A Fund may use the same liquid as-
            sets to cover both the call and put options where the exercise
            price of the call and put are the same, or the exercise price of
            the call is higher than that of the put. In such cases, the Funds
            will also segregate liquid assets equivalent to the amount, if
            any, by which the put is "in the money."
               The Funds will only enter into futures contracts or futures op-
            tions which are standardized and traded on a U.S. or foreign ex-
            change or board of trade, or similar entity, or quoted on an auto-
            mated quotation system. Each Fund will use financial futures con-
            tracts and related options only for "bona fide hedging" purposes,
            as such term is defined in applicable regulations of the CFTC or,
            with respect to positions in financial futures and related options
            that do not qualify as "bona fide hedging" positions, will enter
            such positions only to the extent that aggregate initial margin
            deposits plus premiums paid by it for open futures option posi-
            tions, less the amount by which any such positions are "in-the-
            money," would not exceed 5% of the Fund's net assets.
 
 
HYBRID
INSTRUMENTS A hybrid instrument can combine the characteristics of securities,
            futures, and options. For example, the principal amount or
            interest rate of a hybrid could be tied (positively or negatively)
            to the price of some commodity, currency or securities index or
            another interest rate (each a "benchmark"). The interest rate or
            (unlike most fixed income securities) the principal amount payable
            at maturity of a hybrid security may be increased or decreased,
            depending on changes in the value of the benchmark.
 
                                                                             33
                                                                    Prospectus
<PAGE>
 
               Hybrids can be used as an efficient means of pursuing a variety
            of investment goals, including currency hedging, duration manage-
            ment, and increased total return. Hybrids may not bear interest or
            pay dividends. The value of a hybrid or its interest rate may be a
            multiple of a benchmark and, as a result, may be leveraged and
            move (up or down) more steeply and rapidly than the benchmark.
            These benchmarks may be sensitive to economic and political
            events, such as commodity shortages and currency devaluations,
            which cannot be readily foreseen by the purchaser of a hybrid. Un-
            der certain conditions, the redemption value of a hybrid could be
            zero. Thus, an investment in a hybrid may entail significant mar-
            ket risks that are not associated with a similar investment in a
            traditional, U.S. dollar-denominated bond that has a fixed princi-
            pal amount and pays a fixed rate or floating rate of interest. The
            purchase of hybrids also exposes a Fund to the credit risk of the
            issuer of the hybrids. These risks may cause significant fluctua-
            tions in the net asset value of the Fund. Accordingly, no Fund
            will invest more than 5% of its assets in hybrid instruments.
               Certain issuers of structured products such as hybrid instru-
            ments may be deemed to be investment companies as defined in the
            1940 Act. As a result, the Funds' investments in these products
            will be subject to limits applicable to investments in investment
            companies and may be subject to restrictions contained in the 1940
            Act.
 
 
CATASTROPHE Each of the Fixed Income Funds (except the Money Market Fund) and
BONDS       the StocksPLUS Fund may invest in "catastrophe bonds." Catastrophe
            bonds are fixed income securities, for which the return of princi-
            pal and payment of interest is contingent on the non-occurrence of
            a specific "trigger" catastrophic event, such as a hurricane or an
            earthquake. They may be issued by government agencies, insurance
            companies, reinsurers, special purpose corporations or other on-
            shore or off-shore entities. If a trigger event causes losses ex-
            ceeding a specific amount in the geographic region and time period
            specified in a bond, a Fund investing in the bond may lose a por-
            tion or all of its principal invested in the bond. If no trigger
            event occurs, the Fund will recover its principal plus interest.
            For some catastrophe bonds, the trigger event or losses may be
            based on companywide losses, index-portfolio losses, industry in-
            dices, or readings of scientific instruments rather than specified
            actual losses. Often the catastrophe bonds provide for extensions
            of maturity that are mandatory, or optional at the discretion of
            the issuer, in order to process and audit loss claims in those
            cases where a trigger event has, or possibly has, occurred. In ad-
            dition to the specified trigger events, catastrophe bonds may also
            expose the Fund to certain unanticipated risks including but not
            limited to issuer (credit) default, adverse regulatory or juris-
            dictional interpretations, and adverse tax consequences.
               Catastrophe bonds are a relatively new type of financial in-
            strument. As such, there is no significant trading history of
            these securities, and there can be no assurance that a liquid mar-
            ket in these instruments will develop. See "Illiquid Securities"
            below. Lack of a liquid market may impose the risk of higher
            transaction costs and the possibility that a Fund may be forced to
            liquidate positions when it would not be advantageous to do so.
            Catastrophe bonds are typically rated, and a Fund will only invest
            in catastrophe bonds that meet the credit quality requirements for
            the Fund.
 
 
 
INVESTMENT  Each of the Funds may invest up to 10% of its assets in securities
IN          of other investment companies, such as closed-end management in-
INVESTMENT  vestment companies, or in pooled accounts or other investment ve-
COMPANIES   hicles. As a shareholder of an investment company, a Fund may in-
            directly bear service and other fees which are in addition to the
            fees the Fund pays its service providers.
 
 
PORTFOLIO
TURNOVER    The length of time a Fund has held a particular security is not
            generally a consideration in investment decisions. The investment
            policies of a Fund may lead to frequent changes in the Fund's in-
            vestments, particularly in periods of volatile market movements. A
            change in the securities held by a Fund is known as "portfolio
            turnover." High portfolio turnover (e.g., over 100%) involves cor-
            respondingly greater expenses to a Fund, including commissions or
            dealer mark-ups and other transaction costs on the sale of securi-
            ties and reinvestments in other securities. See "Management of the
            Trust--Portfolio Transactions." Such sales may result in realiza-
            tion of taxable capital gains (including short-term capital gains
            which are generally taxed at ordinary income tax rates). See "Tax-
            es." The portfolio turnover rate for certain of the
 
34
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Funds is set forth under "Financial Highlights." The portfolio
            turnover rate for certain of the Funds, which offer Institutional
            or Administrative Class shares, is incorporated by reference in
            the Statement of Additional Information.
 
 
ILLIQUID    Each of the Funds may invest up to 15% of its net assets in illiq-
SECURITIES  uid securities (10% in the case of the Money Market Fund). Certain
            illiquid securities may require pricing at fair value as deter-
            mined in good faith under the supervision of the Board of Trust-
            ees. The Adviser may be subject to significant delays in disposing
            of illiquid securities, and transac- tions in illiquid securities
            may entail registration expenses and other transaction costs that
            are higher than those for transactions in liquid securities. The
            term "illiquid securities" for this purpose means securities that
            cannot be disposed of within seven days in the ordinary course of
            business at approximately the amount at which a Fund has valued
            the securities. Illiquid securities are considered to include,
            among other things, written over-the-counter options, securities
            or other liquid assets being used as cover for such options, re-
            purchase agreements with maturities in excess of seven days, cer-
            tain loan participation interests, fixed time deposits which are
            not subject to prepayment or provide for withdrawal penalties upon
            prepayment (other than overnight deposits), securities that are
            subject to legal or contractual restrictions on resale and other
            securities which legally or in the Adviser's opinion may be deemed
            illiquid (not including securities issued pursuant to Rule 144A
            under the Securities Act of 1933 and certain commercial paper that
            Pacific Investment Management has determined to be liquid under
            procedures approved by the Board of Trustees).
               Illiquid securities may include privately placed securities,
            which are sold directly to a small number of investors, usually
            institutions. Unlike public offerings, such securities are not
            registered under the federal securities laws. Although certain of
            these securities may be readily sold, for example, under Rule
            144A, others may be illiquid, and their sale may involve substan-
            tial delays and additional costs.
 
 
SERVICE     Many of the services provided to the Funds depend on the smooth
SYSTEMS--   functioning of computer systems. Many systems in use today cannot
YEAR 2000   distinguish between the year 1900 and the year 2000. Should any of
PROBLEM     the service systems fail to process information properly, that
            could have an adverse impact on the Funds' operations and services
            provided to shareholders. The Adviser, Distributor, Shareholder
            Servicing and Transfer Agent, Custodian, and certain other service
            providers to the Funds have reported that each is working toward
            mitigating the risks associated with the so-called "year 2000
            problem." However, there can be no assurance that the problem will
            be corrected in all respects and that the Funds' operations and
            services provided to shareholders will not be adversely affected,
            nor can there be any assurance that the year 2000 problem will not
            have an adverse effect on the entities whose securities are held
            by the Funds or on domestic or global markets or economies,
            generally.
 
            Performance Information
 
            From time to time the Trust may make available certain information
            about the performance of the Class A, Class B and Class C shares
            of some or all of the Funds. Information about a Fund's perfor-
            mance is based on that Fund's (or its predecessor's) record to a
            recent date and is not intended to indicate future performance.
            Performance information is computed separately for each Fund's
            Class A, Class B and Class C shares in accordance with the formu-
            las described below. Because Class B and Class C shares bear the
            expense of the distribution fee attending the deferred sales
            charge (Class B) and asset based sales charge (Class C) alterna-
            tives and certain other expenses, it is expected that, under nor-
            mal circumstances, the yield and the level of performance of a
            Fund's Class B and Class C shares will be lower than that of the
            Fund's Class A shares although an investment in Class B or Class C
            shares is not reduced by the front-end sales charge generally ap-
            plicable to an investment in Class A shares.
               From time to time, the yield and total return for each class of
            shares of the Funds may be included in advertisements or reports
            to shareholders or prospective investors. Yield quotations for the
            Money Market Fund may include current yield and effective yield.
            Current yield will be based on income received by a hypothetical
            investment over a
 
                                                                             35
                                                                    Prospectus
<PAGE>
 
            given seven-day period (less expenses accrued during the period)
            and "annualized" (i.e., assuming that the seven-day yield would be
            received for 52 weeks, stated in terms of an annual percentage re-
            turn on the investment). Effective yield for the Fund is calcu-
            lated in the manner similar to that used to calculate current
            yield, but reflects the compounding effect on earnings of rein-
            vested dividends. For the remaining Funds, quotations of yield for
            a Fund or class will be based on the investment income per share
            (as defined by the Securities and Exchange Commission) during a
            particular 30-day (or one-month) period (including dividends and
            interest), less expenses accrued during the period ("net invest-
            ment income"), and will be computed by dividing net investment in-
            come by the maximum public offering price per share on the last
            day of the period. The tax equivalent yield of the Municipal Bond
            Fund's Class A, Class B and Class C shares may also be advertised,
            calculated like yield except that, for any given tax bracket, net
            investment income will be calculated as the sum of (i) any taxable
            income of the class plus (ii) the tax exempt income of the class
            divided by the difference between 1 and the effective federal in-
            come tax rates for taxpayers in that tax bracket.
               The total return of Class A, Class B and/or Class C shares of
            all Funds may be included in advertisements or other written mate-
            rial. When a Fund's total return is advertised with respect to its
            Class A, Class B and Class C shares, it will be calculated for the
            past year, the past five years, and the past ten years (or if the
            Fund has been offered for a period shorter than one, five or ten
            years, that period will be substituted) since the establishment of
            the Fund (or its predecessor series of PIMCO Advisors Funds for
            the Global Bond Fund II), as more fully described in the Statement
            of Additional Information. For periods prior to the initial offer-
            ing date of a particular class of shares, total return presenta-
            tions for the class will be based on the historical performance of
            an older class of the Fund (if any) restated to reflect current
            sales charges (if any) of the newer class. The older class to be
            used in each case is set forth in the Statement of Additional In-
            formation. For these purposes, the performance of the older class
            will also be restated to reflect any different operating expenses
            (such as different administrative fees and/or 12b-1/servicing fee
            charges) associated with the newer class. In certain cases, such a
            restatement will result in performance of the newer class which is
            higher than if the performance of the older class were not re-
            stated to reflect the different operating expenses of the newer
            class. In such cases, the Trust's advertisements will also, to the
            extent appropriate, show the lower performance figure reflecting
            the actual operating expenses incurred by the older class for pe-
            riods prior to the initial offering date of the newer class. Total
            return for each class is measured by comparing the value of an in-
            vestment in the Fund at the beginning of the relevant period (in
            the case of Class A shares, giving effect to the maximum initial
            sales charge) to the redemption value of the investment in the
            Fund at the end of the period (assuming immediate reinvestment of
            any dividends or capital gains distributions at net asset value
            and giving effect to the deduction of the maximum CDSC which would
            be payable). Total return may be advertised using alternative
            methods that reflect all elements of return, but that may be ad-
            justed to reflect the cumulative impact of alternative fee and ex-
            pense structures, such as the currently effective advisory and ad-
            ministrative fees for the Funds.
               The Funds may also provide current distribution information to
            its shareholders in shareholder reports or other shareholder com-
            munications, or in certain types of sales literature provided to
            prospective investors. Current distribution information for a par-
            ticular class of a Fund will be based on distributions for a spec-
            ified period (i.e., total dividends from net investment income),
            divided by the relevant class net asset value per share on the
            last day of the period and annualized. The rate of current distri-
            butions does not reflect deductions for unrealized losses from
            transactions in derivative instruments such as options and
            futures, which may reduce total return. Current distribution rates
            differ from standardized yield rates in that they represent what a
            class of a Fund has declared and paid to shareholders as of the
            end of a specified period rather than the Fund's actual net in-
            vestment income for that period.
               Performance information for the Trust may also be compared to
            various unmanaged indexes, such as the Standard & Poor's 500 Com-
            posite Stock Price Index, the Lehman Brothers Aggregate Bond In-
            dex, the Lehman Brothers Mortgage-Backed Securities Index, the
            Merrill Lynch 1 to 3 Year Treasury Index, the Lehman Intermediate
            and 20+ Year Treasury Blend Index, the Lehman BB Intermediate Cor-
            porate Index, indexes prepared by Lipper Analytical Services, the
            J.P. Morgan Global Index, the J.P. Morgan Emerging Markets Bond
            Index Plus, the Salomon Brothers World Government Bond Index-10
            Non U.S.-Dollar Hedged and the J.P. Morgan Government Bond Index
            Non U.S.-
 
36
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Dollar Hedged, and other entities or organizations which track the
            performance of investment companies or investment advisers. Unman-
            aged indexes (i.e., other than Lipper) generally do not reflect
            deductions for administrative and management costs and expenses.
            The Adviser may also report to shareholders or to the public in
            advertisements concerning the performance of the Adviser as ad-
            viser to clients other than the Trust, and on the comparative per-
            formance or standing of the Adviser in relation to other money
            managers. Such comparative information may be compiled or provided
            by independent ratings services or by news organizations. Any per-
            formance information, whether related to the Funds or to the Ad-
            viser, should be considered in light of the Funds' investment ob-
            jectives and policies, characteristics and quality of the Funds'
            portfolios, and the market conditions during the time period indi-
            cated, and should not be considered to be representative of what
            may be achieved in the future. For a description of the methods
            used to determine yield and total return for the Funds, see the
            Statement of Additional Information.
               Investment results of the Funds will fluctuate over time, and
            any presentation of the Funds' total return or yield for any prior
            period should not be considered as a representation of what an in-
            vestor's total return or yield may be in any future period.
 
            How to Buy Shares
 
            Class A, Class B and Class C shares of each Fund of the Trust are
            continuously offered through the Trust's principal underwriter,
            PIMCO Funds Distributors LLC (the "Distributor"), and through
            other firms which have dealer agreements with the Distributor
            ("participating brokers") or which have agreed to act as introduc-
            ing brokers for the Distributor ("introducing brokers").
               There are two ways to purchase Class A, Class B or Class C
            shares: either 1) through your dealer or broker which has a dealer
            agreement with the Distributor; or 2) directly by mailing a PIMCO
            Funds account application (the "account application") with pay-
            ment, as described below under the heading Direct Investment, to
            the Distributor (if no dealer is named in the account application,
            the Distributor may act as dealer).
               Each Fund currently offers and sells three classes of shares in
            this Prospectus (Class A, Class B and Class C). Class A, Class B
            and Class C shares of the Strategic Balanced Fund are not offered
            as of the date of this Prospectus; however, investment opportuni-
            ties in this Fund may be available in the future. Shares may be
            purchased at a price equal to their net asset value per share next
            determined after receipt of an order, plus a sales charge which,
            at the election of the purchaser, may be imposed either (i) at the
            time of the purchase in the case of Class A shares (the "initial
            sales charge alternative"), (ii) on a contingent deferred basis in
            the case of Class B shares (the "deferred sales charge alterna-
            tive"), or (iii) by the deduction of an ongoing asset based sales
            charge in the case of Class C shares (the "asset based sales
            charge alternative"). In certain circumstances, Class A and Class
            C shares are also subject to a CDSC. See "Alternative Purchase Ar-
            rangements." Purchase payments for Class B and Class C shares are
            fully invested at the net asset value next determined after ac-
            ceptance of the trade. Purchase payments for Class A shares, less
            the applicable sales charge, are invested at the net asset value
            next determined after acceptance of the trade.
               All purchase orders received by the Distributor prior to the
            close of regular trading (normally 4:00 p.m., Eastern time) on the
            New York Stock Exchange (the "Exchange"), on a regular business
            day, are processed at that day's offering price. However, orders
            received by the Distributor from dealers or brokers after the of-
            fering price is determined that day will receive such offering
            price if the orders were received by the dealer or broker from its
            customer prior to such determination and were transmitted to and
            received by the Distributor prior to its close of business that
            day (normally 5:00 p.m., Eastern time) or, in the case of certain
            retirement plans, received by the Distributor prior to 9:30 a.m.,
            Eastern time on the next business day. Purchase orders received on
            other than a regular business day will be executed on the next
            succeeding regular business day. The Distributor, in its sole dis-
            cretion, may accept or reject any order for purchase of Fund
            shares. The sale of shares will be suspended during any period in
            which the Exchange is closed for other than weekends or holidays,
            or if permitted by the rules of the Securities and Exchange Com-
            mission, when trading
 
                                                                             37
                                                                    Prospectus
<PAGE>
 
            on the Exchange is restricted or during an emergency which makes
            it impracticable for the Funds to dispose of their securities or
            to determine fairly the value of their net assets, or during any
            other period as permitted by the Securities and Exchange Commis-
            sion for the protection of investors.
               Except for purchases through the PIMCO Funds Auto-Invest plan,
            the PIMCO Funds Auto-Exchange plan, investments pursuant to the
            Uniform Gifts to Minors Act, and tax-qualified and wrap programs
            referred to below under "Tax-Qualified Retirement Plans" and
            "Sales at Net Asset Value", the minimum initial investment in
            Class A, Class B or Class C shares of any Fund of the Trust or any
            series of PIMCO Funds: Multi-Manager Series is $2,500, and the
            minimum additional investment is $100 per Fund. For information
            about dealer commissions, see "Alternative Purchase Arrangements"
            below. Persons selling Fund shares may receive different compensa-
            tion for selling Class A, Class B or Class C shares. Normally,
            Fund shares purchased through participating brokers are held in
            the investor's account with that broker. No share certificates
            will be issued unless specifically requested in writing by an in-
            vestor or broker-dealer.
 
 
DIRECT      Investors who wish to invest in Class A, Class B or Class C shares
INVESTMENT  of the Trust directly, rather than through a participating broker,
            may do so by opening an account with the Distributor. To open an
            account, an investor should complete the account application. All
            shareholders who open direct accounts with the Distributor will
            receive from the Distributor individual confirmations of each pur-
            chase, redemption, dividend reinvestment, exchange or transfer of
            Trust shares, including the total number of Trust shares owned as
            of the confirmation date, except that purchases which result from
            the reinvestment of daily-accrued dividends and/or distributions
            will be confirmed once each calendar quarter. See "Distributions"
            below. Information regarding direct investment or any other fea-
            tures or plans offered by the Trust may be obtained by calling the
            Distributor at 1-800-426-0107 or by calling your broker.
 
 
PURCHASE BY Investors who wish to invest directly may send a check payable to
MAIL        PIMCO Funds Distributors LLC, along with a completed application
            form to:
 
               PIMCO Funds Distributors LLC
               P.O. Box 9688
               Providence, RI 02940-9688
 
               Purchases are accepted subject to collection of checks at full
            value and conversion into federal funds. Payment by a check drawn
            on any member of the Federal Reserve System can normally be con-
            verted into federal funds within two business days after receipt
            of the check. Checks drawn on a non-member bank may take up to 15
            days to convert into federal funds. In all cases, the purchase
            price is based on the net asset value next determined after the
            purchase order and check are accepted, even though the check may
            not yet have been converted into federal funds.
 
 
SUBSEQUENT  Subsequent purchases of Class A, Class B or Class C shares can be
PURCHASES   made as indicated above by mailing a check with a letter describ-
OF SHARES   ing the investment or with the additional investment portion of a
            confirmation statement. Except for subsequent purchases through
            the PIMCO Funds Auto-Invest plan, the PIMCO Funds Auto-Exchange
            plan, tax-qualified programs and PIMCO Funds Fund Link referred to
            below, and except during periods when an Automatic Withdrawal plan
            is in effect, the minimum subsequent purchase is $100 in any Fund.
            All payments should be made payable to PIMCO Funds Distributors
            LLC and should clearly indicate the shareholder's account number.
            Checks should be mailed to the address above under "Purchase by
            Mail."
 
 
TAX-
QUALIFIED   The Distributor makes available retirement plan services and docu-
RETIREMENT  ments for Individual Retirement Accounts (IRAs), including Roth
PLANS       IRAs, for which Boston Safe Deposit & Trust Company serves as
            trustee and for IRA accounts established with Form 5305-SIMPLE un-
            der the Internal Revenue Code of 1986, as amended (the "Code").
            These accounts include Simplified Employee Pension Plan (SEP) and
            Salary Reduction Simplified Employee Pension Plan (SAR/SEP)
 
38
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            IRA accounts and prototype documents. In addition, prototype docu-
            ments are available for establishing 403(b)(7) Custodial Accounts
            with Boston Safe Deposit & Trust Company as custodian. This type
            of plan is available to employees of certain non-profit organiza-
            tions.
               The Distributor also makes available prototype documents for
            establishing Money Purchase and/or Profit Sharing Plans and 401(k)
            Retirement Savings Plans. These prototype plans require certain
            minimum per participant account sizes and certain minimum aggre-
            gate investments in the Trust, but are not subject to the small
            account fees described below that will apply to other plans. In-
            vestors should call the Distributor at 1-800-426-0107 for further
            information about these plans and should consult with their own
            tax advisers before establishing any retirement plan. Investors
            who maintain their accounts with participating brokers should con-
            sult their broker about similar types of accounts that may be of-
            fered through the broker. The minimum initial investment for all
            tax qualified plans (except for employer- sponsored plans, SIMPLE
            IRAs, SEPs and SAR/SEPs) is $1,000 per Fund and the minimum subse-
            quent investment is $100 and the minimum initial investment for
            employer-sponsored plans, SIMPLE IRAs, SEPs and SAR/SEPs and the
            minimum subsequent investment per Fund for all such plans is $50.
 
 
PIMCO FUNDS The PIMCO Funds Auto-Invest plan provides for periodic investments
AUTO-INVEST into the shareholder's account with the Trust by means of auto-
            matic transfers of a designated amount from the shareholder's bank
            account. The minimum investment for eligibility in the PIMCO Funds
            Auto-Invest plan is $1,000 per Fund. Subsequent investments may be
            made monthly or quarterly, and may be in any amount subject to a
            minimum of $50 per month for each Fund in which shares are pur-
            chased through the plan. Further information regarding the PIMCO
            Funds Auto-Invest plan is available from the Distributor or par-
            ticipating brokers. You may enroll by completing the appropriate
            section on the account application, or you may obtain an Auto-In-
            vest application by calling the Distributor or your broker.
 
 
PIMCO FUNDS The PIMCO Funds Auto-Exchange plan establishes regular, periodic
AUTO-       exchanges from one Fund to another Fund or a series of PIMCO
EXCHANGE    Funds: Multi-Manager Series which offers Class A, Class B or Class
            C shares. The plan provides for regular investments into a share-
            holder's account in a specific Fund by means of automatic ex-
            changes of a designated amount from another Fund account of the
            same class of shares and with identical account registration.
               Exchanges may be made monthly or quarterly, and may be in any
            amount subject to a minimum of $1,000 to open a new Fund account
            and of $50 for any existing Fund account for which shares are pur-
            chased through the plan. Further information regarding the PIMCO
            Funds Auto-Exchange plan is available from the Distributor at1-
            800-426-0107 or participating brokers. You may enroll by complet-
            ing an application which may be obtained from the Distributor or
            by telephone request at 1-800-426-0107. For more information on
            exchanges, see "Exchange Privilege."
 
 
PIMCO FUNDS PIMCO Funds Fund Link ("Fund Link") connects your Fund account
FUND LINK   with a bank account. Fund Link may be used for subsequent pur-
            chases and for redemptions and other transactions described under
            "How to Redeem." Purchase transactions are effected by electronic
            funds transfers from the shareholder's account at a U.S. bank or
            other financial institution that is an Automated Clearing House
            ("ACH") member. Investors may use Fund Link to make subsequent
            purchases of shares in amounts from $50 to $10,000. To initiate
            such purchases, call 1-800-426-0107. All such calls will be re-
            corded. Fund Link is normally established within 45 days of re-
            ceipt of a Fund Link application by First Data Investor Services
            Group, Inc. (the "Transfer Agent"). The minimum investment by Fund
            Link is $50 per Fund. Shares will be purchased on the regular
            business day the Distributor receives the funds through the ACH
            system, provided the funds are received before the close of regu-
            lar trading on the Exchange. If the funds are received after the
            close of regular trading, the shares will be purchased on the next
            regular business day.
               Fund Link privileges must be requested on the account applica-
            tion. To establish Fund Link on an existing account, complete a
            Fund Link application, which is available from the Distributor or
            your broker, with signatures guaranteed from all shareholders of
            record for the account. See "Signature Guarantee" below. Such
            privileges apply to each shareholder of record for the account un-
            less and until the Distributor receives written instructions from
            a share-
                                                                    Prospectus
                                                                              39
<PAGE>
 
            holder of record canceling such privileges. Changes of bank ac-
            count information must be made by completing a new Fund Link ap-
            plication signed by all owners of record of the account, with all
            signatures guaranteed. The Distributor, the Transfer Agent and the
            Fund may rely on any telephone instructions believed to be genuine
            and will not be responsible to shareholders for any damage, loss
            or expenses arising out of such instructions. The Fund reserves
            the right to amend, suspend or discontinue Fund Link privileges at
            any time without prior notice. Fund Link does not apply to shares
            held in broker "street name" accounts.
 
 
SIGNATURE   When a signature guarantee is called for, the shareholder should
GUARANTEE   have "Signature Guaranteed" stamped under his signature and guar-
            anteed by any of the following entities: U.S. banks, foreign banks
            having a U.S. correspondent bank, credit unions, savings associa-
            tions, U.S. registered dealers and brokers, municipal securities
            dealers and brokers, government securities dealers and brokers,
            national securities exchanges, registered securities associations
            and clearing agencies (each an "Eligible Guarantor Institution").
            The Distributor reserves the right to reject any signature guaran-
            tee pursuant to its written signature guarantee standards or pro-
            cedures, which may be revised in the future to permit it to reject
            signature guarantees from Eligible Guarantor Institutions that do
            not, based on credit guidelines, satisfy such written standards or
            procedures. The Trust may change the signature guarantee require-
            ments from time to time upon notice to shareholders, which may be
            given by means of a new or supplemented Prospectus.
 
 
ACCOUNT     Changes in registration or account privileges may be made in writ-
REGISTRATIONing to the Transfer Agent. Signature guarantees may be required.
CHANGES     See "Signature Guarantee" above. All correspondence must include
            the account number and must be sent to:
 
                PIMCO Funds Distributors LLC
                P.O. Box 9688
                Providence, RI 02940-9688
 
 
SMALL       Because of the disproportionately high costs of servicing accounts
ACCOUNT FEE with low balances, a fee at an annual rate of $16, paid to Pacific
            Investment Management, the Funds' administrator, will automati-
            cally be deducted from direct accounts with balances falling below
            a minimum level. The valuation of accounts and the deduction are
            expected to take place during the last five days of each calendar
            quarter. The fee will be deducted in quarterly installments from
            accounts with balances below $2,500 except for Uniform Gift to Mi-
            nors, IRA, Roth IRA and Auto-Invest accounts, for which the limit
            is $1,000. Effective April 1, 1999, except for prototype plans de-
            scribed above, the fee will apply to employer-sponsored retirement
            accounts, Money Purchase and/or Profit Sharing plans, 401(k)
            plans, 403(b)(7) custodial accounts, SIMPLE IRAs, SEPs and
            SAR/SEPs. (A separate custodial fee may apply to IRAs, Roth IRAs
            and other retirement accounts.) No fee will be charged on any ac-
            count of a shareholder if the aggregate value of all of the share-
            holder's accounts is at least $50,000. No small account fee will
            be charged to employee and employee-related accounts of PIMCO Ad-
            visors and/or its affiliates.
 
 
MINIMUM     Due to the relatively high cost to the Funds of maintaining small
ACCOUNT     accounts, you are asked to maintain an account balance of at least
SIZE        the amount necessary to open the type of account involved. If your
            balance is below such minimum for three months or longer, the
            Fund's administrator shall have the right (except in the case of
            employer-sponsored retirement accounts) to close your account af-
            ter giving you 60 days in which to increase your balance. Your ac-
            count will not be liquidated if the reduction in size is due
            solely to market decline in the value of your Fund shares or if
            the aggregate value of all your accounts in PIMCO Funds exceeds
            $50,000.
 
 
40
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Alternative Purchase Arrangements
 
            The Trust offers investors three classes of shares in this Pro-
            spectus (Class A, Class B and Class C) which bear sales charges in
            different forms and amounts and which bear different levels of ex-
            penses. Through separate prospectuses, certain of the Funds offer
            up to three additional classes of shares, Class D, Institutional
            Class and Administrative Class shares. Class D shares are offered
            through financial intermediaries. Institutional Class and Adminis-
            trative Class shares are offered to pension and profit sharing
            plans, employee benefit plans, endowments, foundations, corpora-
            tions and other high net worth individuals. Class D, Institutional
            Class and Administrative Class shares are sold without sales
            charges and have different expenses than Class A, Class B and
            Class C shares. As a result of lower sales charges and/or operat-
            ing expenses, Class D, Administrative Class and Institutional
            Class shares are generally expected to achieve higher investment
            returns than Class A, Class B or Class C shares. To obtain more
            information about the other classes of shares, please call the
            Distributor at 1-800-927-4648 (for Institutional and Administra-
            tive Classes) or 1-888-87-PIMCO (for Class D).
               The alternative purchase arrangements offered in this Prospec-
            tus are designed to enable a retail investor to choose the method
            of purchasing Fund shares that is most beneficial to the investor
            based on all factors to be considered, which include: the amount
            and intended length of the investment; the particular Fund; and
            whether the investor intends to exchange shares for shares of
            other Funds. Generally, when making an investment decision, in-
            vestors should consider the anticipated life of an intended in-
            vestment in the Funds, the accumulated distribution and servicing
            fees plus CDSCs
            on Class B or Class C shares, the initial sales charge plus accu-
            mulated servicing fees on Class A shares (plus a CDSC in certain
            circumstances), the possibility that the anticipated higher return
            on Class A shares due to the lower ongoing charges will offset the
            initial sales charge paid on such shares, the automatic conversion
            of Class B shares to Class A shares and the difference in the
            CDSCs applicable to Class A, Class B and Class C shares.
 
            CLASS A The initial sales charge alternative (Class A) might be
            preferred by investors purchasing shares of sufficient aggregate
            value to qualify for reductions in the initial sales charge appli-
            cable to such shares. Similar reductions are not available on the
            contingent deferred sales charge alternative (Class B) or the as-
            set based sales charge alternative (Class C). Class A shares are
            subject to a servicing fee but are not subject to a distribution
            fee and, accordingly, such shares are expected to pay correspond-
            ingly higher dividends on a per share basis. However, because ini-
            tial sales charges are deducted at the time of purchase, not all
            of the purchase payment for Class A shares is invested initially.
            Class B and Class C shares might be preferable to investors who
            wish to have all purchase payments invested initially, although
            remaining subject to higher distribution and servicing fees and,
            for certain periods, being subject to a CDSC. An investor who
            qualifies for an elimination of the Class A initial sales charge
            should also consider whether he or she anticipates redeeming
            shares in a time period which will subject such shares to a CDSC
            as described below. See "Initial Sales Charge Alternative--Class A
            Shares--Class A Deferred Sales Charge" below.
 
            CLASS B Class B shares might be preferred by investors who intend
            to invest in the Funds for longer periods and who do not intend to
            purchase shares of sufficient aggregate value to qualify for sales
            charge reductions applicable to Class A shares. Both Class B and
            Class C shares can be purchased at net asset value without an ini-
            tial sales charge. However, unlike Class C shares, Class B shares
            convert into Class A shares after the shares have been held for
            seven years. After the conversion takes place, the shares will no
            longer be subject to a CDSC, and will be subject to the servicing
            fees charged for Class A shares which are lower than the distribu-
            tion and servicing fees charged on either Class B or Class C
            shares. See "Deferred Sales Charge Alternative--Class B Shares"
            below. Class B shares are not available for purchase by employer
            sponsored retirement plans.
 
            CLASS C Class C shares might be preferred by investors who intend
            to purchase shares which are not of sufficient aggregate value to
            qualify for Class A sales charges of 1% or less and who wish to
            have all purchase payments invested
 
                                                                             41
                                                                    Prospectus
<PAGE>
 
            initially. Class C shares are preferable to Class B shares for in-
            vestors who intend to maintain their investment for intermediate
            periods and therefore may also be preferable for investors who are
            unsure of the intended length of their investment. Unlike Class B
            shares, Class C shares are not subject to a CDSC after they have
            been held for one year and are subject to only a 1% CDSC during
            the first year. However, because Class C shares do not convert
            into Class A shares, Class B shares are preferable to Class C
            shares for investors who intend to maintain their investment in
            the Funds for long periods. See "Asset Based Sales Charge Alterna-
            tive--Class C Shares" below.
               In determining which class of shares to purchase, an investor
            should always consider whether any waiver or reduction of a sales
            charge or a CDSC is available. See generally "Initial Sales Charge
            Alternative--Class A Shares" and "Waiver of Contingent Deferred
            Sales Charges" below.
               The maximum single purchase of Class B shares of the Trust and
            series of PIMCO Funds: Multi-Manager Series accepted is $249,999.
            The maximum single purchase of Class C shares of the Trust and se-
            ries of PIMCO Funds: Multi-Manager Series accepted is $999,999.
            The Funds may refuse any order to purchase shares.
               For a description of the Distribution and Servicing Plans and
            distribution and servicing fees payable thereunder with respect to
            Class A, Class B and Class C shares, see "Distributor and Distri-
            bution and Servicing Plans" below.
 
            WAIVER OF CONTINGENT DEFERRED SALES CHARGES The CDSC applicable to
            Class A and Class C shares is currently waived for (i) any partial
            or complete redemption in connection with (a) required minimum
            distributions to IRA account owners or beneficiaries who are age
            70 1/2 or older or (b) distributions to participants in employer-
            sponsored retirement plans upon attaining age 59 1/2 or on account
            of death or disability;* (ii) any partial or complete redemption
            in connection with a qualifying loan or hardship withdrawal from
            an employer sponsored retirement plan; (iii) any complete redemp-
            tion in connection with a distribution from a qualified employer
            retirement plan in connection with termination of employment or
            termination of the employer's plan and the transfer to another em-
            ployer's plan or to an IRA (with the exception of a Roth IRA);
            (iv) any partial or complete redemption following death or dis-
            ability (as defined in the Code) of a shareholder (including one
            who owns the shares as joint tenant with his or her spouse) from
            an account in which the deceased or disabled is named, provided
            the redemption is requested within one year of the death or ini-
            tial determination of disability; (v) any redemption resulting
            from a return of an excess contribution to a qualified employer
            retirement plan or an IRA (with the exception of a Roth IRA); (vi)
            up to 10% per year of the value of an account which (a) has the
            value of at least $10,000 at the start of such year and (b) is
            subject to an Automatic Withdrawal Plan; (vii) redemptions by
            Trustees, officers and employees of the Trust, and by directors,
            officers and employees of the Distributor and the Adviser; (viii)
            redemptions effected pursuant to a Fund's right to involuntarily
            redeem a shareholder's account if the aggregate net asset value of
            shares held in such shareholder's account is less than a minimum
            account size specified in such Fund's prospectus; (ix) involuntary
            redemptions caused by operation of law; (x) redemption of shares
            of any Fund that is combined with another Fund, investment compa-
            ny, or personal holding company by virtue of a merger, acquisition
            or other similar reorganization transaction; (xi) redemptions by a
            shareholder who is a participant making periodic purchases of not
            less than $50 through certain employer sponsored savings plans
            that are clients of a broker-dealer with which the Distributor has
            an agreement with respect to such purchases; (xii) redemptions ef-
            fected by trustees or other fiduciaries who have purchased shares
            for employer sponsored plans, the trustee, administrator, fiducia-
            ry, broker, trust company or registered investment adviser for
            which has an agreement with the Distributor with respect to such
            purchases; or (xiii) redemptions in connection with IRA accounts
            established with Form 5305-SIMPLE under the Code for which the
            Trust is the designated financial institution.
 
            -------
            *This subsection (i) shall read as follows until December 31,
              1998: "(i) any partial or complete redemption in connection with
              any of the following distributions from a retirement plan,
              including a 403(b)(7) custodial account or an IRA (with the
              exception of a Roth IRA), that qualify for exemption from the
              additional tax on early distributions under Section 72(t) of the
              Code: (a) upon attaining age 59 1/2, (b) on account of death or
              disability, (c) as part of a series of substantially equal
              periodic payments, (d) in the case of an IRA (with the exception
              of a Roth IRA), attributable to qualified higher education
              expenses or to qualified first-time home-buyer expenses or (e)
              in the case of a retirement plan other than an IRA, upon
              separation from service after attaining age 55;"
 
42
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               The CDSC applicable to Class B shares is currently waived for
            any partial or complete redemption in each of the following cases:
            (a) in connection with required minimum distributions to IRA ac-
            count owners or to plan participants or beneficiaries who are age
            70 1/2 or older; (b) following death or disability (as defined in
            the Code) of a shareholder (including one who owns the shares as
            joint tenant with his or her spouse) from an account in which the
            deceased or disabled is named, provided the redemption is re-
            quested within one year of the death or initial determination of
            disability; and (c) up to 10% per year of the value of an account
            which (i) has a value of at least $100,000 at the start of such
            year and (ii) is subject to an Automatic Withdrawal Plan. See "How
            to Redeem--Automatic Withdrawal Plan."
               The Distributor may require documentation prior to waiver of
            the CDSC for any class, including distribution letters, certifica-
            tion by plan administrators, applicable tax forms, death certifi-
            cates, physicians' certificates, etc.
 
                                                                    Prospectus
                                                                              43
<PAGE>
 
 
 
INITIAL
SALES
CHARGE
ALTERNATIVE --
            Class A shares are sold at a public offering price equal to their
            net asset value per share plus a sales charge, as set forth below.
            As indicated below under "Class A Deferred Sales Charge," certain
            investors that purchase $1,000,000 ($250,000 in the case of the
CLASS A     Short-Term Fund) or more of any Fund's Class A shares (and thus
SHARES      pay no initial sales charge) may be subject to a 1% CDSC if they
            redeem such shares during the first 18 months after their pur-
            chase.
 
 
              TOTAL RETURN, HIGH YIELD, LONG-TERM U.S. GOVERNMENT, GLOBAL BOND
              II, FOREIGN BOND, EMERGING MARKETS BOND AND STRATEGIC BALANCED
              FUNDS
 
<TABLE>
<CAPTION>
                                SALES CHARGE                    DISCOUNT OR
                                AS % OF NET  SALES CHARGE       COMMISSION TO
           AMOUNT OF            AMOUNT       AS % OF THE PUBLIC DEALERS AS % OF
           PURCHASE             INVESTED     OFFERING PRICE     PUBLIC OFFERING PRICE
              -----------------------------------------------------------------------
           <S>                  <C>          <C>                <C>
           $0 - $49,999         4.71%        4.50%              4.00%
              -----------------------------------------------------------------------
           $50,000 - $99,999    4.17%        4.00%              3.50%
              -----------------------------------------------------------------------
           $100,000 - $249,999  3.63%        3.50%              3.00%
              -----------------------------------------------------------------------
           $250,000 - $499,999  2.56%        2.50%              2.00%
              -----------------------------------------------------------------------
           $500,000 - $999,999  2.04%        2.00%              1.75%
              -----------------------------------------------------------------------
           $1,000,000+          0.00%(/1/)   0.00%(/1/)         0.50%(/2/)
</TABLE>
 
 
              LOW DURATION, REAL RETURN BOND, MUNICIPAL BOND AND STOCKSPLUS
              FUNDS
 
<TABLE>
<CAPTION>
                                SALES CHARGE                    DISCOUNT OR
                                AS % OF NET  SALES CHARGE       COMMISSION TO
           AMOUNT OF            AMOUNT       AS % OF THE PUBLIC DEALERS AS % OF
           PURCHASE             INVESTED     OFFERING PRICE     PUBLIC OFFERING PRICE
              -----------------------------------------------------------------------
           <S>                  <C>          <C>                <C>
           $0 - $49,999         3.09%        3.00%              2.50%
              -----------------------------------------------------------------------
           $50,000 - $99,999    2.56%        2.50%              2.00%
              -----------------------------------------------------------------------
           $100,000 - $249,999  2.04%        2.00%              1.75%
              -----------------------------------------------------------------------
           $250,000 - $499,999  1.52%        1.50%              1.25%
              -----------------------------------------------------------------------
           $500,000 - $999,999  1.27%        1.25%              1.00%
              -----------------------------------------------------------------------
           $1,000,000+          0.00%(/1/)   0.00%(/1/)         0.50%(/2/)
</TABLE>
 
 
 
              SHORT-TERM FUND
 
<TABLE>
<CAPTION>
                                SALES CHARGE                    DISCOUNT OR
                                AS % OF NET  SALES CHARGE       COMMISSION TO
           AMOUNT OF            AMOUNT       AS % OF THE PUBLIC DEALERS AS % OF
           PURCHASE             INVESTED     OFFERING PRICE     PUBLIC OFFERING PRICE
              -----------------------------------------------------------------------
           <S>                  <C>          <C>                <C>
           $0 - $49,999         2.04%        2.00%              1.75%
              -----------------------------------------------------------------------
           $50,000 - $99,999    1.78%        1.75%              1.50%
              -----------------------------------------------------------------------
           $100,000 - $249,999  1.52%        1.50%              1.25%
              -----------------------------------------------------------------------
           $250,000+            0.00%(/1/)   0.00%(/1/)         0.25%(/2/)
</TABLE>
 
            1. As shown, investors that purchase more than $1,000,000 of any
            Fund's Class A shares ($250,000 in the case of the Short-Term
            Fund) will not pay any initial sales charge on such purchase. How-
            ever, except with regard to purchases of Class A shares of the
            Money Market Fund, purchasers of $1,000,000 ($250,000 in the case
            of the Short-Term Fund) or more of Class A shares (other than
            those purchasers described below under "Sales at Net Asset Value"
            where no commission is paid) will be subject to a CDSC of 1% if
            such shares are redeemed during the first 18 months after such
            shares are purchased unless such purchaser is eligible for a
            waiver of the CDSC as described under "Waiver of Contingent De-
            ferred Sales Charges" above. See "Class A Deferred Sales Charge"
            below.
 
            2. The Distributor will pay a commission to dealers who sell
            amounts of $1,000,000 ($250,000 in the case of the Short-Term
            Fund) or more of Class A shares (or who sell Class A shares at net
            asset value to certain employer-sponsored plans as outlined in
            "Sales at Net Asset Value") of each of the Funds except for the
            Money Market Fund (for which no payment is made) and the Short-
            Term Fund, according to the following schedule: 0.50% of the first
            $2,000,000 and 0.25% of amounts over $2,000,000; and 0.25% of
            sales of Class A shares of the Short-Term Fund in excess of
            $250,000.
 
               No initial sales charge applies to purchases of Class A shares
            of the Money Market Fund. However, if a shareholder exchanges
            Class A shares of the Money Market Fund, for which no sales load
            was paid at the time of purchase, for Class A shares of any other
            Fund, the sales charge shown above for the other Fund applies at
            the time of the exchange.
 
44
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               Each Fund receives the entire net asset value of its Class A
            shares purchased by investors. The Distributor receives the sales
            charge shown above less any applicable discount or commission
            "reallowed" to participating brokers in the amounts indicated in
            the table above. The Distributor may, however, elect to reallow
            the entire sales charge to participating brokers for all sales
            with respect to which orders are placed with the Distributor for
            any particular Fund during a particular period. During such peri-
            ods as may from time to time be designated by the Distributor, the
            Distributor will pay an additional amount of up to .50% of the
            purchase price on sales of Class A shares of all or selected Funds
            purchased to each participating broker which obtains purchase or-
            ders in amounts exceeding thresholds established from time to time
            by the Distributor. From time to time, the Distributor, its parent
            and/or its affiliates may make additional payments to one or more
            participating brokers based upon factors such as the level of
            sales or the length of time clients' assets have remained in the
            Trust.
               Shares issued pursuant to the automatic reinvestment of income
            dividends or capital gains distributions are issued at net asset
            value and are not subject to any sales charges.
               Under the circumstances described below, investors may be enti-
            tled to pay reduced sales charges for Class A shares.
 
            COMBINED PURCHASE PRIVILEGE Investors may qualify for a reduced
            sales charge by combining purchases of the Class A shares of one
            or more Funds or series of PIMCO Funds: Multi-Manager Series which
            offer Class A shares (together, "eligible PIMCO Funds") into a
            "single purchase," if the resulting purchase totals at least
            $50,000. The term single purchase refers to:
                (i)   a single purchase by an individual, or concurrent
                      purchases, which in the aggregate are at least equal to
                      the prescribed amounts, by an individual, his or her
                      spouse and their children under the age of 21 years
                      purchasing Class A shares of the eligible PIMCO Funds
                      for his, her or their own account;
                (ii)  a single purchase by a trustee or other fiduciary
                      purchasing shares for a single trust, estate or
                      fiduciary account although more than one beneficiary is
                      involved; or
                (iii) a single purchase for the employee benefit plans of a
                      single employer.
            For further information, call the Distributor at 1-800-426-0107 or
            your broker.
 
            CUMULATIVE QUANTITY DISCOUNT (RIGHT OF ACCUMULATION) A purchase of
            additional Class A shares of any eligible PIMCO Fund may qualify
            for a Cumulative Quantity Discount at the rate applicable to the
            discount bracket obtained by adding:
                (i)   the investor's current purchase;
                (ii)  the value (at the close of business on the day of the
                      current purchase) of all Class A shares of any eligible
                      PIMCO Fund (other than the Money Market Fund) held by
                      the investor computed at the maximum offering price; and
                (iii) the value of all shares described in paragraph (ii)
                      owned by another shareholder eligible to be combined
                      with the investor's purchase into a "single purchase" as
                      defined above under "Combined Purchase Privilege."
              For example, if you owned Class A shares of the Total Return
            Fund worth $25,000 at the current maximum offering price and
            wished to purchase Class A shares of the Global Bond Fund II worth
            an additional $30,000, the sales charge for the $30,000 purchase
            would be at the 4.00% rate applicable to a single $55,000 purchase
            of shares of the Global Bond Fund II, rather than the 4.50% rate.
 
            LETTER OF INTENT An investor may also obtain a reduced sales
            charge by means of a written Letter of Intent, which expresses an
            intention to invest not less than $50,000 within a period of 13
            months in Class A shares of any eligible PIMCO Fund(s) (other than
            the Money Market Fund). Each purchase of shares under a Letter of
            Intent will be made at the public offering price or prices appli-
            cable at the time of such purchase to a single transaction of the
            dollar amount indicated in the Letter. At the investor's option, a
            Letter of Intent may include purchases of Class A shares of any
            eligible PIMCO Fund (other than the Money Market Fund) made not
            more than 90 days prior to the date the Letter of
 
                                                                             45
                                                                    Prospectus
<PAGE>
 
            Intent is signed; however, the 13-month period during which the
            Letter is in effect will begin on the date of the earliest pur-
            chase to be included and the sales charge on any purchases prior
            to the Letter will not be adjusted.
               Investors qualifying for the Combined Purchase Privilege de-
            scribed above may purchase shares of the eligible PIMCO Funds un-
            der a single Letter of Intent. For example, if at the time you
            sign a Letter of Intent to invest at least $100,000 in Class A
            shares of any Fund (other than the Money Market Fund), you and
            your spouse each purchase Class A shares of the Global Bond Fund
            II worth $30,000 (for a total of $60,000), it will only be neces-
            sary to invest a total of $40,000 during the following 13 months
            in Class A shares of any of the Funds (other than the Money Market
            Fund) to qualify for the 3.50% sales charge on the total amount
            being invested (the sales charge applicable to an investment of
            $100,000 in any of the Funds other than the Money Market, Short-
            Term, Low Duration, Real Return Bond, Municipal Bond and
            StocksPLUS Funds).
               A Letter of Intent is not a binding obligation to purchase the
            full amount indicated. The minimum initial investment under a Let-
            ter of Intent is 5% of such amount. Shares purchased with the
            first 5% of such amount will be held in escrow (while remaining
            registered in your name) to secure payment of the higher sales
            charge applicable to the shares actually purchased in the event
            the full intended amount is not purchased. If the full amount in-
            dicated is not purchased, a sufficient amount of such escrowed
            shares will be involuntarily redeemed to pay the additional sales
            charge applicable to the amount actually purchased, if necessary.
            Dividends on escrowed shares, whether paid in cash or reinvested
            in additional eligible PIMCO Fund shares, are not subject to es-
            crow. When the full amount indicated has been purchased, the es-
            crow will be released.
               If you wish to enter into a Letter of Intent in conjunction
            with your initial investment in Class A shares of a Fund, you
            should complete the appropriate portion of the account
            application. If you are a current Class A shareholder desiring to
            do so you can obtain a form of Letter of Intent by contacting the
            Distributor at 800-426-0107 or any broker participating in this
            program.
 
            REINSTATEMENT PRIVILEGE A Class A shareholder who has caused any
            or all of his shares (other than Money Market Fund shares that
            were not acquired by exchanging Class A shares of another Fund) to
            be redeemed may reinvest all or any portion of the redemption pro-
            ceeds in Class A shares of any eligible PIMCO Fund at net asset
            value without any sales charge, provided that such reinvestment is
            made within 120 calendar days after the redemption or repurchase
            date. Shares are sold to a reinvesting shareholder at the net as-
            set value next determined. See "How Net Asset Value is Deter-
            mined." A reinstatement pursuant to this privilege will not cancel
            the redemption transaction and, consequently, any gain or loss so
            realized may be recognized for federal tax purposes except that no
            loss may be recognized to the extent that the proceeds are rein-
            vested in shares of the same Fund within 30 days. The reinstate-
            ment privilege may be utilized by a shareholder only once, irre-
            spective of the number of shares redeemed, except that the privi-
            lege may be utilized without limit in connection with transactions
            whose sole purpose is to transfer a shareholder's interest in a
            Fund to his Individual Retirement Account or other qualified re-
            tirement plan account. An investor may exercise the reinstatement
            privilege by written request sent to the Distributor or to the in-
            vestor's broker.
 
            SALES AT NET ASSET VALUE Each Fund may sell its Class A shares at
            net asset value without a sales charge to (a) current or retired
            officers, trustees, directors or employees of the Trust, the Ad-
            viser or the Distributor, a parent, brother or sister of any such
            officer, trustee, director or employee or a spouse or child of any
            of the foregoing persons, or any trust, profit sharing or pension
            plan for the benefit of any such person and to any other person if
            the Distributor anticipates that there will be minimal sales ex-
            penses associated with the sale, (b) current or retired trustees
            of PIMCO Funds: Multi-Manager Series, a registered investment com-
            pany for which PIMCO Advisors L.P., an affiliate of the Adviser,
            acts as investment adviser, (c) current registered representatives
            and other full-time employees of participating brokers or such
            persons' spouses or for trust or custodial accounts for their mi-
            nor children, (d) trustees or other fiduciaries purchasing shares
            for certain plans sponsored by employers, professional organiza-
            tions or associations, or charitable organizations, the trustee,
            administrator, fiduciary, broker, trust company or registered in-
            vestment adviser for which has
 
46
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            an agreement with the Distributor with respect to such purchases
            (including provisions related to minimum levels of investment in
            the Trust), and to participants in such plans and their spouses
            purchasing for their accounts(s) or IRAs (with the exception of
            Roth IRAs), (e) participants investing through accounts known as
            "wrap accounts" established with brokers or dealers approved by
            the Distributor where such brokers or dealers are paid a single,
            inclusive fee for brokerage and investment management services,
            (f) client accounts of broker-dealers or registered investment ad-
            visers affiliated with such broker-dealers with which the Distrib-
            utor has an agreement for the use of PIMCO Funds in particular in-
            vestment products or programs, and (g) accounts for which a trust
            company affiliated with the Trust or the Adviser serves as trustee
            or custodian. As described above, the Distributor will not pay any
            initial commission to dealers upon the sale of Class A shares to
            the purchasers described in this paragraph except for sales to
            purchasers described under (d) in this paragraph.
 
            NOTIFICATION OF DISTRIBUTOR An investor or participating broker
            must notify the Distributor whenever a quantity discount or re-
            duced sales charge is applicable to a purchase and must provide
            the Distributor with sufficient information at the time of pur-
            chase to verify that each purchase qualifies for the privilege or
            discount. Upon such notification, the investor will receive the
            lowest applicable sales charge. The quantity discounts described
            above may be modified or terminated at any time.
 
            CLASS A DEFERRED SALES CHARGE For all Funds except the Money Mar-
            ket Fund, investors who purchase $1,000,000 ($250,000 in the case
            of the Short-Term Fund) or more of Class A shares (and, thus, pur-
            chase such shares without any initial sales charge) may be subject
            to a 1% CDSC (the "Class A CDSC") if such shares are redeemed
            within 18 months of their purchase. The Class A CDSC does not ap-
            ply to investors purchasing $1,000,000 or more of any Fund's Class
            A shares ($250,000 in the case of the Short-Term Fund) if such in-
            vestors are otherwise eligible to purchase Class A shares without
            any sales charge because they are described under "Sales at Net
            Asset Value" above.
               For purchases subject to the Class A CDSC, a 1% CDSC will apply
            for any redemption of such Class A shares that occurs within 18
            months of their purchase. No CDSC will be imposed if the shares
            redeemed have been acquired through the reinvestment of dividends
            or capital gains distributions or if the amount redeemed is de-
            rived from increases in the value of the account above the amount
            of purchase payments subject to the CDSC. In determining whether a
            CDSC is payable, it is assumed that Class A shares acquired
            through the reinvestment of dividends and distributions are re-
            deemed first, and thereafter that Class A shares that have been
            held by an investor for the longest period of time are redeemed
            first.
               The Class A CDSC does not apply to Class A shares of the Money
            Market Fund but, if Money Market Fund Class A shares are purchased
            in a transaction that, for any other Fund, would be subject to the
            CDSC (i.e., a purchase of $1,000,000 ($250,000 in the case of the
            Short-Term Fund) or more) and are subsequently exchanged for Class
            A shares of any other Fund, a Class A CDSC will apply to the
            shares of the Fund acquired by exchange for a period of 18 months
            from the date of the exchange.
               The Class A CDSC is currently waived in connection with certain
            redemptions as described above under "Alternative Purchase Ar-
            rangements--Waiver of Contingent Deferred Sales Charges." For more
            information about the Class A CDSC, call the Distributor at 1-800-
            426-0107.
 
            PARTICIPATING BROKERS Investment dealers and other financial in-
            termediaries provide varying arrangements for their clients to
            purchase and redeem Fund shares. Some may establish higher minimum
            investment requirements than set forth above. Firms may arrange
            with their clients for other investment or administrative services
            and may independently establish and charge transaction fees and/or
            other additional amounts to their clients for such services, which
            charges would reduce clients' return. Firms also may hold Fund
            shares in nominee or street name as agent for and on behalf of
            their customers. In such instances, the Trust's transfer agent
            will have no information with respect to or control
                                                                    Prospectus
                                                                              47
<PAGE>
 
            over accounts of specific shareholders. Such shareholders may ob-
            tain access to their accounts and information about their accounts
            only from their broker. In addition, certain privileges with re-
            spect to the purchase and redemption of shares or the reinvestment
            of dividends may not be available through such firms. Some firms
            may participate in a program allowing them access to their cli-
            ents' accounts for servicing including, without limitation, trans-
            fers of registration and dividend payee changes; and may perform
            functions such as generation of confirmation statements and dis-
            bursement of cash dividends. This Prospectus should be read in
            connection with such firms' material regarding their fees and
            services.
 
 
DEFERRED
SALES
CHARGE
ALTERNATIVE --
CLASS B
SHARES
            Class B shares are sold at their current net asset value without
            any initial sales charge. The full amount of an investor's pur-
            chase payment will be invested in shares of the Fund(s) selected.
            A CDSC will be imposed on Class B shares of all Funds if an in-
            vestor redeems an amount which causes the current value of the in-
            vestor's account for a Fund to fall below the total dollar amount
            of purchase payments subject to the CDSC, except that no CDSC is
            imposed if the shares redeemed have been acquired through the re-
            investment of dividends or capital gains distributions or if the
            amount redeemed is derived from increases in the value of the ac-
            count above the amount of purchase payments subject to the CDSC.
               Class B shares of the Short-Term Fund and the Money Market Fund
            are not offered for initial purchase but may be obtained through
            exchanges of Class B shares of other Funds. See "Exchange Privi-
            lege" below. Class B shares are not available for purchase by em-
            ployer sponsored retirement plans.
               Whether a CDSC is imposed and the amount of the CDSC will de-
            pend on the number of years since the investor made a purchase
            payment from which an amount is being redeemed. Purchases are sub-
            ject to the CDSC according to the following schedule:
 
 
<TABLE>
<CAPTION>
           YEAR SINCE PURCHASE   PERCENTAGE CONTINGENT
           PAYMENT WAS MADE      DEFERRED SALES CHARGE
              ----------------------------------------
           <S>                   <C>
           First                   5%
              ----------------------------------------
           Second                  4
              ----------------------------------------
           Third                   3
              ----------------------------------------
           Fourth                  3
              ----------------------------------------
           Fifth                   2
              ----------------------------------------
           Sixth                   1
              ----------------------------------------
           Seventh                 0*
</TABLE>
 
            *After the seventh year,
            Class B shares convert into
            Class A shares as described
            below.
 
               In determining whether a CDSC is payable, it is assumed that
            the purchase payment from which a redemption is made is the earli-
            est purchase payment from which a redemption or exchange has not
            already been fully effected.
               The following example will illustrate the operation of the
            Class B CDSC:
               Assume that an individual opens an account and makes a purchase
            payment of $10,000 for Class B shares of a Fund (except the Money
            Market and Short-Term Funds) and that six months later the value
            of the investor's account for that Fund has grown through invest-
            ment performance and reinvestment of distributions to $11,000. The
            investor then may redeem up to $1,000 from that Fund ($11,000 mi-
            nus $10,000) without incurring a CDSC. If the investor should re-
            deem $3,000, a CDSC would be imposed on $2,000 of the redemption
            (the amount by which the investor's account for the Fund was re-
            duced below the amount of the purchase payment). At the rate of
            5%, the Class B CDSC would be $100.
               In determining whether an amount is available for redemption
            without incurring a CDSC, the purchase payments made for all Class
            B shares in the shareholder's account with the particular Fund are
            aggregated, and the current
 
48
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            value of all such shares is aggregated. Any CDSC imposed on a re-
            demption of Class B shares is paid to the Distributor.
               Class B shares are subject to higher distribution fees than
            Class A shares for a fixed period after their purchase, after
            which they automatically convert to Class A shares and are no
            longer subject to such higher distribution fees. Class B shares of
            each Fund automatically convert into Class A shares after they
            have been held for seven years.
               For sales of Class B shares made and services rendered to Class
            B shareholders, the Distributor intends to make payments to par-
            ticipating brokers, at the time a shareholder purchases Class B
            shares, of 4% of the purchase amount for each of the Funds. During
            such periods as may from time to time be designated by the Dis-
            tributor, the Distributor will pay selected participating brokers
            an additional amount of up to .50% of the purchase price on sales
            of Class B shares of all or selected Funds purchased to each par-
            ticipating broker which obtains purchase orders in amounts exceed-
            ing thresholds established from time to time by the Distributor.
               The Class B CDSC is currently waived in connection with certain
            redemptions as described above under "Alternative Purchase Ar-
            rangements--Waiver of Contingent Deferred Sales Charges." For more
            information about the Class B CDSC, call the Distributor at 1-800-
            426-0107.
 
 
ASSET BASED
SALES
CHARGE
ALTERNATIVE --
CLASS C
SHARES
            Class C shares are sold at their current net asset value without
            any initial sales charge. A CDSC is imposed on Class C shares of
            all Funds if an investor redeems an amount which causes the cur-
            rent value of the investor's account for a Fund to fall below the
            total dollar amount of purchase payments subject to the CDSC, ex-
            cept that no CDSC is imposed if the shares redeemed have been ac-
            quired through the reinvestment of dividends or capital gains dis-
            tributions or if the amount redeemed is derived from increases in
            the value of the account above the amount of purchase payments
            subject to the CDSC. All of an investor's purchase payments are
            invested in shares of the Fund(s) selected.
               Whether a CDSC is imposed and the amount of the CDSC will de-
            pend on the number of years since the investor made a purchase
            payment from which an amount is being redeemed. Purchases are sub-
            ject to the CDSC according to the following schedule:
 
 
<TABLE>
<CAPTION>
           YEAR SINCE PURCHASE   PERCENTAGE CONTINGENT
           PAYMENT WAS MADE      DEFERRED SALES CHARGE
              ----------------------------------------
           <S>                   <C>
           First                   1
              ----------------------------------------
           Thereafter              0
</TABLE>
 
 
               In determining whether a CDSC is payable, it is assumed that
            the purchase payment from which the redemption is made is the ear-
            liest purchase payment (from which a redemption or exchange has
            not already been effected).
               The following example will illustrate the operation of the
            Class C CDSC:
               Assume that an individual opens an account and makes a purchase
            payment of $10,000 for Class C shares of a Fund and that six
            months later the value of the investor's account for that Fund has
            grown through investment performance and reinvestment of distribu-
            tions to $11,000. The investor then may redeem up to $1,000 from
            that Fund ($11,000 minus $10,000) without incurring a CDSC. If the
            investor should redeem $3,000, a CDSC would be imposed on $2,000
            of the redemption (the amount by which the investor's account for
            the Fund was reduced below the amount of the purchase payment). At
            the rate of 1%, the Class C CDSC would be $20.
               In determining whether an amount is available for redemption
            without incurring a CDSC, the purchase payments made for all Class
            C shares in the shareholder's account with the particular Fund are
            aggregated, and the current value of all such shares is aggregat-
            ed. Any CDSC imposed on a redemption of Class C shares is paid to
            the Distributor. Unlike Class B shares, Class C shares do not au-
            tomatically convert to any other class of shares of the Funds.
               Except as described below, for sales of Class C shares made and
            services rendered to Class C shareholders, the Distributor expects
            to make payments to participating brokers, at the time the share-
            holder purchases Class C shares, of 1.00% (representing .75% dis-
            tribution fees and .25% servicing fees) of the purchase amount for
            all Funds except the
                                                                    Prospectus
                                                                              49
<PAGE>
 
            Money Market, Short-Term, Low Duration, Real Return Bond, Munici-
            pal Bond and StocksPLUS Funds. For the Low Duration, Real Return
            Bond, Municipal Bond and StocksPLUS Funds, the Distributor expects
            to make payments of .75% (representing .50% distribution fees and
            .25% service fees); for the Short-Term Fund, the Distributor ex-
            pects to make payments of .55% (representing .30% distribution
            fees and .25% service fees); and for the Money Market Fund, the
            Distributor expects to make no payment. For sales of Class C
            shares made to participants making periodic purchases of not less
            than $50 through certain employer sponsored savings plans which
            are clients of a broker-dealer with which the Distributor has an
            agreement with respect to such purchases, no payments are made at
            the time of purchase. During such periods as may from time to time
            be designated by the Distributor, the Distributor will pay an ad-
            ditional amount of up to .50% of the purchase price on sales of
            Class C shares of all or selected Funds purchased to each partici-
            pating broker which obtains purchase orders in amounts exceeding
            thresholds established from time to time by the Distributor.
               The Class C CDSC is currently waived in connection with certain
            redemptions as described above under "Alternative Purchase Ar-
            rangements--Waiver of Contingent Deferred Sales Charges." For more
            information about the Class C CDSC, contact the Distributor at 1-
            800-426-0107.
 
            Exchange Privilege
 
            A shareholder may exchange Class A, Class B and Class C shares of
            any Fund for the same Class of shares of any other Fund in an ac-
            count with identical registration on the basis of their respective
            net asset values (except that a sales charge will apply on ex-
            changes of Class A shares of the Money Market Fund on which no
            sales charge was paid at the time of purchase). Class A, Class B
            and Class C shares of each Fund may also be exchanged for shares
            of the same class of a series which offers such classes (except
            for the Opportunity Fund if a restriction applies) of PIMCO Funds:
            Multi-Manager Series (including the PIMCO Funds Asset Allocation
            Series portfolios, which are so-called "funds-of-funds" portf-
            olios), an affiliated mutual fund family composed primarily of eq-
            uity portfolios managed by the subsidiary partnerships of PIMCO
            Advisors L.P. Class A shares of the Money Market Fund may be ex-
            changed for Class A shares of any other Fund, but the usual sales
            charges applicable to investments in such other Fund apply on
            shares for which no sales load was paid at the time of purchase.
            There are currently no exchange fees or charges. Exchanges of
            shares outstanding on September 30, 1998 may be made in any amount
            through December 31, 1998 into any portfolio of PIMCO Funds Asset
            Allocation Series. All other exchanges, including exchanges from
            PIMCO Funds Asset Allocation Series portfolios into the Funds or
            series of PIMCO Funds: Multi-Manager Series are subject to the
            $2,500 minimum initial purchase requirement for each Fund, except
            with respect to tax-qualified programs and exchanges effected
            through the PIMCO Funds Auto-Exchange plan. An exchange will con-
            stitute a taxable sale for federal income tax purposes.
               Investors who maintain their account with the Distributor may
            exchange shares by a written exchange request sent to PIMCO Funds
            Distributors LLC, P.O. Box 9688, Providence, RI 02940-9688 or, un-
            less the investor has specifically declined telephone exchange
            privileges on the account application or elected in writing not to
            utilize telephone exchanges, by a telephone request to the Trans-
            fer Agent at 1-800-426-0107. The Trust will employ reasonable pro-
            cedures to confirm that instructions communicated by telephone are
            genuine, and may be liable for any losses due to unauthorized or
            fraudulent instructions if it fails to employ such procedures. The
            Trust will require a form of personal identification prior to act-
            ing on a caller's telephone instructions, will provide written
            confirmations of such transactions and will record telephone in-
            structions. Exchange forms are available from the Distributor at
            1-800-426-0107 and may be used if there will be no change in the
            registered name or address of the shareholder. Changes in regis-
            tration information or account privileges may be made in writing
            to the Transfer Agent, First Data Investor Services Group, Inc.,
            P.O. Box 9688, Providence, RI 02940-9688, or by use of forms which
            are available from the Distributor. A signature guarantee is re-
            quired. See "How to Buy Shares--Signature Guarantee." Telephone
            exchanges may be made between 9:00 a.m., Eastern time and the
            close of regular trading (normally 4:00 p.m., Eastern time) on the
            Exchange on any day the Exchange is open
 
50
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            (generally weekdays other than normal holidays). The Trust re-
            serves the right to refuse exchange purchases if, in the judgment
            of the Adviser, the purchase would adversely affect the Fund and
            its shareholders. In particular, a pattern of exchanges character-
            istic of "market-timing" strategies may be deemed by the Adviser
            to be detrimental to the Trust or a particular Fund. Currently,
            the Trust limits the number of "round trip" exchanges an investor
            may make. An investor makes a "round trip" exchange when the in-
            vestor purchases shares of a particular Fund, subsequently ex-
            changes these shares for shares of a different Fund and then ex-
            changes back into the originally purchased Fund. The Trust has the
            right to refuse any exchange for any investor who completes (by
            making the exchange back into the shares of the originally pur-
            chased Fund) more than six round trip exchanges in any twelve-
            month period. Although the Trust has no current intention of ter-
            minating or modifying the exchange privilege other than as set
            forth in the preceding sentence, it reserves the right to do so at
            any time. Except as otherwise permitted by Securities and Exchange
            Commission regulations, the Trust will give 60 days' advance no-
            tice to shareholders of any termination or material modification
            of the exchange privilege. For further information about exchange
            privileges, contact your participating broker or call the Transfer
            Agent at 1-800-426-0107.
               With respect to Class B and Class C shares, or Class A shares
            subject to a CDSC, if less than all of an investment is exchanged
            out of a Fund, any portion of the investment attributable to capi-
            tal appreciation and/or reinvested dividends or capital gains dis-
            tributions will be exchanged first, and thereafter any portions
            exchanged will be from the earliest investment made in the Fund
            from which the exchange was made. Shareholders should take into
            account the effect of any exchange on the applicability of any
            CDSC that may be imposed upon any subsequent redemption. Although
            the Class A CDSC does not apply to Class A shares of the Money
            Market Fund, Class A shares purchased in a transaction that would
            otherwise be subject to the Class A CDSC (i.e., most purchases of
            $1,000,000 or more) are subsequently exchanged for Class A shares
            of any other Fund, a Class A CDSC will apply to the shares of the
            Fund acquired by exchange for a period of 18 months from the date
            of the exchange. See "Initial Sales Charge Alternative--Class A
            Shares--Class A Deferred Sales Charge" above.
               Investors may also select the PIMCO Funds Auto-Exchange plan
            which establishes automatic periodic exchanges. For further infor-
            mation on automatic exchanges see "How to Buy Shares--PIMCO Funds
            Auto-Exchange" above.
 
            How to Redeem
 
            Class A, Class B or Class C shares may be redeemed through a par-
            ticipating broker, by telephone, by submitting a written redemp-
            tion request directly to the Transfer Agent (for non-broker ac-
            counts), or through an Automatic Withdrawal Plan or PIMCO Funds
            Fund Link.
               A CDSC may apply to a redemption of Class A, Class B or Class C
            shares. See "Alternative Purchase Arrangements" above. Shares are
            redeemed at their net asset value next determined after a proper
            redemption request has been received, less any applicable CDSC.
            There is no charge by the Distributor (other than an applicable
            CDSC) with respect to a redemption; however, a participating bro-
            ker who processes a redemption for an investor may charge custom-
            ary commissions for its services. Dealers and other financial
            services firms are obligated to transmit orders promptly. Requests
            for redemption received by dealers or other firms prior to the
            close of regular trading (normally 4:00 p.m., Eastern time) on the
            Exchange on a regular business day and received by the Distributor
            prior to the close of the Distributor's business day will be con-
            firmed at the net asset value effective as of the closing of the
            Exchange on that day, less any applicable CDSC.
 
 
DIRECT
REDEMPTION  A shareholder's original account application permits the share-
            holder to redeem by written request and by telephone (unless the
            shareholder specifically elects not to utilize telephone redemp-
            tions) and to elect one or more of the additional redemption pro-
            cedures described below. A shareholder may change the instructions
            indicated on his original account application, or may request ad-
            ditional redemption options, only by transmitting a written direc-
            tion to the
 
                                                                             51
                                                                    Prospectus
<PAGE>
 
            Transfer Agent. Requests to institute or change any of the addi-
            tional redemption procedures will require a signature guarantee.
               Redemption proceeds will normally be mailed to the redeeming
            shareholder within seven days or, in the case of wire transfer or
            Fund Link redemptions, sent to the designated bank account within
            one business day. Fund Link redemptions may be received by the
            bank on the second or third business day. In cases where shares
            have recently been purchased by personal check, redemption pro-
            ceeds may be withheld until the check has been collected, which
            may take up to 15 days. To avoid such withholding, investors
            should purchase shares by certified or bank check or by wire
            transfer.
 
 
WRITTEN     To redeem shares in writing (whether or not represented by certif-
REQUESTS    icates), a shareholder must send the following items to the Trans-
            fer Agent, First Data Investor Services Group, Inc., P.O. Box
            9688, Providence, RI 02940-9688.
                (1) a written request for redemption signed by all registered
                    owners exactly as the account is registered on the
                    Transfer Agent's records, including fiduciary titles, if
                    any, and specifying the account number and the dollar
                    amount or number of shares to be redeemed;
                (2) for certain redemptions described below, a guarantee of
                    all signatures on the written request or on the share
                    certificate or accompanying stock power, if required, as
                    described under "How to Buy Shares--Signature Guarantee";
                (3) any share certificates issued for any of the shares to be
                    redeemed (see "Certificated Shares" below); and
                (4) any additional documents which may be required by the
                    Transfer Agent for redemption by corporations,
                    partnerships or other organizations, executors,
                    administrators, trustees, custodians or guardians, or if
                    the redemption is requested by anyone other than the
                    shareholder(s) of record.
               Transfers of shares are subject to the same requirements. A
            signature guarantee is not required for redemptions of $50,000 or
            less, requested by and payable to all shareholders of record for
            the account, to be sent to the address of record for that account.
            To avoid delay in redemption or transfer, shareholders having any
            questions about these requirements should contact the Transfer
            Agent in writing or by calling 1-800-426-0107 before submitting a
            request. Redemption or transfer requests will not be honored until
            all required documents in the proper form have been received by
            the Transfer Agent. This redemption option does not apply to
            shares held in broker "street name" accounts.
               If the proceeds of the redemption (i) exceed $50,000, (ii) are
            to be paid to a person other than the record owner, (iii) are to
            be sent to an address other than the address of the account on the
            Transfer Agent's records, or (iv) are to be paid to a corporation,
            partnership, trust or fiduciary, the signature(s) on the redemp-
            tion request and on the certificates, if any, or stock power must
            be guaranteed as described above, except that the Distributor may
            waive the signature guarantee requirement for redemptions up to
            $2,500 by a trustee of a qualified retirement plan, the adminis-
            trator for which has an agreement with the Distributor.
 
 
TELEPHONE   The Trust accepts telephone requests for redemption of shares for
REDEMPTIONS amounts up to $50,000 within any 7 calendar day period, except for
            investors who have specifically declined telephone redemption
            privileges on the account application or elected in writing not to
            utilize telephone redemptions. The proceeds of a telephone redemp-
            tion will be sent to the record shareholder at his record address.
            Changes in account information must be made in a written authori-
            zation with a signature guarantee. See "How to Buy Shares--Signa-
            ture Guarantee". Telephone redemptions will not be accepted during
            the 30-day period following any change in an account's record ad-
            dress. This redemption option does not apply to shares held in
            broker "street name" accounts.
               By completing an account application, an investor agrees that
            the Trust, the Distributor and the Transfer Agent shall not be li-
            able for any loss incurred by the investor by reason of the Trust
            accepting unauthorized telephone redemption requests for his ac-
            count if the Trust reasonably believes the instructions to be gen-
            uine. Thus, shareholders risk possible losses in the event of a
            telephone redemption not authorized by them. The Trust may accept
            telephone redemption instructions from any person identifying him-
            self as the owner of an account or the owner's broker where the
            owner has not declined in writing to utilize this service. The
            Trust will employ reasonable procedures to confirm that instruc-
            tions
 
52
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            communicated by telephone are genuine, and may be liable for any
            losses due to unauthorized or fraudulent instructions if it fails
            to employ such procedures. The Trust will require a form of per-
            sonal identification prior to acting on a caller's telephone in-
            structions, will provide written confirmations of such transac-
            tions and will record telephone instructions.
               A shareholder making a telephone redemption should call the
            Transfer Agent at 1-800-426-0107 and state (i) the name of the
            shareholder as it appears on the Transfer Agent's records, (ii)
            his account number with the Trust, (iii) the amount to be with-
            drawn and (iv) the name of the person requesting the redemption.
            Usually the proceeds are sent to the investor on the next Trust
            business day after the redemption is effected, provided the re-
            demption request is received prior to the close of regular trading
            (normally 4:00 p.m., Eastern time) on the Exchange that day. If
            the redemption request is received after the close of the Ex-
            change, the redemption is effected on the following Trust business
            day at that day's net asset value and the proceeds are usually
            sent to the investor on the second following Trust business day.
            The Trust reserves the right to terminate or modify the telephone
            redemption service at any time. During times of severe disruptions
            in the securities markets, the volume of calls may make it diffi-
            cult to redeem by telephone, in which case a shareholder may wish
            to send a written request for redemption as described under "Writ-
            ten Requests" above. Telephone communications may be recorded by
            the Distributor or the Transfer Agent.
 
 
FUND LINK   If a shareholder has established Fund Link, the shareholder may
REDEMPTIONS redeem shares by telephone and have the redemption proceeds sent
            to a designated account at a financial institution. Fund Link is
            normally established within 45 days of receipt of a Fund Link ap-
            plication by the Transfer Agent. To use Fund Link for redemptions,
            call the Transfer Agent at 1-800-426-0107. Subject to the limita-
            tions set forth above under "Telephone Redemptions," the Distribu-
            tor, the Trust and the Transfer Agent may rely on instructions by
            any registered owner believed to be genuine and will not be re-
            sponsible to any shareholder for any loss, damage or expense aris-
            ing out of such instructions. Requests received by the Transfer
            Agent prior to the close of regular trading (normally 4:00 p.m.,
            Eastern time) on the Exchange on a business day will be processed
            at the net asset value on that day and the proceeds (less any
            CDSC) will normally be sent to the designated bank account on the
            following business day and received by the bank on the second or
            third business day. If the redemption request is received after
            the close of regular trading on the Exchange, the redemption is
            effected on the following business day. Shares purchased by check
            may not be redeemed through Fund Link until such shares have been
            owned (i.e., paid for) for at least 15 days. Fund Link may not be
            used to redeem shares held in certificated form. Changes in bank
            account information must be made by completing a new Fund Link ap-
            plication, signed by all owners of record of the account, with all
            signatures guaranteed. See "How to Buy Shares--Signature Guaran-
            tee." See "How to Buy Shares-- PIMCO Funds Fund Link" for informa-
            tion on establishing the Fund Link privilege. The Trust may termi-
            nate the Fund Link program at any time without notice to share-
            holders. This redemption option does not apply to shares held in
            broker "street name" accounts.
 
 
PIMCO FUNDS PIMCO Funds Automated Telephone System ("ATS") is an automated
AUTOMATED   telephone system that enables shareholders to perform a number of
TELEPHONE   account transactions automatically using a touch-tone telephone.
SYSTEM      ATS may be used on already-established Fund accounts after you ob-
            tain a Personal Identification Number (PIN) by calling the special
            ATS number: 1-800-223-2413.
            PURCHASING SHARES. You may purchase shares in amounts up to
            $100,000 by telephone by calling 1-800-223-2413. You must have es-
            tablished ATS privileges to link your bank account with the Fund
            to pay for these purchases.
            EXCHANGING SHARES. With the PIMCO Funds Exchange Privilege, you
            can exchange shares automatically by telephone from your Fund Link
            Account to another PIMCO Funds account you have already estab-
            lished by calling 1-800-223-2413. Please refer to "Exchange Privi-
            lege" below for details.
            REDEMPTIONS. You may redeem shares by telephone automatically by
            calling 1-800-223-2413 and the Fund will send the proceeds di-
            rectly to your Fund bank account. Please refer to "How to Redeem"
            below for details.
                                                                    Prospectus
                                                                              53
<PAGE>
 
            If a shareholder has given authorization for expedited wire re-
            demption, shares can be redeemed and the proceeds sent by federal
EXPEDITED   wire transfer to a single previously designated bank account. Re-
WIRE        quests received by the Trust prior to the close of the Exchange
TRANSFER    will result in shares being redeemed that day at the next deter-
REDEMPTIONS mined net asset value (less any CDSC)
            and normally the proceeds being sent to the designated bank ac-
            count the following business day. The bank must be a member of the
            Federal Reserve wire system. Delivery of the proceeds of a wire
            redemption request may be delayed by the Trust for up to 7 days if
            the Distributor deems it appropriate under then current market
            conditions. Once authorization is on file, the Trust will honor
            requests by any person identifying himself as the owner of an ac-
            count or the owner's broker by telephone at 1-800-426-0107 or by
            written instructions. The Trust cannot be responsible for the ef-
            ficiency of the Federal Reserve wire system or the shareholder's
            bank. The Trust does not currently charge for wire transfers. The
            shareholder is responsible for any charges imposed by the share-
            holder's bank. The minimum amount that may be wired is $2,500. The
            Trust reserves the right to change this minimum or to terminate
            the wire redemption privilege. Shares purchased by check may not
            be redeemed by wire transfer until such shares have been owned
            (i.e., paid for) for at least 15 days. Expedited wire transfer re-
            demptions may be authorized by completing a form available from
            the Distributor. Wire redemptions may not be used to redeem shares
            in certificated form. To change the name of the single bank ac-
            count designated to receive wire redemption proceeds, it is neces-
            sary to send a written request with signatures guaranteed to PIMCO
            Funds Distributors LLC, P.O. Box 9688, Providence, RI 02940-9688.
            See "How to Buy Shares-- Signature Guarantee." This redemption op-
            tion does not apply to shares held in broker "street name" ac-
            counts.
 
 
            To redeem shares for which certificates have been issued, the cer-
CERTIFICATEDtificates must be mailed to or deposited with the Trust, duly en-
SHARES      dorsed or accompanied by a duly endorsed stock power or by a writ-
            ten request for redemption. Signatures must be guaranteed as de-
            scribed under "How to Buy Shares--Signature Guarantee." Further
            documentation may be requested from institutions or fiduciary ac-
            counts, such as corporations, custodians (e.g., under the Uniform
            Gifts to Minors Act), executors, administrators, trustees or
            guardians ("institutional account owners"). The redemption request
            and stock power must be signed exactly as the account is regis-
            tered, including indication of any special capacity of the regis-
            tered owner.
 
 
AUTOMATIC   An investor who owns or buys shares of a Fund having a net asset
WITHDRAWAL  value of $10,000 or more may open an Automatic Withdrawal Plan and
PLAN        have a designated sum of money (not less than $100 per Fund) paid
            monthly (or quarterly) to the investor or another person. Such a
            plan may be established by completing the appropriate section of
            the Account Application or you may obtain an Automatic Withdrawal
            Plan Application from the Distributor or your broker. If an Auto-
            matic Withdrawal Plan is set up after the account is established
            providing for payment to a person other than the record share-
            holder or to an address other than the address of record, a signa-
            ture guarantee is required. See "How to Buy Shares--Signature
            Guarantee." Class A, Class B and Class C shares of any Fund are
            deposited in a plan account and all distributions are reinvested
            in additional shares of that class of the Fund at net asset value.
            Shares in a plan account are then redeemed at net asset value
            (less any applicable CDSC) to make each withdrawal payment. Any
            applicable CDSC may be waived for certain redemptions under an Au-
            tomatic Withdrawal Plan. See "Alternative Purchase Arrangements--
            Waiver of Contingent Deferred Sales Charges."
               Redemptions for the purpose of withdrawals are ordinarily made
            on the business day preceding the day of payment at that day's
            closing net asset value and checks are mailed on the day of pay-
            ment selected by the shareholder. The Transfer Agent may acceler-
            ate the redemption and check mailing date by one day to avoid
            weekend delays. Payment will be made to any person the investor
            designates; however, if the shares are registered in the name of a
            trustee or other fiduciary, payment will be made only to the fidu-
            ciary, except in the case of a profit-sharing or pension plan
            where payment will be made to the designee. As withdrawal payments
            may include a return of principal, they cannot be considered a
            guaranteed annuity or actual yield of income to the investor. The
            redemption of shares in connection with an Automatic Withdrawal
            Plan may result in a gain or loss for tax purposes. Continued
            withdrawals in excess of income
 
54
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            will reduce and possibly exhaust invested principal, especially in
            the event of a market decline. The maintenance of an Automatic
            Withdrawal Plan concurrently with purchases of additional shares
            of the Fund would be disadvantageous to the investor because of
            the CDSC that may become payable on such withdrawals in the case
            of Class A, Class B or Class C shares and because of the initial
            sales charge in the case of Class A shares. For this reason, the
            minimum investment accepted for a Fund while an Automatic With-
            drawal Plan is in effect for that Fund is $1,000, and an investor
            may not maintain a plan for the accumulation of shares of the Fund
            (other than through reinvestment of distributions) and an Auto-
            matic Withdrawal Plan at the same time. The Trust or the Distribu-
            tor may terminate or change the terms of the Automatic Withdrawal
            Plan at any time.
               Because the Automatic Withdrawal Plan may involve invasion of
            capital, investors should consider carefully with their own finan-
            cial advisers whether the plan and the specified amounts to be
            withdrawn are appropriate in their circumstances. The Trust and
            the Distributor make no recommendations or representations in this
            regard.
 
            Distributor and Distribution and Servicing Plans
 
            The Distributor, a wholly owned subsidiary of PIMCO Advisors L.P.,
            is the principal underwriter of the Trust's shares and in that
            connection makes distribution and servicing payments to partici-
            pating brokers and servicing payments to certain banks and other
            financial intermediaries in connection with the sale of Class B
            and Class C shares and servicing payments to participating bro-
            kers, certain banks and other financial intermediaries in connec-
            tion with the sale of Class A shares. In the case of Class A
            shares, these parties are also compensated based on the amount of
            the front-end sales charge reallowed by the Distributor, except in
            cases where Class A shares are sold without a front-end sales
            charge (although the Distributor may pay brokers additional com-
            pensation in connection with sales of Class A shares without a
            sales charge). In the case of Class B shares, participating bro-
            kers and other financial intermediaries are compensated by an ad-
            vance of a sales commission by the Distributor. In the case of
            Class C shares, part or all of the first year's distribution and
            servicing fee is generally paid at the time of sale. Pursuant to a
            Distribution Contract with the Trust, with respect to each Fund's
            Class A, Class B and Class C shares, the Distributor bears various
            other promotional and sales related expenses, including the cost
            of printing and mailing prospectuses to persons other than current
            shareholders. The Distributor, located at 2187 Atlantic Street,
            Stamford, Connecticut 06902, is a broker-dealer registered with
            the Securities and Exchange Commission.
 
            CLASS A SERVICING FEES As compensation for services rendered and
            expenses borne by the Distributor in connection with personal
            services rendered to Class A shareholders of the Trust and the
            maintenance of Class A shareholder accounts, the Trust pays the
            Distributor servicing fees up to the annual rates set forth below
            (calculated as a percentage of each Fund's average daily net as-
            sets attributable to Class A shares):
 
 
<TABLE>
<CAPTION>
                                  SERVICING
           FUND                   FEE
              -----------------------------
           <S>                    <C>
           All Funds except the
            Money Market Fund     .25%
              -----------------------------
           Money Market Fund*     .10%
</TABLE>
 
 
            *Subject to increase by action of the Trust's Trustees to a rate
            not exceeding .25% per annum. Also, subject to increase to a rate
            not exceeding .20% if the Distributor ceases to voluntarily waive
            any portion of the fee.
 
            CLASS B DISTRIBUTION AND SERVICING FEES As compensation for serv-
            ices rendered and expenses borne by the Distributor in connection
            with the distribution of Class B shares of the Trust and, in con-
            nection with personal services rendered to Class B shareholders of
            the Trust and the maintenance of Class B shareholder accounts, the
            Trust pays the Distributor servicing fees and distribution fees up
            to the annual rates set forth below (calculated as a percentage of
            each Fund's average daily net assets attributable to Class B
            shares):
                                                                    Prospectus
                                                                              55
<PAGE>
 
 
 
<TABLE>
<CAPTION>
                      SERVICING DISTRIBUTION
           FUND       FEE       FEE
              ------------------------------
           <S>        <C>       <C>
           All Funds  .25%      .75%
</TABLE>
 
            CLASS C DISTRIBUTION AND SERVICING FEES As compensation for serv-
            ices rendered and expenses borne by the Distributor in connection
            with the distribution of Class C shares of the Trust and, in con-
            nection with personal services rendered to Class C shareholders of
            the Trust and the maintenance of Class C shareholder accounts, the
            Trust pays the Distributor servicing fees and distribution fees up
            to the annual rates set forth below (calculated as a percentage of
            each Fund's average daily net assets attributable to Class C
            shares):
 
 
<TABLE>
<CAPTION>
                                        SERVICING DISTRIBUTION
           FUND                         FEE       FEE
              -------------------------------------------
           <S>                          <C>       <C>
           Total Return,
            High Yield,
            Long-Term U.S.
            Government,
            Global Bond
             II, Foreign Bond, Emerging
            Markets Bond
            and Strategic
            Balanced Funds              .25%      .75%
              -------------------------------------------
           Low Duration,
            Real Return
            Bond, Municipal
            Bond and
            StocksPLUS
            Funds*                      .25%      .50%
              -------------------------------------------
           Short-Term Fund*             .25%      .30%
              -------------------------------------------
           Money Market
            Fund*                       .10%      .00%
</TABLE>
 
            *Subject to increase by action of the Trust's Trustees to a rate
            not exceeding .75% per annum with respect to the distribution fee
            on shares of the Low Duration and Money Market Funds, and .25% per
            annum with respect to the servicing fee on shares of the Money
            Market Fund. With respect to the servicing fee on shares of the
            Money Market Fund, such fee is subject to increase to a rate of
            .20% if the Distributor ceases to voluntarily waive any portion of
            the fee. With respect to the distribution fee on shares of each of
            the Short-Term, Real Return Bond, Municipal Bond and StocksPLUS
            Funds, such fee is subject to an increase to a rate of .75% if the
            Distributor ceases to voluntarily waive any portion of the fee.
 
               The Class A servicing fees and Class B and Class C distribution
            and servicing fees paid to the Distributor are made under Distri-
            bution and Servicing Plans adopted pursuant to Rule 12b-l under
            the 1940 Act and are of the type known as "compensation" plans.
            This means that, although the Trustees of the Trust are expected
            to take into account the expenses of the Distributor and its pred-
            ecessors in their periodic review of the Distribution and Servic-
            ing Plans, the fees are payable to compensate the Distributor for
            services rendered even if the amount paid exceeds the Distribu-
            tor's expenses.
               The distribution fee applicable to Class B and Class C shares
            may be spent by the Distributor on any activities or expenses pri-
            marily intended to result in the sale of Class B or Class C
            shares, respectively, including compensation to, and expenses (in-
            cluding overhead and telephone expenses) of, financial consultants
            or other employees of the Distributor or of participating or in-
            troducing brokers who engage in distribution of Class B or Class C
            shares, printing of prospectuses and reports for other than exist-
            ing Class B or Class C shareholders, advertising, and preparation,
            printing and distribution of sales literature. The servicing fee,
            applicable to Class A, Class B and Class C shares of the Trust,
            may be spent by the Distributor on personal services rendered to
            shareholders of the Trust and the maintenance of shareholder ac-
            counts, including compensation to, and expenses (including tele-
            phone and overhead expenses) of, financial consultants or other
            employees of participating or introducing brokers, certain banks
            and other financial intermediaries who aid in the processing of
            purchase or redemption requests or the processing of dividend pay-
            ments, who provide information periodically to shareholders show-
            ing their positions in a Fund's shares, who forward communications
            from the Trust to shareholders, who render ongoing advice concern-
            ing the suitability of particular investment opportunities offered
            by the Trust in light of the shareholders' needs, who respond to
            inquiries from shareholders relating to such services, or who
            train personnel in the provision of such services. Distribution
            and servicing fees may also be spent on interest relating to
            unreimbursed distribution or servicing expenses from prior years.
 
56
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               Many of the Distributor's sales and servicing efforts involve
            the Trust as a whole, so that fees paid by Class A, Class B or
            Class C shares of any Fund may indirectly support sales and ser-
            vicing efforts relating to the other Funds' shares of the same
            class. In reporting its expenses to the Trustees, the Distributor
            itemizes expenses that relate to the distribution and/or servicing
            of a single Fund's shares, and allocates other expenses among the
            Funds based on their relative net assets. Expenses allocated to
            each Fund are further allocated among its classes of shares annu-
            ally based on the relative sales of each class, except for any ex-
            penses that relate only to the sale or servicing of a single
            class. The Distributor may make payments to brokers (and with re-
            spect to servicing fees only, to certain banks and other financial
            intermediaries) of up to the following percentages annually of the
            average daily net assets attributable to shares in the accounts of
            their customers or clients:
 
 
              CLASS A SHARES
 
<TABLE>
<CAPTION>
                                  SERVICING
                                  FEE(/1/)
              -----------------------------
           <S>                    <C>
           All Funds except the
            Money Market Fund     .25%
              -----------------------------
           Money Market Fund      .10%
</TABLE>
 
 
 
              CLASS B SHARES(/2/)
 
<TABLE>
<CAPTION>
                      SERVICING
                      FEE
              -----------------
           <S>        <C>
           All Funds  .25%
</TABLE>
 
 
 
              CLASS C SHARES--
              PURCHASED ON OR AFTER
              7/1/91(/3/)
 
<TABLE>
<CAPTION>
                            SERVICING DISTRIBUTION
                            FEE(/1/)  FEE(/1/)
              ------------------------------------
           <S>              <C>       <C>
           Total Return,
            High Yield,
            Long-Term U.S.
            Government,
            Global Bond II,
            Foreign Bond,
            Emerging
            Markets Bond
            and Strategic
            Balanced Funds  .25%      .65%
              ------------------------------------
           Low Duration,
            Real Return
            Bond, Municipal
            Bond and
            StocksPLUS
            Funds           .25%      .45%
              ------------------------------------
           Short-Term Fund  .25%      .25%
              ------------------------------------
           Money Market
            Fund            .10%      .00%
</TABLE>
 
 
 
              CLASS C SHARES--
              PURCHASED BEFORE 7/1/91
 
<TABLE>
<CAPTION>
                                  SERVICING
                                  FEE(/1/)
              -----------------------------
           <S>                    <C>
           All Funds except the
            Money Market Fund     .25%
              -----------------------------
           Money Market Fund      .10%
</TABLE>
 
            1. Applies, in part, to Class A, Class B and Class C shares of the
            Trust issued to former shareholders of PIMCO Advisors Funds in
            connection with the reorganizations/mergers of series of PIMCO Ad-
            visors Funds as/with Funds of the Trust in a transaction which
            took place on January 17, 1997.
            2. Payable only with respect to shares outstanding for one year or
            more.
            3. Payable only with respect to shares outstanding for one year or
            more except in the case of shares for which no payment is made to
            the party at the time of sale.
 
               The Distributor may from time to time pay additional cash bo-
            nuses or other incentives to selected participating brokers in
            connection with the sale or servicing of Class A, Class B and
            Class C shares of the Funds. On some occasions, such bonuses or
            incentives may be conditioned upon the sale of a specified minimum
            dollar amount of the shares of a
                                                                  Prospectus
                                                                              57
<PAGE>
 
            Fund and/or all of the Funds together or a particular class of
            shares, during a specific period of time. The Distributor cur-
            rently expects that such additional bonuses or incentives will not
            exceed .50% of the amount of any sale. Pacific Investment Manage-
            ment (in its capacity as administrator) may also pay participating
            brokers and other intermediaries for transfer agency and other
            services.
               If in any year the Distributor's expenses incurred in connec-
            tion with the distribution of Class B and Class C shares and, for
            Class A, Class B and Class C Shares, in connection with the ser-
            vicing of shareholders and the maintenance of shareholder ac-
            counts, exceed the distribution and/or servicing fees paid by the
            Trust, the Distributor would recover such excess only if the Dis-
            tribution and Servicing Plan with respect to such class of shares
            continues to be in effect in some later year when the distribution
            and/or servicing fees exceed the Distributor's expenses. The Trust
            is not obligated to repay any unreimbursed expenses that may exist
            at such time, if any, as the relevant Distribution and Servicing
            Plan terminates.
               From time to time, expenses of principal underwriters incurred
            in connection with the sale of shares of the Funds and in connec-
            tion with the servicing of shareholders of the Funds and the main-
            tenance of shareholder accounts may exceed the distribution and
            servicing fees collected by the Distributor. As of March 31, 1998,
            such expenses were approximately $2,927,000 in excess of payments
            under the Funds' Class A Distribution and Servicing Plan,
            $12,538,000 in excess of payments under the Funds' Class B Distri-
            bution and Servicing Plan, and $222,000 in excess of payments un-
            der the Funds' Class C Distribution and Servicing Plan.
 
            How Net Asset Value Is Determined
 
            The net asset values of Class A, Class B and Class C shares of
            each Fund will be determined once on each day on which the Ex-
            change is open as of the close of regular trading (normally 4:00
            p.m., Eastern time) on the Exchange. Net asset value will not be
            determined on days on which the Exchange is closed.
               The Money Market Fund's securities are normally valued using
            the amortized cost method of valuation. This involves valuing a
            security at cost on the date of acquisition and thereafter assum-
            ing a constant accretion of a discount or amortization of a pre-
            mium to maturity. See the Statement of Additional Information for
            a description of certain conditions and procedures followed by the
            Money Market Fund in connection with amortized cost valuation. For
            all other Funds, portfolio securities and other assets for which
            market quotations are readily available are stated at market val-
            ue. Market value is determined on the basis of last reported sales
            prices, or if no sales are reported, as is the case for most secu-
            rities traded over-the-counter, at the mean between representative
            bid and asked quotations obtained from a quotation reporting sys-
            tem or from established market makers. Fixed income securities,
            including those to be purchased under firm commitment agreements
            (other than obligations having a maturity of 60 days or less), are
            normally valued on the basis of quotations obtained from brokers
            and dealers or pricing services, which take into account appropri-
            ate factors such as institutional-sized trading in similar groups
            of securities, yield, quality, coupon rate, maturity, type of is-
            sue, trading characteristics, and other market data.
               Quotations of foreign securities in foreign currency are con-
            verted to U.S. dollar equivalents using foreign exchange quota-
            tions received from independent dealers. Short-term investments
            having a maturity of 60 days or less are valued at amortized cost,
            when the Board of Trustees determines that amortized cost is their
            fair value. Certain fixed income securities for which daily market
            quotations are not readily available may be valued, pursuant to
            guidelines established by the Board of Trustees, with reference to
            fixed income securities whose prices are more readily obtainable
            and whose durations are comparable to the securities being valued.
            Subject to the foregoing, other securities for which market quota-
            tions are not readily available are valued at fair value as deter-
            mined in good faith by the Board of Trustees.
               Each Fund's liabilities are allocated among its classes. The
            total of such liabilities allocated to a class plus that class's
            distribution and/or servicing fees and any other expenses spe-
            cially allocated to that class are then deducted from the class's
            proportionate interest in the Fund's assets, and the resulting
            amount for each class is divided by the number
 
58
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            of shares of that class outstanding to produce the class's "net
            asset value" per share. Under certain circumstances, the per share
            net asset value of the Class B and Class C shares of the Funds
            that do not declare regular income dividends on a daily basis may
            be lower than the per share net asset value of the Class A shares
            as a result of the daily expense accruals of the distribution fee
            applicable to the Class B and Class C shares. Generally, for Funds
            that pay income dividends, those dividends are expected to differ
            over time by approximately the amount of the expense accrual dif-
            ferential between a particular Fund's classes.
 
            Distributions
 
            Each Fund pays out as dividends substantially all of its net in-
            vestment income (which comes from dividends and interest it re-
            ceives or is deemed to receive from its investments) and net real-
            ized short-term capital gains. For these purposes and for federal
            income tax purposes, a portion of the premiums from certain ex-
            pired call or put options written by the Fund, net gains from
            closing purchase and sale transactions with respect to such op-
            tions, and net gains from futures transactions are treated as
            short-term capital gains. Each Fund distributes substantially all
            of its net realized capital gains, if any, after giving effect to
            any available capital loss carry-over.
               Shares begin earning dividends on the day after the date that
            funds are received by the Trust for the purchase of shares. For
            the Fixed Income Funds, dividends are declared daily from net in-
            vestment income to shareholders of record at the close of the pre-
            vious business day, and distributed to shareholders monthly. The
            Strategic Balanced and StocksPLUS Funds intend to declare and pay
            as a dividend substantially all of their net investment income on
            a quarterly basis. Any net realized capital gains from the sale of
            portfolio securities will be distributed no less frequently than
            once yearly.
               All dividends and/or distributions will be paid in the form of
            additional shares of the class of shares of the Fund to which the
            dividends and/or distributions relate or, at the election of the
            shareholder, of another Fund of the Trust or a series of PIMCO
            Funds: Multi-Manager Series as described below, at net asset val-
            ue, unless the shareholder elects to receive cash (either paid to
            shareholders directly or credited to their account with their par-
            ticipating broker). If a shareholder has elected to receive divi-
            dends and/or capital gain distributions in cash and the postal or
            other delivery service is unable to deliver checks to the share-
            holder's address of record, such shareholder's distributions will
            automatically be invested in the Money Market Fund until such
            shareholder is located. Dividends paid by each Fund with respect
            to each class of shares are calculated in the same manner and at
            the same time, but dividends on Class B and Class C shares are ex-
            pected to be lower than dividends on Class A shares as a result of
            the distribution fee applicable to Class B and Class C shares.
            There are no sales charges on reinvested dividends.
               Class A, Class B and Class C shareholders of the Trust may
            elect to invest dividends and/or distributions paid by any Fund in
            shares of the same class of any other Fund of the Trust or a se-
            ries of PIMCO Funds: Multi-Manager Series (including any PIMCO
            Funds Asset Allocation Series portfolio) which offers such class
            of shares at net asset value. The shareholder must have an account
            existing in the Fund selected for investment with the identical
            registered name and address and must elect this option on the ac-
            count application, on a form provided for that purpose or by a
            telephone request to the Transfer Agent at 1-800-426-0107. For
            further information on this option, contact your broker or call
            the Distributor at 1-800-426-0107.
 
                                                                    Prospectus
                                                                              59
<PAGE>
 
            Taxes
 
            Each Fund intends to qualify as a regulated investment company an-
            nually and to elect to be treated as a regulated investment com-
            pany under the Code. As such, a Fund generally will not pay fed-
            eral income tax on the income and gains it pays as dividends to
            its shareholders. In order to avoid a 4% federal excise tax, each
            Fund intends to distribute each year substantially all of its net
            income and gains.
               Shareholders subject to U.S. federal income tax will be subject
            to tax on dividends received from a Fund, regardless of whether
            received in cash or reinvested in additional shares. Distributions
            received by tax-exempt shareholders will not be subject to federal
            income tax to the extent permitted under applicable tax law. All
            shareholders must treat dividends, other than capital gain divi-
            dends or dividends that represent a return of capital to share-
            holders, as ordinary income.
               Dividends designated by a Fund as capital gain dividends de-
            rived from the Fund's net capital gain (that is, the excess of net
            long-term gain over net short-term loss) are taxable to sharehold-
            ers as long-term capital gain except as provided by an applicable
            tax exemption. Any distributions that are not from a Fund's net
            investment income, short-term capital gain, or net capital gain
            may be characterized as a return of capital to shareholders or, in
            some cases, as capital gain. Certain dividends declared in Octo-
            ber, November or December of a calendar year are taxable to share-
            holders (who are subject to tax on dividends) as though received
            on December 31 of that year if paid to shareholders during January
            of the following calendar year. Each Fund will advise shareholders
            annually of the amount and nature of the dividends paid to them.
               Dividends paid to shareholders by the Municipal Bond Fund which
            are derived from interest on Municipal Bonds are expected to be
            designated by the Fund as "exempt-interest dividends," and share-
            holders may generally exclude such dividends from gross income for
            federal income tax purposes. However, if a shareholder receives
            social security or railroad retirement benefits, the shareholder
            may be taxed on a portion of those benefits as a result of receiv-
            ing tax-exempt income. In addition, certain exempt-interest divi-
            dends could, as discussed below, cause certain shareholders to be-
            come subject to the alternative minimum tax and may increase the
            alternative minimum tax liability of shareholders already subject
            to this tax.
               To the extent that dividends paid to shareholders by the Munic-
            ipal Bond Fund are derived from taxable interest or from capital
            gains, such dividends will be subject to federal income tax. Any
            gain realized on a redemption of shares will be taxable gain, sub-
            ject to any applicable tax exemption for which an investor may
            qualify.
               Dividends derived from interest on certain U.S. Government se-
            curities may be exempt from state and local taxes, although inter-
            est on mortgage-backed U.S. Government securities (for example,
            interest on FNMA and GNMA Certificates) is generally not so ex-
            empt. The distributions of "exempt-interest dividends" paid by the
            Municipal Bond Fund may be exempt from state and local taxation
            when received by a shareholder to the extent that they are derived
            from interest on Municipal Bonds issued by the state or political
            subdivision in which such shareholder resides. The federal exemp-
            tion for "exempt-interest dividends" attributable to Municipal
            Bonds does not necessarily result in exemption of such dividends
            from income for the purpose of state and local taxes. The Trust
            will report annually on a state-by-state basis the source of in-
            come the Municipal Bond Fund receives on Municipal Bonds that was
            paid out as dividends during the preceding year.
               The Code also provides that exempt-interest dividends allocable
            to interest received from "private activity bonds" issued after
            August 7, 1986 are an item of tax preference for individual and
            corporate alternative minimum tax at the applicable rate for indi-
            viduals and corporations. Therefore, if the Municipal Bond Fund
            invests in such private activity bonds, certain of its sharehold-
            ers may become subject to the alternative minimum tax on that part
            of its distributions to them that are derived from interest income
            on such bonds, and certain shareholders already subject to such
            tax may have increased liability therefor. However, it is the
            present policy of the Municipal Bond Fund to invest no more than
            20% of its assets in such bonds. Other provisions of the Code af-
            fect the tax treatment of distributions from the Municipal Bond
            Fund for corporations, casualty insurance companies, and financial
            institutions. In particular, under the
 
60
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Code, for corporations, alternative minimum taxable income will be
            increased by a percentage of the amount by which the corporation's
            "adjusted current earnings" (which includes various items of tax
            exempt income) exceeds the amount otherwise determined to be al-
            ternative minimum taxable income. Accordingly, an investment in
            the Municipal Bond Fund may cause shareholders to be subject to
            (or result in an increased liability under) the alternative mini-
            mum tax.
               Dividends to shareholders of the Municipal Bond Fund derived
            from money market instruments and U.S. Government securities are
            generally taxable as ordinary income. The Fund may seek to reduce
            fluctuations in its net asset value by engaging in portfolio
            strategies involving options on securities, futures contracts, and
            options on futures contracts. Any gain derived by the Fund from
            the use of such instruments, including by reason of "marking to
            market," will be treated as a combination of short-term and long-
            term capital gain and, if not offset by realized capital losses
            incurred by the Fund, will be distributed to shareholders (possi-
            bly requiring the liquidation of other portfolio securities) and
            will be taxable to shareholders as a combination of ordinary in-
            come and long-term capital gain.
               Interest accrued by a Fund from inflation-indexed bonds will be
            includable in the Fund's gross income in the period in which it
            accrues. Periodic adjustments for inflation in the principal value
            of these securities also may give rise to original issue discount,
            which, likewise, will be includable in the Fund's gross income on
            a current basis, regardless of whether the Fund receives any cash
            payments. See "Taxation--Original Issue Discount" in the Statement
            of Additional Information. Amounts includable in a Fund's gross
            income become subject to tax-related distribution requirements.
            Accordingly, a Fund may be required to make annual distributions
            to shareholders in excess of the cash received in a given period
            from these investments. As a result, the Fund may be required to
            liquidate certain investments at a time when it is not advanta-
            geous to do so. If the principal value of an inflation-indexed
            bond is adjusted downward in any period as a result of deflation,
            the reduction may be treated as a loss to the extent the reduction
            exceeds coupon payments received in that period; in that case, the
            amount distributable by the Fund may be reduced and amounts dis-
            tributed previously in the taxable year may be characterized in
            some circumstances as a return of capital.
               Taxable shareholders should note that the timing of their in-
            vestment could have undesirable tax consequences. Dividends and
            distributions on a Fund's shares are generally subject to federal
            income tax as described herein to the extent they do not exceed
            the Fund's realized income and gains, even though such dividends
            and distributions may economically represent a return of a partic-
            ular shareholder's investment. Such distributions are likely to
            occur in respect of shares purchased at a time when the Fund's net
            asset value reflects gains that are either unrealized or realized
            but not distributed. Such realized gains may be required to be
            distributed even when a Fund's net asset value also reflects
            unrealized losses.
               The preceding discussion relates only to federal income tax;
            the consequences under other tax laws may differ. For additional
            information relating to the tax aspects of investing in a Fund,
            see the Statement of Additional Information.
 
            Management of the Trust
 
            The business affairs of the Trust are managed under the direction
            of the Board of Trustees. The Trustees are Guilford C. Babcock, R.
            Wesley Burns, Vern O. Curtis, Brent R. Harris, Thomas P. Kemp, and
            William J. Popejoy. Additional information about the Trustees and
            the Trust's executive officers may be found in the Statement of
            Additional Information under the heading "Management--Trustees and
            Officers."
 
 
INVESTMENT
ADVISER     Pacific Investment Management serves as investment adviser ("Ad-
            viser") to the Funds pursuant to an investment advisory contract.
            The Adviser is an investment management company founded in 1971,
            and had approximately $148 billion in assets under management as
            of September 30, 1998.
               Pacific Investment Management is a subsidiary of PIMCO Advisors
            L.P. ("PIMCO Advisors"). The general partners of PIMCO Advisors
            are PIMCO Partners, G.P. and PIMCO Advisors Holdings L.P. PIMCO
            Partners, G.P. is
                                                                    Prospectus
                                                                              61
<PAGE>
 
 
            a general partnership between PIMCO Holding LLC, a Delaware lim-
            ited liability company and an indirect wholly-owned subsidiary of
            Pacific Life Insurance Company, and PIMCO Partners LLC, a Califor-
            nia limited liability company controlled by the current Managing
            Directors and two former Managing Directors of Pacific Investment
            Management. PIMCO Partners, G.P. is the sole general partner of
            PIMCO Advisors Holdings L.P. Pacific Investment Management's ad-
            dress is 840 Newport Center Drive, Suite 300, Newport Beach, Cali-
            fornia 92660. Pacific Investment Management is registered as an
            investment adviser with the Securities and Exchange Commission and
            as a commodity trading advisor with the CFTC.
               The Adviser manages the investment and reinvestment of the as-
            sets of each Fund. The Adviser is responsible for placing orders
            for the purchase and sale of each Fund's investments directly with
            brokers or dealers selected by it in its discretion. See "Portfo-
            lio Transactions" in the Statement of Additional Information.
               Information about the individual portfolio managers responsible
            for management of the Trust's currently operational Funds offered
            in this Prospectus, including their occupations for the past five
            years, is provided below.
 
<TABLE>
<CAPTION>
                                          PORTFOLIO MANAGER AND BUSINESS
           FUND                           EXPERIENCE (PAST FIVE YEARS)
              -----------------------------------------------------------------
           <C>                            <S>
           MONEY MARKET FUND              Leslie Barbi, Senior Vice President,
                                          Pacific Investment Management. A
                                          Fixed Income Portfolio Manager, Ms.
                                          Barbi has managed the Money Market
                                          Fund since November 1, 1995. Prior to
                                          joining Pacific Investment Management
                                          in 1993, Ms. Barbi was associated
                                          with Salomon Brothers as a proprie-
                                          tary Portfolio Manager.
              -----------------------------------------------------------------
           SHORT-TERM FUND                William H. Gross, Managing Director,
           LOW DURATION FUND              Pacific Investment Management. A
           TOTAL RETURN FUND              Fixed Income Portfolio Manager, Mr.
           STRATEGIC BALANCED FUND        Gross is one of the founders of Pa-
           STOCKSPLUS FUND                cific Investment Management and has
                                          managed the Total Return and Low Du-
                                          ration Funds since their inception,
                                          May 11, 1987. Mr. Gross is the leader
                                          of the team which has managed the
                                          Short-Term, Strategic Balanced and
                                          StocksPLUS Funds since January 6,
                                          1998.
              -----------------------------------------------------------------
           REAL RETURN BOND FUND          John Brynjolfsson, Vice President,
                                          Pacific Investment Management. A
                                          Fixed Income Portfolio Manager, Mr.
                                          Brynjolfsson joined Pacific Invest-
                                          ment Management in 1989, and has man-
                                          aged the Real Return Bond Fund since
                                          its inception, January 29, 1997.
              -----------------------------------------------------------------
           HIGH YIELD FUND                Benjamin Trosky, Managing Director,
                                          Pacific Investment Management. A
                                          Fixed Income Portfolio Manager, Mr.
                                          Trosky joined Pacific Investment
                                          Management in 1990 and has managed
                                          the High Yield Fund since its incep-
                                          tion, December 16, 1992.
              -----------------------------------------------------------------
           MUNICIPAL BOND FUND            Benjamin Ehlert, Executive Vice Pres-
                                          ident, PIMCO. A Fixed Income Portfo-
                                          lio Manager, Mr. Ehlert has been as-
                                          sociated with PIMCO for over 23 years
                                          and has managed the PIMCO Municipal
                                          Bond Fund since its inception on De-
                                          cember 31, 1997.
              -----------------------------------------------------------------
           LONG-TERM U.S. GOVERNMENT FUND Pasi Hamalainen, Executive Vice Pres-
                                          ident, Pacific Investment Management.
                                          A Fixed Income Portfolio Manager, Mr.
                                          Hamalainen joined Pacific Investment
                                          Management in 1994 and has managed
                                          the Long-Term U.S. Government Fund
                                          since July 1, 1997.
              -----------------------------------------------------------------
           GLOBAL BOND FUND II            Lee R. Thomas, III, Managing Director
           FOREIGN BOND FUND              and Senior International Portfolio
                                          Manager, Pacific Investment Manage-
                                          ment. A Fixed Income Portfolio
                                          Manager, Mr. Thomas has managed the
                                          Foreign Bond Fund since July 13,
                                          1995, and the Global Bond Fund II
                                          since October 1, 1995. Prior to join-
                                          ing Pacific Investment Management in
                                          1995, Mr. Thomas was associated with
                                          Investcorp as a member of the manage-
                                          ment committee responsible for global
                                          securities and foreign exchange trad-
                                          ing. Prior to Investcorp, he was as-
                                          sociated with Goldman Sachs as an Ex-
                                          ecutive Director in foreign fixed in-
                                          come.
              -----------------------------------------------------------------
           EMERGING MARKETS BOND FUND     Michael J. Rosborough, Senior Vice
                                          President, Pacific Investment Manage-
                                          ment. A Fixed Income Portfolio Manag-
                                          er, Mr. Rosborough was associated
                                          with RBC Dominion in Tokyo as a Vice
                                          President and Manager in foreign
                                          fixed income prior to joining Pacific
                                          Investment Management in 1994.
</TABLE>
 
 
 
FUND
ADMINISTRATOR
            Pacific Investment Management also serves as administrator for the
            Funds' Class A, Class B and Class C shares pursuant to an adminis-
            tration agreement with the Trust. Pacific Investment Management
            provides administrative services for
 
62
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Class A, Class B and Class C shareholders of the Funds, which in-
            clude clerical help and accounting, bookkeeping, internal audit
            services, and certain other services required by the Funds, prepa-
            ration of reports to the Funds' shareholders and regulatory fil-
            ings. Pacific Investment Management may also retain certain of its
            affiliates to provide certain of these services. In addition, Pa-
            cific Investment Management, at its own expense, arranges for the
            provision of legal, audit, custody, transfer agency (including
            sub-transfer agency and other administrative services) and other
            services for the Funds, and is responsible for the costs of regis-
            tration of the Trust's shares and the printing of prospectuses and
            shareholder reports for current shareholders.
               The Funds (and not Pacific Investment Management) are responsi-
            ble for the following expenses: (i) salaries and other compensa-
            tion of any of the Trust's executive officers and employees who
            are not officers, directors, stockholders or employees of Pacific
            Investment Management or its subsidiaries or affiliates; (ii)
            taxes and governmental fees; (iii) brokerage fees and commissions
            and other portfolio transaction expenses; (iv) the costs of bor-
            rowing money, including interest expenses; (v) fees and expenses
            of the Trustees who are not "interested persons" of Pacific In-
            vestment Management or the Trust, and any counsel retained exclu-
            sively for their benefit; (vi) extraordinary expenses, including
            costs of litigation and indemnification expenses; (vii) expenses,
            such as organizational expenses, which are capitalized in accor-
            dance with generally accepted accounting principles; and (viii)
            any expenses allocated or allocable to a specific class of shares,
            which include distribution and servicing fees payable with respect
            to Class A, Class B and Class C shares, and may include certain
            other expenses as permitted by the Trust's Multi-Class Plan
            adopted pursuant to Rule 18f-3 under the 1940 Act, subject to re-
            view and approval by the Trustees.
 
 
            The Funds feature fixed advisory and administrative fee rates. For
            providing investment advisory and administrative services to the
            Funds as described above, Pacific Investment Management receives
            monthly fees from each Fund at an annual rate (i) based on the av-
            erage daily net assets of the Fund for advisory fees and, (ii) at-
            tributable in the aggregate to the Fund's Class A, Class B and
            Class C shares for administrative fees, as follows:
ADVISORY
AND
ADMINISTRATIVE
FEES
 
 
<TABLE>
<CAPTION>
                                                  ADVISORY
           FUND                                   FEE RATE
              --------------------------------------------------
           <S>                                    <C>
           Money Market Fund                      .15%
              --------------------------------------------------
           Strategic Balanced and StocksPLUS
            Funds                                 .40%
              --------------------------------------------------
           Emerging Markets Bond Fund             .45%
              --------------------------------------------------
           All other Funds                        .25%
 
 
 
<CAPTION>
                                                  ADMINISTRATIVE
           FUND                                   FEE RATE
              --------------------------------------------------
           <S>                                    <C>
           Money Market, Short-Term and Munici-
            pal Bond Funds                        .35%
              --------------------------------------------------
           Global Bond II and Foreign Bond Funds  .45%
              --------------------------------------------------
           Emerging Markets Bond Fund             .55%
              --------------------------------------------------
           All other Funds                        .40%
</TABLE>
 
 
               Both the investment advisory contract and administration agree-
            ment with respect to Class A, Class B and Class C shares of the
            Funds may be terminated by the Trustees at any time on 60 days'
            written notice. The investment advisory contract may be terminated
            by Pacific Investment Management on 60 days' written notice. Fol-
            lowing the expiration of the one-year period commencing with the
            effectiveness of the administration agreement, it may be
            terminated by Pacific Investment Management on 60 days' written
            notice. Following its initial two-year term, the investment advi-
            sory contract will continue from year to year if approved by the
            Trustees. Following its initial one-year term, the administration
            agreement with respect to Class A, Class B and Class C shares of
            the Funds will continue from year-to-year if approved by the
            Trustees.
                                                                    Prospectus
                                                                              63
<PAGE>
 
 
PORTFOLIO   Pursuant to the advisory contract, the Adviser places orders for
TRANSACTIONSthe purchase and sale of portfolio investments for the Funds' ac-
            counts with brokers or dealers selected by it in its discretion.
            In effecting purchases and sales of portfolio
            securities for the account of the Funds, the Adviser will seek the
            best price and execution of the Funds' orders. In doing so, a Fund
            may pay higher commission rates than the lowest available when the
            Adviser believes it is reasonable to do so in light of the value
            of the brokerage and research services provided by the broker ef-
            fecting the transaction.
               The Adviser manages the Funds without regard generally to re-
            strictions on portfolio turnover, except those imposed on its
            ability to engage in short-term trading by provisions of the fed-
            eral tax laws. The use of certain derivative instruments with rel-
            atively short maturities may tend to exaggerate the portfolio
            turnover rate for some of the Funds. Trading in fixed income secu-
            rities does not generally involve the payment of brokerage commis-
            sions, but does involve indirect transaction costs. The use of
            futures contracts may involve the payment of commissions to
            futures commission merchants. The higher the rate of portfolio
            turnover of a Fund, the higher all these transaction costs borne
            by the Fund generally will be. The portfolio turnover rate for
            each Fund for which financial highlights are provided in this Pro-
            spectus is set forth under "Financial Highlights."
               Some securities considered for investments by the Funds may
            also be appropriate for other clients served by the Adviser. If a
            purchase or sale of securities consistent with the investment pol-
            icies of a Fund and one or more of these clients served by the Ad-
            viser is considered at or about the same time, transactions in
            such securities will be allocated among the Fund and clients in a
            manner deemed fair and reasonable by the Adviser. The Adviser may
            aggregate orders for the Funds with simultaneous transactions en-
            tered into on behalf of other clients of the Adviser so long as
            price and transaction expenses are averaged either for that trans-
            action or for the day.
 
            Description of the Trust
 
 
CAPITALIZATION
            The Trust was organized as a Massachusetts business trust on Feb-
            ruary 19, 1987. The Board of Trustees may establish additional
            portfolios in the future. The capitalization of the Trust consists
            solely of an unlimited number of shares of beneficial interest
            with a par value of $0.0001 each. When issued, shares of the Trust
            are fully paid, non-assessable and freely transferable.
               Under Massachusetts law, shareholders could, under certain cir-
            cumstances, be held personally liable for the obligations of the
            Trust. However, the Declaration of Trust disclaims liability of
            the shareholders, Trustees or officers of the Trust for acts or
            obligations of the Trust, which are binding only on the assets and
            property of the Trust, and requires that notice of the disclaimer
            be given in each contract or obligation entered into or executed
            by the Trust or the Trustees. The Declaration of Trust also pro-
            vides for indemnification out of Trust property for all loss and
            expense of any shareholder held personally liable for the obliga-
            tions of the Trust. The risk of a shareholder incurring financial
            loss on account of shareholder liability is limited to circum-
            stances in which such disclaimer is inoperative or the Trust it-
            self is unable to meet its obligations, and thus should be consid-
            ered remote.
 
 
MULTIPLE    In addition to Class A, Class B and Class C shares, certain Funds
CLASSES OF  also offer Class D, Institutional Class and Administrative Class
SHARES      shares through separate prospectuses. See "Alternative Purchase
            Arrangements." These other classes of shares of the Funds may have
            different sales charges and expense levels, which will affect per-
            formance accordingly. This Prospectus relates only to the Class A,
            Class B and Class C shares of the Funds.
 
VOTING      Shareholders have the right to vote on the election of Trustees
            and on any and all matters on which the law or the Declaration of
            Trust states they may be entitled to vote. The Trust is not re-
            quired to hold regular annual meetings of Trust shareholders and
            does not intend to do so. Shareholders of a class of shares or
            Fund have separate voting rights with respect to matters that only
            affect that class or Fund. See "Other Information--Voting Rights"
            in the Statement of Additional Information.
 
64
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               The Declaration of Trust provides that the holders of not less
            than two-thirds of the outstanding shares of the Trust may remove
            a person serving as Trustee either by declaration in writing or at
            a meeting called for such purpose. The Trustees are required to
            call a meeting for the purpose of considering the removal of a
            person serving as Trustee if requested in writing to do so by the
            holders of not less than 10% of the outstanding shares of the
            Trust.
               Shares entitle their holders to one vote per share (with
            proportionate voting for fractional shares). As of September 3,
            1998, the following were shareholders of record of at least 25% of
            the outstanding voting securities of the indicated Fund: William
            Barron Hilton, Trustee (Beverly Hills, California) with respect to
            the Short-Term Fund; National Financial Services Corporation (New
            York, New York) with respect to the Real Return Bond Fund;
            Canterbury/Uniform Code Council (Pittsburgh, Pennsylvania) with
            respect to the Global Bond Fund II; Charles Schwab & Co., Inc.
            (San Francisco, California) with respect to the Foreign Bond Fund;
            Pacific Investment Management Company (Newport Beach, California)
            with respect to the Emerging Markets Bond Fund; and California
            Community Foundation (Los Angeles, California) with respect to the
            Strategic Balanced Fund. To the extent such shareholders are also
            the beneficial owners of those shares, they may be deemed to
            control (as that term is defined in the 1940 Act) the relevant
            Fund. As used in this Prospectus, the phrase "vote of a majority
            of the outstanding shares" of a Fund (or the Trust) means the vote
            of the lesser of: (1) 67% of the shares of the Fund (or the Trust)
            present at a meeting, if the holders of more than 50% of the
            outstanding shares are present in person or by proxy; or (2) more
            than 50% of the outstanding shares of the Fund (or the Trust).
 
            Mailings to Shareholders
 
            To reduce the volume of mail shareholders receive, it is antici-
            pated that only one copy of most Trust reports, such as the
            Trust's annual report, will be mailed to a shareholder's household
            (same surname, same address). A shareholder may call 1-800-227-
            7337 if additional shareholder reports are desired.
                                                                    Prospectus
                                                                              65
<PAGE>
 
            Appendix A
            Description of Duration
 
            Duration is a measure of the expected life of a fixed income secu-
            rity that was developed as a more precise alternative to the con-
            cept of "term to maturity." Traditionally, a fixed income
            security's "term to maturity" has been used as a proxy for the
            sensitivity of the security's price to changes in interest rates
            (which is the "interest rate risk" or "volatility" of the securi-
            ty). However, "term to maturity" measures only the time until a
            fixed income security provides its final payment, taking no ac-
            count of the pattern of the security's payments prior to maturity.
            In contrast, duration incorporates a bond's yield, coupon interest
            payments, final maturity and call features into one measure. Dura-
            tion management is one of the fundamental tools used by the Advis-
            er.
               Duration is a measure of the expected life of a fixed income
            security on a present value basis. Duration takes the length of
            the time intervals between the present time and the time that the
            interest and principal payments are scheduled or, in the case of a
            callable bond, expected to be received, and weights them by the
            present values of the cash to be received at each future point in
            time. For any fixed income security with interest payments occur-
            ring prior to the payment of principal, duration is always less
            than maturity. In general, all other things being equal, the lower
            the stated or coupon rate of interest of a fixed income security,
            the longer the duration of the security; conversely, the higher
            the stated or coupon rate of interest of a fixed income security,
            the shorter the duration of the security.
               Futures, options and options on futures have durations which,
            in general, are closely related to the duration of the securities
            which underlie them. Holding long futures or call option positions
            (backed by a segregated account of cash and cash equivalents) will
            lengthen a Fund's duration by approximately the same amount that
            holding an equivalent amount of the underlying securities would.
               Short futures or put option positions have durations roughly
            equal to the negative duration of the securities that underlie
            these positions, and have the effect of reducing portfolio dura-
            tion by approximately the same amount that selling an equivalent
            amount of the underlying securities would.
               There are some situations where even the standard duration cal-
            culation does not properly reflect the interest rate exposure of a
            security. For example, floating and variable rate securities often
            have final maturities of ten or more years; however, their inter-
            est rate exposure corresponds to the frequency of the coupon re-
            set. For inflation-indexed bonds, duration is calculated on the
            basis of modified real duration, which measures price changes of
            inflation-indexed bonds on the basis of changes in real, rather
            than nominal, interest rates. Another example where the interest
            rate exposure is not properly captured by duration is the case of
            mortgage pass-through securities. The stated final maturity of
            such securities is generally 30 years, but current prepayment
            rates are more critical in determining the securities' interest
            rate exposure. Finally, the duration of a fixed income security
            may vary over time in response to changes in interest rates and
            other market factors. In these and other similar situations, the
            Adviser will use more sophisticated analytical techniques that in-
            corporate the anticipated economic life of a security into the de-
            termination of its interest rate exposure.
 
66
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Appendix B
            Description of Securities Ratings
 
            Certain of the Funds make use of average portfolio credit quality
            standards to assist institutional investors whose own investment
            guidelines limit their investments accordingly. In determining a
            Fund's overall dollar-weighted average quality, unrated securities
            are treated as if rated, based on the Adviser's view of their com-
            parability to rated securities. A Fund's use of average quality
            criteria is intended to be a guide for those institutional invest-
            ors whose investment guidelines require that assets be invested
            according to comparable criteria. Reference to an overall average
            quality rating for a Fund does not mean that all securities held
            by the Fund will be rated in that category or higher. A Fund's in-
            vestments may range in quality from securities rated in the lowest
            category in which the Fund is permitted to invest to securities
            rated in the highest category (as rated by Moody's or S&P or, if
            unrated, determined by the Adviser to be of comparable quality).
            The percentage of a Fund's assets invested in securities in a par-
            ticular rating category will vary. Following is a description of
            Moody's and S&P's ratings applicable to fixed income securities.
 
 
MOODY'S     CORPORATE AND MUNICIPAL BOND RATINGS
INVESTORS      Aaa: Bonds which are rated Aaa are judged to be of the best
SERVICE,    quality. They carry the smallest degree of investment risk and are
INC.        generally referred to as "gilt edge." Interest payments are pro-
            tected by a large or by an exceptionally stable margin and princi-
            pal is secure. While the various protective elements are likely to
            change, such changes as can be visualized are most unlikely to im-
            pair the fundamentally strong position of such issues.
               Aa: Bonds which are rated Aa are judged to be of high quality
            by all standards. Together with the Aaa group they comprise what
            are generally known as high-grade bonds. They are rated lower than
            the best bonds because margins of protection may not be as large
            as in Aaa securities or fluctuation of protective elements may be
            of greater amplitude or there may be other elements present that
            make the long-term risks appear somewhat larger than with Aaa se-
            curities.
               A: Bonds which are rated A possess many favorable investment
            attributes and are to be considered as upper-medium-grade obliga-
            tions. Factors giving security to principal and interest are con-
            sidered adequate but elements may be present that suggest a sus-
            ceptibility to impairment sometime in the future.
               Baa: Bonds which are rated Baa are considered as medium-grade
            obligations (i.e., they are neither highly protected nor poorly
            secured). Interest payments and principal security appear adequate
            for the present but certain protective elements may be lacking or
            may be characteristically unreliable over any great length of
            time. Such bonds lack outstanding investment characteristics and
            in fact have speculative characteristics as well.
               Ba: Bonds which are rated Ba are judged to have speculative el-
            ements; their future cannot be considered as well-assured. Often
            the protection of interest and principal payments may be very mod-
            erate and thereby not well safeguarded during both good and bad
            times over the future. Uncertainty of position characterizes bonds
            in this class.
               B: Bonds which are rated B generally lack characteristics of a
            desirable investment. Assurance of interest and principal payments
            or of maintenance of other terms of the contract over any long pe-
            riod of time may be small.
               Caa: Bonds which are rated Caa are of poor standing. Such is-
            sues may be in default or there may be present elements of danger
            with respect to principal or interest.
               Ca: Bonds which are rated Ca represent obligations which are
            speculative in a high degree. Such issues are often in default or
            have other marked shortcomings.
               C: Bonds which are rated C are the lowest rated class of bonds
            and issues so rated can be regarded as having extremely poor pros-
            pects of ever attaining any real investment standing.
               Moody's applies numerical modifiers, 1, 2, and 3 in each ge-
            neric rating classified from Aa through B in its corporate bond
            rating system. The modifier 1 indicates that the security ranks in
            the higher end of its generic rating category; the modifier 2 in-
            dicates a mid-range ranking; and the modifier 3 indicates that the
            issue ranks in the lower end of its generic rating category.
 
                                                                             67
                                                                    Prospectus
<PAGE>
 
 
            CORPORATE SHORT-TERM DEBT RATINGS
            Moody's short-term debt ratings are opinions of the ability of is-
            suers to repay punctually senior debt obligations which have an
            original maturity not exceeding one year. Obligations relying upon
            support mechanisms such as letters of credit and bonds of indem-
            nity are excluded unless explicitly rated.
               Moody's employs the following three designations, all judged to
            be investment grade, to indicate the relative repayment ability of
            rated issuers:
               PRIME-1: Issuers rated Prime-1 (or supporting institutions)
            have a superior ability for repayment of senior short-term debt
            obligations. Prime-1 repayment ability will often be evidenced by
            many of the following characteristics: leading market positions in
            well-established industries; high rates of return on funds em-
            ployed; conservative capitalization structure with moderate reli-
            ance on debt and ample asset protection; broad margins in earnings
            coverage of fixed financial charges and high internal cash genera-
            tion; and well-established access to a range of financial markets
            and assured sources of alternate liquidity.
               PRIME-2: Issuers rated Prime-2 (or supporting institutions)
            have a strong ability for repayment of senior short-term debt ob-
            ligations. This will normally be evidenced by many of the charac-
            teristics cited above but to a lesser degree. Earnings trends and
            coverage ratios, while sound, may be more subject to variation.
            Capitalization characteristics, while still appropriate, may be
            more affected by external conditions. Ample alternate liquidity is
            maintained.
               PRIME-3: Issuers rated Prime-3 (or supporting institutions)
            have an acceptable ability for repayment of senior short-term ob-
            ligations. The effect of industry characteristics and market com-
            positions may be more pronounced. Variability in earnings and
            profitability may result in changes in the level of debt protec-
            tion measurements and may require relatively high financial lever-
            age. Adequate alternate liquidity is maintained.
               NOT PRIME: Issuers rated Not Prime do not fall within any of
            the Prime rating categories.
 
 
STANDARD &  CORPORATE AND MUNICIPAL BOND RATINGS
POOR'S
RATINGS     INVESTMENT GRADE
SERVICES       AAA: Debt rated AAA has the highest rating assigned by S&P. Ca-
            pacity to pay interest and repay principal is extremely strong.
               AA: Debt rated AA has a very strong capacity to pay interest
            and repay principal and differs from the highest rated issues only
            in small degree.
               A: Debt rated A has a strong capacity to pay interest and repay
            principal although it is somewhat more susceptible to the adverse
            effects of changes in circumstances and economic conditions than
            debt in higher rated categories.
               BBB: Debt rated BBB is regarded as having an adequate capacity
            to pay interest and repay principal. Whereas it normally exhibits
            adequate protection parameters, adverse economic conditions, or
            changing circumstances are more likely to lead to a weakened ca-
            pacity to pay interest and repay principal for debt in this cate-
            gory than in higher-rated categories.
 
            SPECULATIVE GRADE
            Debt rated BB, B, CCC, CC, and C is regarded as having predomi-
            nantly speculative characteristics with respect to capacity to pay
            interest and repay principal. BB indicates the least degree of
            speculation and C the highest. While such debt will likely have
            some quality and protective characteristics, these are outweighed
            by large uncertainties or major exposures to adverse conditions.
               BB: Debt rated BB has less near-term vulnerability to default
            than other speculative issues. However, it faces major ongoing un-
            certainties or exposure to adverse business, financial, or eco-
            nomic conditions which could lead to inadequate capacity to meet
            timely interest and principal payments. The BB rating category is
            also used for debt subordinated to senior debt that is assigned an
            actual or implied BBB- rating.
 
68
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               B: Debt rated B has a greater vulnerability to default but cur-
            rently has the capacity to meet interest payments and principal
            repayments. Adverse business, financial, or economic conditions
            will likely impair capacity or willingness to pay interest and re-
            pay principal. The B rating category is also used for debt subor-
            dinated to senior debt that is assigned an actual or implied BB or
            BB- rating.
               CCC: Debt rated CCC has a currently identifiable vulnerability
            to default and is dependent upon favorable business, financial,
            and economic conditions to meet timely payment of interest and re-
            payment of principal. In the event of adverse business, financial
            or economic conditions, it is not likely to have the capacity to
            pay interest and repay principal. The CCC rating category is also
            used for debt subordinated to senior debt that is assigned an ac-
            tual or implied B or B- rating.
               CC: The rating CC is typically applied to debt subordinated to
            senior debt that is assigned an actual or implied CCC rating.
               C: The rating C is typically applied to debt subordinated to
            senior debt that is assigned an actual or implied CCC- debt rat-
            ing. The C rating may be used to cover a situation where a bank-
            ruptcy petition has been filed, but debt service payments are con-
            tinued.
               CI: The rating CI is reserved for income bonds on which no in-
            terest is being paid.
               D: Debt rated D is in payment default. The D rating category is
            used when interest payments or principal payments are not made on
            the date due even if the applicable grace period has not expired,
            unless S&P believes that such payments will be made during such
            grace period. The D rating will also be used upon the filing of a
            bankruptcy petition if debt service payments are jeopardized.
               Plus (+) or Minus (-): The ratings from AA to CCC may be modi-
            fied by the addition of a plus or minus sign to show relative
            standing within the major rating categories.
               Provisional ratings: The letter "p" indicates that the rating
            is provisional. A provisional rating assumes the successful com-
            pletion of the project being financed by the debt being rated and
            indicates that payment of debt service requirements is largely or
            entirely dependent upon the successful and timely completion of
            the project. This rating, however, while addressing credit quality
            subsequent to completion of the project, makes no comment on the
            likelihood of, or the risk of default upon failure of, such com-
            pletion. The investor should exercise his own judgment with re-
            spect to such likelihood and risk.
               r: The "r" is attached to highlight derivative, hybrid, and
            certain other obligations that S&P believes may experience high
            volatility or high variability in expected returns due to non-
            credit risks. Examples of such obligations are: securities whose
            principal or interest return is indexed to equities, commodities,
            or currencies; certain swaps and options; and interest only and
            principal only mortgage securities.
               The absence of an "r" symbol should not be taken as an indica-
            tion that an obligation will exhibit no volatility or variability
            in total return.
               N.R.: Not rated.
               Debt obligations of issuers outside the United States and its
            territories are rated on the same basis as domestic corporate and
            municipal issues. The ratings measure the creditworthiness of the
            obligor but do not take into account currency exchange and related
            uncertainties.
 
            COMMERCIAL PAPER RATING DEFINITIONS
            An S&P commercial paper rating is a current assessment of the
            likelihood of timely payment of debt having an original maturity
            of no more than 365 days. Ratings are graded into several catego-
            ries, ranging from A for the highest quality obligations to D for
            the lowest. These categories are as follows:
               A-1: This highest category indicates that the degree of safety
            regarding timely payment is strong. Those issues determined to
            possess extremely strong safety characteristics are denoted with a
            plus sign (+) designation.
               A-2: Capacity for timely payment on issues with this designa-
            tion is satisfactory. However, the relative degree of safety is
            not as high as for issues designated A-1.
 
                                                                             69
                                                                    Prospectus
<PAGE>
 
               A-3: Issues carrying this designation have adequate capacity
            for timely payment. They are, however, more vulnerable to the ad-
            verse effects of changes in circumstances than obligations carry-
            ing the higher designations.
               B: Issues rated B are regarded as having only speculative ca-
            pacity for timely payment.
               C: This rating is assigned to short-term debt obligations with
            a doubtful capacity for payment.
               D: Debt rated D is in payment default. The D rating category is
            used when interest payments or principal payments are not made on
            the date due, even if the applicable grace period has not expired,
            unless S&P believes that such payments will be made during such
            grace period.
               A commercial paper rating is not a recommendation to purchase,
            sell or hold a security inasmuch as it does not comment as to mar-
            ket price or suitability for a particular investor. The ratings
            are based on current information furnished to S&P by the issuer or
            obtained from other sources it considers reliable. S&P does not
            perform an audit in connection with any rating and may, on occa-
            sion, rely on unaudited financial information. The ratings may be
            changed, suspended, or withdrawn as a result of changes in or un-
            availability of such information.
 
70
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
<TABLE> 
<CAPTION> 
<C>                 <S> 
                    ------------------------------------------------------------------------------------------
PIMCO Funds:        INVESTMENT ADVISOR AND ADMINISTRATOR
Pacific Investment   
Management Series   Pacific Investment Management Company, 840 Newport Center Drive, Suite 300,
                    Newport Beach, CA 92660
                    ------------------------------------------------------------------------------------------
                    DISTRIBUTOR

                    PIMCO Funds Distributors LLC, 2187 Atlantic Street, Stamford CT 06902
                    ------------------------------------------------------------------------------------------
                    CUSTODIAN

                    Investors Fiduciary Trust Company, 801 Pennsylvania, Kansas City, MO 64105
                    ------------------------------------------------------------------------------------------
                    SHAREHOLDER SERVICING AGENT AND TRANSFER AGENT

                    First Data Investor Services Group, Inc., P.O. Box 9688, Providence, RI 02940-9688
                    ------------------------------------------------------------------------------------------
                    INDEPENDENT ACCOUNTANTS

                    PricewaterhouseCoopers LLP, 1055 Broadway, Kansas City, MO 64105
                    ------------------------------------------------------------------------------------------
                    LEGAL COUNSEL

                    Dechert Price & Rhoads, 1775 Eye Street N.W., Washington, D.C. 20006
                    ------------------------------------------------------------------------------------------
                    For further information about the PIMCO Funds, call 1-800-426-0107 or visit our Web site  
                    at www.pimcofunds.com.
</TABLE> 
<PAGE>
 
                           PIMCO FUNDS IS ON THE WEB
                              www.pimcofunds.com

<TABLE> 
<C>                     <C>                           <C>                        <S> 
A Partial List of       PIMCO Funds Distributors LLC                   
What's Available:       is pleased to announce   
                        the launch of its Web          
Daily Manager           site. You and your            
Commentary              financial advisor now            [PICTURE]                  [PICTURE]
                        have around-the-clock         
Fund Manager Bios       access to the most            
                        timely and comprehensive      
Current and             information available         
Historical Fund         on all of the PIMCO           
Performance             Funds. In addition, the       INVESTMENT INSIGHT         RESOURCES
                        site includes daily           The Investment             Our Resources section features a variety 
Lipper Rankings         commentary from our fund      Insight section            of useful information, including: 
                        managers, with insights       provides an overview       
Morningstar Ratings     on the economy and other      of six investment          *an on-line document library with
                        factors affecting the         management firms           applications and forms that you can view          
Listing of Fund         stock and bond markets.       under the PIMCO            and print                                          
Portfolio Holdings                                    Advisors L.P. umbrella.                                                       
                                                      You'll find an             *a literature-by-mail "catalog", so you           
Risk Analysis                                         explanation of each        can order free materials                          
                                                      firm's investment                                                            
Daily Share Prices            [PICTURE]               process, biographies       *information about our convenient shareholder     
                                                      of the investment          services, such as Auto-Invest, Fund Link and      
Downloadable                                          team, manager updates      our 24-Hour Telephone Information System           
Literature Section                                    and more.                  
                                                                                 *a listing of the features and 
On-Line Literature      You'll find the site to                                  benefits of the retirement plans           
Requests                be informative and                                       offered by PIMCO Funds.        
                        easy-to-use. It's                                                                                     
Resources for           divided into three main           [PICTURE]              *a feature--"My Portfolio"-- which                
Investment              sections: Investment                                     enables you to track your portfolio               
Professionals           Insight, Fund                                            (including PIMCO Funds, other funds,              
                        Information and                                          stocks, futures and options), get         
                        Resources. And there                                     detailed stock quotes and more.           
                        are several functions         FUND INFORMATION                                                     
                        that can help you             In the Fund                QUESTIONS?                                
                        navigate your way             Information section        We're sure you'll find the                 
                        around the site. We can       you'll access detailed     PIMCO Funds Web site to be                 
                        be found on the               profiles of all the        an invaluable tool. If you                 
                        Worldwide Web at              PIMCO Funds, including     have any comments or questions                    
                        www.pimcofunds.com.           current and historical     about the site, please call us                     
                                                      performance, Lipper        today at 1-800-426-0107. Or, use                 
                                                      rankings and Morningstar   the e-mail feature of the site to         
                                                      ratings. Additionally,     contact us.                                       
                                                      we provide a summary of                                               
                                                      a fund's portfolio--        
                                                      complete with risk         
                                                      analysis data. You can     
                                                      also obtain daily fund 
                                                      share prices. Please 
                                                      read the relevant
                                                      prospectus carefully
                                                      before you invest
                                                      in any PIMCO Fund.

</TABLE> 
                                                                       P I M C O
                                                                       ---------
                                                                           FUNDS


<PAGE>
 
                            PIMCO TOTAL RETURN FUND

- --------------------------------------------------------------------------------
OBJECTIVE

Seeking maximum total return, consistent with preservation of capital and 
prudent investment management.

- --------------------------------------------------------------------------------
PRIMARY INVESTMENTS

An intermediate-term portfolio of investment grade fixed income securities.

- --------------------------------------------------------------------------------
INVESTMENT STYLE

TOTAL RETURN STRATEGY  The Fund seeks total return -- yield plus appreciation.

RISK MANAGEMENT  The portfolio manager seeks to manage risk in a number of ways,
such as maintaining an intermediate-term portfolio with a duration that normally
varies within a 3- to 6-year time frame. However, net asset value will
fluctuate.

QUALITY  The Fund maintains a portfolio primarily consisting of investment 
grade fixed income securities.

DIVERSIFICATION  Subject to market conditions, the fund actively invests across 
all sectors of the fixed income market in order to maximize investment 
opportunities.

- --------------------------------------------------------------------------------
PORTFOLIO MANAGER

Bill Gross of Pacific Investment Management Company, a PIMCO Advisors 
institutional investment firm. With approximately $148 billion in assets under 
management, the firm is one of the largest bond managers in the country. Bill
Gross has over 27 years investment experience.

- --------------------------------------------------------------------------------
FUND PERFORMANCE 

For the latest PIMCO Total Return Fund performance, call 1-800-227-7337 or visit
our Web site at www.pimcofunds.com.

For more information about the Fund, see the following prospectus.
PIMCO Funds Distributors LLC, 2187 Atlantic Street, Stamford, CT 06902,
www.pimcofunds.com.

                                                                       P I M C O
                                                                           FUNDS
<PAGE>
 
            Prospectus
            PIMCO Total Return Fund
            December 11, 1998
 
            PIMCO Funds (the "Trust") is an open-end series management invest-
            ment company consisting of twenty-five separate investment portfo-
            lios, each with different investment objectives and strategies.
            The Total Return Fund (the "Fund") is described herein. The Trust
            is designed to provide access to the professional investment man-
            agement services offered by Pacific Investment Management Company
            ("Pacific Investment Management"), which serves as investment ad-
            viser (the "Adviser") to the Fund. The address of PIMCO Funds is
            840 Newport Center Drive, Suite 300, Newport Beach, CA 92660.
 
            The Fund offers Class A shares in this Prospectus, which is in-
            tended for participants in designated employer-sponsored retire-
            ment or savings plans. Through other prospectuses, the Fund and
            the other series of the Trust offer Class A shares (sold subject
            to a front-end sales charge) for public investment, and offer up
            to five additional classes of shares, including Institutional
            Class shares, Administrative Class shares, Class B shares (sold
            subject to a contingent deferred sales charge), Class C shares
            (sold subject to an asset based sales charge) and Class D Shares.
            See "Description of the Trust--Multiple Classes of Shares."
 
            This Prospectus concisely describes the information investors
            should know before investing in the Fund. Please read this Pro-
            spectus carefully and keep it for further reference. Information
            about the investment objective of the Fund, along with a detailed
            description of the types of securities in which the Fund may in-
            vest and of investment policies and restrictions applicable to the
            Fund, are set forth in this Prospectus. There can be no assurance
            that the investment objective of the Fund will be achieved. Be-
            cause the market value of the Fund's investments will change, the
            investment returns and net asset value per share of the Fund will
            vary.
 
            The Fund is an investment option under an employer-sponsored re-
            tirement or savings program. The administrator of a retirement
            plan or an employee benefits office can provide participants with
            detailed information on how to participate in such a plan and how
            to elect the Fund as an investment option. Please call 800-426-
            0107 with any questions about the Fund. Questions about a partici-
            pant's plan account should be directed to the plan administrator
            or the organization that provides recordkeeping services for the
            plan.
 
            A Statement of Additional Information, dated November 25, 1998, as
            amended or supplemented from time to time, is available free of
            charge by writing to PIMCO Funds Distributors LLC (the "Distribu-
            tor"), 2187 Atlantic Street, Stamford, Connecticut 06902, or by
            telephoning 800-426-0107. The Statement of Additional Information,
            which contains more detailed information about the Trust, has been
            filed with the Securities and Exchange Commission and is incorpo-
            rated by reference in this Prospectus. The Securities and Exchange
            Commission maintains an Internet World Wide Web site (at
            www.sec.gov) which contains the Statement of Additional Informa-
            tion, materials that are incorporated by reference in this Pro-
            spectus and the Statement of Additional Information, and other in-
            formation about the Fund.
 
            THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SE-
            CURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMIS-
            SION, 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 OF-
            FENSE.
 
            SHARES OF THE FUND ARE NOT DEPOSITS OR OBLIGATIONS OF, OR GUARAN-
            TEED OR ENDORSED BY, ANY FINANCIAL INSTITUTION, AND THE SHARES ARE
            NOT FEDERALLY INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORA-
            TION, THE FEDERAL RESERVE BOARD OR ANY OTHER AGENCY.
 
            THE FUND MAY INVEST ALL OF ITS ASSETS IN DERIVATIVE INSTRUMENTS,
            SOME OF WHICH MAY BE PARTICULARLY SENSITIVE TO CHANGES IN PREVAIL-
            ING INTEREST RATES. UNEXPECTED CHANGES IN INTEREST RATES MAY AD-
            VERSELY AFFECT THE VALUE OF THE FUND'S INVESTMENTS IN PARTICULAR
            DERIVATIVE INSTRUMENTS.
 

 
<TABLE>
<CAPTION> 
TABLE OF CONTENTS
<S>                                 <C>  <C>                                 <C>
Overview..........................   3   How to Redeem.....................  23
Schedule of Fees..................   3   Distributor and Distribution and      
Financial Highlights..............   4   Servicing Plan....................  23
Investment Objective and                 How Net Asset Value Is Determined.  24
Policies..........................   5   Distributions.....................  25
Investment Risks and                     Taxes.............................  25
Considerations....................   6   Management of the Trust...........  26
Characteristics and Risks of             Description of the Trust..........  28
 Securities and Investment               Mailings to Shareholders..........  29
 Techniques.......................   7   Appendix A -- Description of          
Performance Information...........  21   Duration..........................  30
How to Buy Shares.................  22   Appendix B -- Description of          
Exchange Privilege................  23   Securities Ratings................  31 
</TABLE>
 PIMCO Funds: Pacific Investment Management Series
2
<PAGE>
 
            Overview

            Pacific Investment Management, a subsidiary partnership of PIMCO
            Advisors L.P., is the investment adviser of the Fund. Pacific In-
            vestment Management is one of the premier fixed income investment
            management firms in the U.S. As of September 30, 1998, Pacific In-
            vestment Management had over $148 billion in assets under manage-
            ment. Pacific Investment Management invests in all sectors of the
            fixed income market, using its total return philosophy--seeking
            capital appreciation as well as yield.
 
 
FUND
PROFILE  
<TABLE>
<CAPTION>
           PIMCO FUND NAME   PRIMARY OBJECTIVE                 DURATION  CREDIT QUALITY/(1)/
           ---------------------------------------------------------------------------------
           <S>               <C>                               <C>       <C>
           TOTAL RETURN
            FUND             Maximum total return, consistent  3-6 years B to Aaa; max
                             with preservation of capital                10% below Baa
                             and prudent investment management
         </TABLE>
 
            1. As rated by Moody's Investors Service, Inc., or if unrated, de-
            termined to be of comparable quality. For specific information
            concerning the credit quality of the securities in the Fund's
            portfolio, see "Investment Objective and Policies."
 
            Schedule of Fees
 
 
SHAREHOLDER
TRANSACTION
EXPENSES
 
<TABLE>
<CAPTION>
                                                           CLASS A SHARES
           --------------------------------------------------------------
           <S>                                             <C>
           MAXIMUM INITIAL SALES CHARGE IMPOSED ON
            PURCHASES                                         None/(1)/
           --------------------------------------------------------------
           MAXIMUM SALES CHARGE IMPOSED ON REINVESTED
            DIVIDENDS                                         None
           --------------------------------------------------------------
           MAXIMUM CONTINGENT DEFERRED SALES CHARGE
            ("CDSC")                                          None/(1)/
           --------------------------------------------------------------
           EXCHANGE FEE                                       None
</TABLE>
 
            1. Applies only to shares purchased through designated 401(k)
            plans.
 
 
OPERATING
EXPENSES 
<TABLE>
<CAPTION>
                                                                 EXAMPLE: You
                                                                 would pay the
                                                                 following
                                                                 expenses on a
                                                                 $1,000 investment
                                                                 assuming (1) 5%
                                                                 annual return and
                                                                 (2) redemption at
                    ANNUAL FUND OPERATING EXPENSES               the end of each
                    (As a percentage of average net assets):     time period:

                                                      TOTAL FUND
                    ADVISORY ADMINISTRATIVE 12b-1     OPERATING  YEAR
           FUND     FEE      FEE            FEES/(1)/ EXPENSES   1    3   5   10
           -----------------------------------------------------------------------
           <S>      <C>      <C>            <C>       <C>        <C>  <C> <C> <C>
           TOTAL
            RETURN  .25%     .40%           .25%      .90%       $9   $29 $50 $111
           -----------------------------------------------------------------------
         </TABLE>
 
            1. 12b-1 fees represent servicing fees which are paid annually to
            the Distributor and repaid to participating brokers, certain banks
            and other financial intermediaries. See "Distributor and Distribu-
            tion and Servicing Plans."
 
            The purpose of the foregoing tables is to assist investors in un-
            derstanding the various costs and expenses of the Trust that are
            borne directly or indirectly by Class A shareholders of the Fund.
            The information has been restated to reflect the Fund's current
            fees and expenses.
 
            NOTE: THE FIGURES SHOWN IN THE EXAMPLE ARE ENTIRELY HYPOTHETICAL,
            AND ASSUME NO PAYMENT OF A SALES LOAD. THEY ARE NOT REPRESENTA-
            TIONS OF PAST OR FUTURE PERFORMANCE OR EXPENSES; ACTUAL PERFOR-
            MANCE AND/OR EXPENSES MAY BE MORE OR LESS THAN SHOWN.
                                                                    Prospectus
                                                                               3
<PAGE>
 
            Financial Highlights

            The following information regarding selected per share data and
            ratios for shares of the Total Return Fund is part of the Trust's
            financial statements, which are included in the Trust's Annual Re-
            port dated March 31, 1998, and incorporated by reference in the
            Statement of Additional Information. The Trust's audited financial
            statements and selected per share data and ratios appearing below
            have been examined by PricewaterhouseCoopers LLP, independent ac-
            countants, whose opinion thereon is also included in the Annual
            Report, which may be obtained without charge.
 
            Selected data for a share outstanding throughout each period:
 
 
 
<TABLE>
<CAPTION>
           TOTAL RETURN FUND--CLASS A                     3/31/98   3/31/97/(a)/
           ---------------------------------------------------------------------
           <S>                                            <C>       <C>
           NET ASSET VALUE, BEGINNING OF PERIOD           $  10.27   $  10.40
                                                          --------   --------
           INCOME FROM INVESTMENT OPERATIONS:
           NET INVESTMENT INCOME                              0.58+      0.12
           NET GAINS OR LOSSES ON SECURITIES (BOTH
            REALIZED AND UNREALIZED)                          0.63+     (0.12)
                                                          --------   --------
           TOTAL INCOME FROM INVESTMENT OPERATIONS            1.21      (0.00)
                                                          --------   --------
           LESS DISTRIBUTIONS:
           DIVIDENDS FROM NET INVESTMENT INCOME              (0.57)     (0.13)
           DIVIDENDS IN EXCESS OF NET INVESTMENT INCOME      (0.02)      0.00
           DIVIDENDS FROM NET REALIZED CAPITAL GAINS         (0.27)      0.00
                                                          --------   --------
           TOTAL DISTRIBUTIONS                               (0.86)     (0.13)
                                                          --------   --------
           NET ASSET VALUE, END OF PERIOD                 $  10.62   $  10.27
                                                          ========   ========
           TOTAL RETURN (WITHOUT SALES CHARGE)               12.11%      0.02%
           RATIOS/SUPPLEMENTAL DATA
           NET ASSETS, END OF PERIOD (IN 000s)            $533,893   $115,742
           RATIO OF EXPENSES TO AVERAGE NET ASSETS            0.90%      0.91%+
           RATIO OF NET INVESTMENT INCOME TO AVERAGE NET
            ASSETS                                            5.46%      6.08%+
           PORTFOLIO TURNOVER RATE                             206%       173%
</TABLE>
 
            a   From commencement of operations, January 13, 1997.
            +   Annualized.
            +   Per share amounts based on average number of shares outstand-
            ing during the period.
 PIMCO Funds: Pacific Investment Management Series
4
<PAGE>
 
            Investment Objective and Policies
 
            The investment objective and general investment policies of the
            Fund are described below. There can be no assurance that the in-
            vestment objective of the Fund will be achieved. For temporary,
            defensive or emergency purposes, the Fund may invest without limit
            in U.S. debt securities, including short-term money market securi-
            ties, when in the opinion of the Adviser it is appropriate to do
            so. It is impossible to predict for how long such alternative
            strategies will be utilized. The value of all securities and other
            instruments held by the Fund will vary from time to time in re-
            sponse to a wide variety of market factors. Consequently, the net
            asset value per share of the Fund will vary.
               The investment objective of the Fund is fundamental and may not
            be changed without shareholder approval by vote of a majority of
            the outstanding shares of the Fund. If there is a change in the
            Fund's investment objective, including a change approved by a
            shareholder vote, shareholders should consider whether the Fund
            remains an appropriate investment in light of their then current
            financial position and needs.
               Specific portfolio securities eligible for purchase by the
            Fund, investment techniques that may be used by the Fund, and the
            risks associated with these securities and techniques are de-
            scribed more fully under "Characteristics and Risks of Securities
            and Investment Techniques" in this Prospectus and "Investment Ob-
            jectives and Policies" in the Statement of Additional Information.
 
 
TOTAL       The investment objective of the Fund is to seek to maximize total
RETURN FUND return, consistent with preservation of capital and prudent in-
DESCRIPTION vestment management.
               In selecting securities for the Fund, the Adviser utilizes eco-
            nomic forecasting, interest rate anticipation, credit and call
            risk analysis, foreign currency exchange rate forecasting, and
            other security selection techniques. The proportion of the Fund's
            assets committed to investment in securities with particular char-
            acteristics (such as maturity, type and coupon rate) will vary
            based on the Adviser's outlook for the U.S. and foreign economies,
            the financial markets, and other factors.
               The Fund invests under normal circumstances at least 65% of its
            assets in a diversified portfolio of the following types of secu-
            rities, which may have a variety of maturities: securities issued
            or guaranteed by the U.S. Government, its agencies or instrumen-
            talities ("U.S. Government securities"); corporate debt securi-
            ties, including convertible securities and corporate commercial
            paper; mortgage-backed and other asset-backed securities; infla-
            tion-indexed bonds issued by both governments and corporations;
            structured notes, including hybrid or "indexed" securities, catas-
            trophe bonds, and loan participations; delayed funding loans and
            revolving credit facilities; bank certificates of deposit, fixed
            time deposits and bankers' acceptances; repurchase agreements and
            reverse repurchase agreements; obligations of foreign governments
            or their subdivisions, agencies and instrumentalities; and obliga-
            tions of international agencies or supranational entities. Fixed
            income securities may have fixed, variable, or floating rates of
            interest, including rates of interest that vary inversely at a
            multiple of a designated or floating rate, or that vary according
            to changes in relative values of currencies.
               The average portfolio duration of the Fund will normally vary
            within a three- to six-year time frame based on the Adviser's
            forecast for interest rates. The Fund may invest up to 10% of its
            assets in fixed income securities that are rated below investment
            grade (i.e., securities rated at least Baa by Moody's Investors
            Service, Inc. ("Moody's") or BBB by Standard & Poor's Ratings
            Services ("S&P")) but rated B or higher by Moody's or S&P (or, if
            unrated, determined by the Adviser to be of comparable quality).
            For information on the risks associated with investments in secu-
            rities rated below investment grade, see "Appendix B--Description
            of Securities Ratings." The Fund may also invest up to 20% of its
            assets in securities denominated in foreign currencies, and may
            invest beyond this limit in U.S. dollar-denominated securities of
            foreign issuers. Portfolio holdings will be concentrated in areas
            of the bond market (based on quality, sector, coupon or maturity)
            which the Adviser believes to be relatively undervalued. The Fund
            may invest all of its assets in derivative instruments or in mort-
            gage- or asset-backed securities.
               The Fund may adhere to its investment policy by entering into a
            series of purchase and sale contracts or utilizing other invest-
            ment techniques by which it may obtain market exposure to the se-
            curities in which it primarily invests. In addition, the Fund may
            lend its portfolio securities to brokers, dealers and other finan-
            cial institutions in order to earn income. The Fund may purchase
            and sell options and futures subject to the limits discussed be-
            low, engage in credit spread trades and enter into forward foreign
            currency contracts.
                                                                    Prospectus
                                                                              5
<PAGE>
 
              As a non-fundamental, operating policy, the Adviser intends to
            use foreign currency-related derivative instruments (currency
            futures and related options, currency options, forward contracts
            and swap agreements) in an effort to hedge foreign currency risk
            with respect to at least 75% of the assets of the Fund denominated
            in currencies other than the U.S. dollar. There can be no assur-
            ance that the Adviser will be successful in doing so. The active
            use of currency derivatives involves transaction costs which may
            adversely affect yield and return.
 
 
 
TOTAL       The "total return" sought by the Fund will consist of interest and
RETURN      dividends from underlying securities, capital appreciation re-
            flected in unrealized increases in value of portfolio securities
            (realized by the shareholder only upon selling shares), or real-
            ized from the purchase and sale of securities and use of futures
            and options, or gains from favorable changes in foreign currency
            exchange rates. Generally, over the long term, the total return
            obtained by a portfolio investing primarily in fixed income secu-
            rities is not expected to be as great as that obtained by a port-
            folio that invests primarily in equity securities. At the same
            time, the market risk and price volatility of a fixed income port-
            folio is expected to be less than that of an equity portfolio, so
            that a fixed income portfolio is generally considered to be a more
            conservative investment. The change in market value of fixed in-
            come securities (and therefore their capital appreciation or de-
            preciation) is largely a function of changes in the current level
            of interest rates.
 
               In managing fixed income securities, one of the principal tools
            generally used by the Adviser is "duration," which is a measure of
            the expected life of a fixed income security on a present value
            basis, incorporating a bond's yield, coupon interest payments, fi-
            nal maturity and call features. See "Appendix A--Description of
            Duration." Generally, when interest rates are falling, a portfolio
            with a shorter duration will not generate as high a level of total
            return as a portfolio with a longer duration. Conversely, when in-
            terest rates are rising, a portfolio with a shorter duration will
            generally outperform longer duration portfolios. When interest
            rates are flat, shorter duration portfolios generally will not
            generate as high a level of total return as longer duration port-
            folios (assuming that long-term interest rates are higher than
            short-term rates, which is commonly the case). With respect to the
            composition of any fixed income portfolio, the longer the duration
            of the portfolio, the greater the anticipated potential for total
            return, with, however, greater attendant market risk and price
            volatility than for a portfolio with a shorter duration. The mar-
            ket value of fixed income securities denominated in currencies
            other than the U.S. dollar also may be affected by movements in
            foreign currency exchange rates.
 
            Investment Risks and Considerations
 
            The following are some of the principal risks of investing in the
            Fund. Investors should read this Prospectus carefully for a more
            complete discussion of the risks relating to an investment in the
            Fund. The net asset value per share of the Fund may be less at the
            time of redemption than it was at the time of investment. General-
            ly, the value of fixed income securities can be expected to vary
            inversely with changes in prevailing interest rates, i.e., as in-
            terest rates rise, market value tends to decrease, and vice versa.
            In addition, the Fund may invest in securities rated lower than
            Baa by Moody's or BBB by S&P. Such securities carry a high degree
            of credit risk and are considered speculative by the major rating
            agencies.
               The Fund may invest in securities of foreign issuers, which may
            be subject to additional risk factors, including foreign currency
            and political risks, not applicable to securities of U.S. issuers.
            The Fund's investment techniques may involve a form of borrowing,
            which may tend to exaggerate the effect on net asset value of any
            increase or decrease in the market value of the Fund's portfolio
            and may require liquidation of portfolio positions when it is not
            advantageous to do so. The Fund may sell securities short, which
            exposes the Fund to a risk of loss if the value of the security
            sold short should increase.
               The Fund may use derivative instruments, consisting of futures,
            options, options on futures, and swap agreements, for hedging pur-
            poses or as part of its investment strategies. Use of these in-
            struments may involve certain costs and risks,
 PIMCO Funds: Pacific Investment Management Series
6
<PAGE>
 
            including the risk that the Fund could not close out a position
            when it would be most advantageous to do so, the risk of an imper-
            fect correlation between the value of the securities being hedged
            and the value of the particular derivative instrument, and the
            risk that unexpected changes in interest rates may adversely af-
            fect the value of the Fund's investments in particular derivative
            instruments. Unless otherwise indicated, all limitations applica-
            ble to the Fund's investments (as stated in this Prospectus and in
            the Statement of Additional Information) apply only at the time a
            transaction is entered into. Any subsequent change in a rating as-
            signed by any rating service to a security (or, if unrated, deemed
            to be of comparable quality), or change in the percentage of the
            Fund's assets invested in certain securities or other instruments,
            or change in the average duration of the Fund's investment portfo-
            lio, resulting from market fluctuations or other changes in the
            Fund's total assets, will not require the Fund to dispose of an
            investment until the Adviser determines that it is practicable to
            sell or close out the investment without undue market or tax con-
            sequences to the Fund. In the event that ratings services assign
            different ratings to the same security, the Adviser will determine
            which rating it believes best reflects the security's quality and
            risk at that time, which may be the higher of the several assigned
            ratings.
               The Fund offers its shares to both retail and institutional in-
            vestors. Institutional shareholders, some of whom also may be in-
            vestment advisory clients of Pacific Investment Management, may
            hold large positions in the Fund. Such shareholders may on occa-
            sion make large redemptions of their holdings in the Fund to meet
            their liquidity needs, in connection with strategic adjustments to
            their overall portfolio of investments, or for other purposes.
            Large redemptions from the Fund could require the Adviser to liq-
            uidate portfolio positions when it is not most desirable to do so.
            Liquidation of portfolio holdings also may cause the Fund to real-
            ize taxable capital gains.
 
            Characteristics and Risks of
            Securities and Investment Techniques
 
            The following describes in greater detail different types of secu-
            rities and investment techniques used by the Fund, and discusses
            certain concepts relevant to the investment policies of the Fund.
            Additional information about the Fund's investments and investment
            practices may be found in the Statement of Additional Information.
 
 
U.S.        U.S. Government securities are obligations of, or guaranteed by,
GOVERNMENT  the U.S. Government, its agencies or instrumentalities. The U.S.
SECURITIES  Government does not guarantee the net asset value of the Fund's
            shares. Some U.S. Government securities, such as Treasury bills,
            notes and bonds, and securities guaranteed by the Government Na-
            tional Mortgage Association ("GNMA"), are supported by the full
            faith and credit of the United States; others, such as those of
            the Federal Home Loan Banks, are supported by the right of the is-
            suer to borrow from the U.S. Treasury; others, such as those of
            the Federal National Mortgage Association ("FNMA"), are supported
            by the discretionary authority of the U.S. Government to purchase
            the agency's obligations; and still others, such as those of the
            Student Loan Marketing Association, are supported only by the
            credit of the instrumentality. U.S. Government securities include
            securities that have no coupons, or have been stripped of their
            unmatured interest coupons, individual interest coupons from such
            securities that trade separately, and evidences of receipt of such
            securities. Such securities may pay no cash income, and are pur-
            chased at a deep discount from their value at maturity. Because
            interest on zero coupon securities is not distributed on a current
            basis but is, in effect, compounded, zero coupon securities tend
            to be subject to greater market risk than interest-paying securi-
            ties of similar maturities. Custodial receipts issued in connec-
            tion with so-called trademark zero coupon securities, such as CATs
            and TIGRs, are not issued by the U.S. Treasury, and are therefore
            not U.S. Government securities, although the underlying bond
            represented by such receipt is a debt obligation of the U.S.
            Treasury. Other zero coupon Treasury securities (STRIPs and CUBEs)
            are direct obligations of the U.S. Government.
                                                                    Prospectus
                                                                               7
<PAGE>
 
 
 
CORPORATE   Corporate debt securities include corporate bonds, debentures,
DEBT        notes and other similar corporate debt instruments, including con-
SECURITIES  vertible securities. Debt securities may be acquired with warrants
            attached. Corporate income-producing securities may also include
            forms of preferred or preference stock. The rate of interest on a
            corporate debt security may be fixed, floating or variable, and
            may vary inversely with respect to a reference rate. See "Variable
            and Floating Rate Securities" below. The rate of return or return
            of principal on some debt obligations may be linked or indexed to
            the level of exchange rates between the U.S. dollar and a foreign
            currency or currencies.
               Investments in corporate debt securities that are rated below
            investment grade (rated below Baa (Moody's) or BBB (S&P)) are de-
            scribed as "speculative" both by Moody's and S&P. Such securities
            are sometimes referred to as "junk bonds," and may be subject to
            greater market fluctuations, less liquidity and greater risk of
            loss of income or principal, including a greater possibility of
            default or bankruptcy of the issuer of such securities, than are
            more highly rated debt securities. Moody's also describes securi-
            ties rated Baa as having speculative characteristics. The Adviser
            seeks to minimize these risks through diversification, in-depth
            credit analysis and attention to current developments in interest
            rates and market conditions. See "Appendix B--Description of Secu-
            rities Ratings." Investments in high yield securities are dis-
            cussed separately below under "High Yield Securities ("Junk
            Bonds")."
 
 
CONVERTIBLE The Fund may invest in convertible securities, which may offer
SECURITIES  higher income than the common stocks into which they are convert-
            ible. Typically, convertible securities are callable by the compa-
            ny, which may, in effect, force conversion before the holder would
            otherwise choose.
               The convertible securities in which the Fund may invest consist
            of bonds, notes, debentures and preferred stocks which may be con-
            verted or exchanged at a stated or determinable exchange ratio
            into underlying shares of common stock. The Fund may be required
            to permit the issuer of a convertible security to redeem the secu-
            rity, convert it into the underlying common stock, or sell it to a
            third party. Thus, the Fund may not be able to control whether the
            issuer of a convertible security chooses to convert that security.
            If the issuer chooses to do so, this action could have an adverse
            effect on the Fund's ability to achieve its investment objectives.
               While the Fund intends to invest primarily in fixed income se-
            curities, it may invest in convertible securities or equity secu-
            rities. While some countries or companies may be regarded as fa-
            vorable investments, pure fixed income opportunities may be unat-
            tractive or limited due to insufficient supply, legal or technical
            restrictions. In such cases, the Fund may consider equity securi-
            ties or convertible bonds to gain exposure to such investments.
 
 
LOAN        The Fund may invest in fixed- and floating-rate loans arranged      
PARTICI-    through private negotiations between an issuer of debt instruments  
PATIONS AND and one or more financial institutions ("lenders"). Generally, the  
ASSIGNMENTS Fund's investments in loans are expected to take the form of loan   
            participations and assignments of portions of loans from third      
            parties.
               Large loans to corporations or governments may be shared or      
            syndicated among several lenders, usually banks. The Fund may par-  
            ticipate in such syndicates, or can buy part of a loan, becoming a  
            direct lender. Participations and assignments involve special       
            types of risk, including limited marketability and the risks of     
            being a lender. See "Illiquid Securities" for a discussion of the   
            limits on the Fund's investments in loan participations and as-     
            signments with limited marketability. If the Fund purchases a par-  
            ticipation, it may only be able to enforce its rights through the   
            lender, and may assume the credit risk of the lender in addition    
            to the borrower. In assignments, the Fund's rights against the      
            borrower may be more limited than those held by the original lend-  
            er.                                                                 
            
            
DELAYED     The Fund may also enter into, or acquire participations in, de-   
FUNDING     layed funding loans and revolving credit facilities. Delayed fund-
LOANS AND   ing loans and revolving credit facilities are borrowing arrange-  
REVOLVING   ments in which the lender agrees to make loans up to a maximum    
CREDIT      amount upon demand by the borrower during a specified term. A re- 
FACILITIES  volving credit facility differs from a delayed funding loan in    
            that as the borrower repays the loan, an amount equal to the re-  
            payment may be borrowed again during the term of the revolving    
            credit facility. These commitments may have the effect of requir- 
            ing the Fund to                                                    
 PIMCO Funds: Pacific Investment Management Series
8
<PAGE>
 
            increase its investment in a company at a time when it might not
            otherwise decide to do so (including at a time when the company's
            financial condition makes it unlikely that such amounts will be
            repaid).
               The Fund may acquire a participation interest in delayed fund-
            ing loans or revolving credit facilities from a bank or other fi-
            nancial institution. See "Loan Participations and Assignments."
            The terms of the participation require the Fund to make a pro rata
            share of all loans extended to the borrower and entitles the Fund
            to a pro rata share of all payments made by the borrower. Delayed
            funding loans and revolving credit facilities usually provide for
            floating or variable rates of interest. To the extent that the
            Fund is committed to advance additional funds, it will at all
            times segregate assets, determined to be liquid by the Adviser in
            accordance with procedures established by the Board of Trustees,
            in an amount sufficient to meet such commitments.
 
 
VARIABLE    Variable and floating rate securities provide for a periodic ad-
AND         justment in the interest rate paid on the obligations. The terms
FLOATING    of such obligations must provide that interest rates are adjusted
RATE        periodically based upon an interest rate adjustment index as pro-
SECURITIES  vided in the respective obligations. The adjustment intervals may
            be regular, and range from daily up to annually, or may be event
            based, such as based on a change in the prime rate.
               The Fund may engage in credit spread trades and invest in
            floating rate debt instruments ("floaters"). A credit spread trade
            is an investment position relating to a difference in the prices
            or interest rates of two securities or currencies, where the value
            of the investment position is determined by movements in the dif-
            ference between the prices or interest rates, as the case may be,
            of the respective securities or currencies. The interest rate on a
            floater is a variable rate which is tied to another interest rate,
            such as a money-market index or Treasury bill rate. The interest
            rate on a floater resets periodically, typically every six months.
            While, because of the interest rate reset feature, floaters pro-
            vide the Fund with a certain degree of protection against rises in
            interest rates, the Fund will participate in any declines in in-
            terest rates as well.
               The Fund may also invest in inverse floating rate debt instru-
            ments ("inverse floaters"). The interest rate on an inverse
            floater resets in the opposite direction from the market rate of
            interest to which the inverse floater is indexed. An inverse
            floating rate security may exhibit greater price volatility than a
            fixed rate obligation of similar credit quality. The Fund has
            adopted a policy under which the Fund will invest no more than 5%
            of its net assets in any combination of inverse floater, interest
            only ("IO"), or principal only ("PO") securities. See "Mortgage-
            Related and Other Asset-Backed Securities" for a discussion of IOs
            and POs.
 
 
INFLATION-  Inflation-indexed bonds are fixed income securities whose princi-
INDEXED     pal value is periodically adjusted according to the rate of infla-
BONDS       tion. Two structures are common. The U.S. Treasury and some other
            issuers use a structure that accrues inflation into the principal
            value of the bond. Most other issuers pay out the CPI accruals as
            part of a semiannual coupon.
               Inflation-indexed securities issued by the U.S. Treasury have
            maturities of five, ten or thirty years, although it is possible
            that securities with other maturities will be issued in the fu-
            ture. The U.S. Treasury securities pay interest on a semi-annual
            basis, equal to a fixed percentage of the inflation-adjusted prin-
            cipal amount. For example, if an investor purchased an inflation-
            indexed bond with a par value of $1,000 and a 3% real rate of re-
            turn coupon (payable 1.5% semi-annually), and inflation over the
            first six months were 1%, the mid-year par value of the bond would
            be $1,010 and the first semi-annual interest payment would be
            $15.15 ($1,010 times 1.5%). If inflation during the second half of
            the year resulted in the whole years' inflation equaling 3%, the
            end-of-year par value of the bond would be $1,030 and the second
            semi-annual interest payment would be $15.45 ($1,030 times 1.5%).
               If the periodic adjustment rate measuring inflation falls, the
            principal value of inflation-indexed bonds will be adjusted down-
            ward, and consequently the interest payable on these securities
            (calculated with respect to a smaller principal amount) will be
            reduced. Repayment of the original bond principal upon maturity
            (as adjusted for inflation) is guaranteed in the case of U.S.
            Treasury inflation-indexed bonds, even during a period of defla-
            tion. However, the current market value of the bonds is not guar-
            anteed, and will fluctuate. The Fund may also invest in other in-
            flation
                                                                    Prospectus
                                                                               9
<PAGE>
 
            related bonds which may or may not provide a similar guarantee. If
            such a guarantee of principal is not provided, the adjusted prin-
            cipal value of the bond repaid at maturity may be less than the
            original principal.
               The value of inflation-indexed bonds is expected to change in
            response to changes in real interest rates. Real interest rates in
            turn are tied to the relationship between nominal interest rates
            and the rate of inflation. Therefore, if inflation were to rise at
            a faster rate than nominal interest rates, real interest rates
            might decline, leading to an increase in value of inflation-in-
            dexed bonds. In contrast, if nominal interest rates increased at a
            faster rate than inflation, real interest rates might rise, lead-
            ing to a decrease in value of inflation-indexed bonds.
               While these securities are expected to be protected from long-
            term inflationary trends, short-term increases in inflation may
            lead to a decline in value. If interest rates rise due to reasons
            other than inflation (for example, due to changes in currency ex-
            change rates), investors in these securities may not be protected
            to the extent that the increase is not reflected in the bond's in-
            flation measure.
               The periodic adjustment of U.S. inflation-indexed bonds is tied
            to the Consumer Price Index for Urban Consumers ("CPI-U"), which
            is calculated monthly by the U.S. Bureau of Labor Statistics. The
            CPI-U is a measurement of changes in the cost of living, made up
            of components such as housing, food, transportation and energy.
            Inflation-indexed bonds issued by a foreign government are gener-
            ally adjusted to reflect a comparable inflation index, calculated
            by that government. There can be no assurance that the CPI-U or
            any foreign inflation index will accurately measure the real rate
            of inflation in the prices of goods and services. Moreover, there
            can be no assurance that the rate of inflation in a foreign coun-
            try will be correlated to the rate of inflation in the United
            States.
 
MORTGAGE-   The Fund may invest all of its assets in mortgage- or other asset-
RELATED AND backed securities. The value of some mortgage- or asset-backed se-
OTHER       curities in which the Fund invests may be particularly sensitive
ASSET-      to changes in prevailing interest rates, and, like the other in-
BACKED      vestments of the Fund, the ability of the Fund to successfully
SECURITIES  utilize these instruments may depend in part upon the ability of
            the Adviser to forecast interest rates and other economic factors
            correctly.
 
            MORTGAGE-PASS-THROUGH SECURITIES are securities representing in-
            terests in "pools" of mortgage loans secured by residential or
            commercial real property in which payments of both interest and
            principal on the securities are generally made monthly, in effect
            "passing through" monthly payments made by the individual borrow-
            ers on the mortgage loans which underlie the securities (net of
            fees paid to the issuer or guarantor of the securities). Early re-
            payment of principal on some mortgage-related securities (arising
            from prepayments of principal due to sale of the underlying prop-
            erty, refinancing, or foreclosure, net of fees and costs which may
            be incurred) may expose the Fund to a lower rate of return upon
            reinvestment of principal. Also, if a security subject to prepay-
            ment has been purchased at a premium, the value of the premium
            would be lost in the event of prepayment. Like other fixed income
            securities, when interest rates rise, the value of a mortgage-re-
            lated security generally will decline; however, when interest
            rates are declining, the value of mortgage-related securities with
            prepayment features may not increase as much as other fixed income
            securities. The rate of prepayments on underlying mortgages will
            affect the price and volatility of a mortgage-related security,
            and may have the effect of shortening or extending the effective
            maturity of the security beyond what was anticipated at the time
            of purchase. To the extent that unanticipated rates of prepayment
            on underlying mortgages increase the effective maturity of a mort-
            gage-related security, the volatility of such security can be ex-
            pected to increase.
               Payment of principal and interest on some mortgage pass-through
            securities (but not the market value of the securities themselves)
            may be guaranteed by the full faith and credit of the U.S. Govern-
            ment (in the case of securities guaranteed by GNMA); or guaranteed
            by agencies or instrumentalities of the U.S. Government (in the
            case of securities guaranteed by FNMA or the Federal Home Loan
            Mortgage Corporation ("FHLMC"), which are supported only by the
            discretionary authority of the U.S. Government to purchase the
            agency's obligations). Mortgage-related securities created by non-
            governmental issuers (such as commercial banks, savings and loan
            institutions, private mortgage insurance companies, mortgage bank-
            ers and other secondary market issuers) may be supported by vari-
            ous forms of insurance or guarantees, including individual loan,
            title, pool and hazard insurance and letters of credit, which may
            be issued by governmental entities, private insurers or the mort-
            gage poolers.
 
 
10
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            COLLATERALIZED MORTGAGE OBLIGATIONS ("CMOs") are hybrid mortgage-
            related instruments. Interest and pre-paid principal on a CMO are
            paid, in most cases, on a monthly basis. CMOs may be collateral-
            ized by whole mortgage loans but are more typically collateralized
            by portfolios of mortgage pass-through securities guaranteed by
            GNMA, FHLMC, or FNMA. CMOs are structured into multiple classes,
            with each class bearing a different stated maturity. Monthly pay-
            ments of principal, including prepayments, are first returned to
            investors holding the shortest maturity class; investors holding
            the longer maturity classes receive principal only after the first
            class has been retired. CMOs that are issued or guaranteed by the
            U.S. Government or by any of its agencies or instrumentalities
            will be considered U.S. Government securities by the Fund, while
            other CMOs, even if collateralized by U.S. Government securities,
            will have the same status as other privately issued securities for
            purposes of applying the Fund's diversification tests.
 
            COMMERCIAL MORTGAGE-BACKED SECURITIES include securities that re-
            flect an interest in, and are secured by, mortgage loans on com-
            mercial real property. The market for commercial mortgage-backed
            securities developed more recently and in terms of total outstand-
            ing principal amount of issues is relatively small compared to the
            market for residential single-family mortgage-backed securities.
            Many of the risks of investing in commercial mortgage-backed secu-
            rities reflect the risks of investing in the real estate securing
            the underlying mortgage loans. These risks reflect the effects of
            local and other economic conditions on real estate markets, the
            ability of tenants to make loan payments, and the ability of a
            property to attract and retain tenants. Commercial mortgage-backed
            securities may be less liquid and exhibit greater price volatility
            than other types of mortgage-related or asset-backed securities.
 
            MORTGAGE-RELATED SECURITIES include securities other than those
            described above that directly or indirectly represent a participa-
            tion in, or are secured by and payable from, mortgage loans on
            real property, such as mortgage dollar rolls (see "Reverse Repur-
            chase Agreements, Dollar Rolls, and Borrowings"), CMO residuals or
            stripped mortgage-backed securities ("SMBS"), and may be struc-
            tured in classes with rights to receive varying proportions of
            principal and interest.
               A common type of SMBS will have one class receiving some of the
            interest and most of the principal from the mortgage assets, while
            the other class will receive most of the interest and the remain-
            der of the principal. In the most extreme case, one class will re-
            ceive all of the interest (the interest-only, or "IO" class),
            while the other class will receive all of the principal (the prin-
            cipal-only, or "PO" class). The yield to maturity on an IO class
            is extremely sensitive to the rate of principal payments (includ-
            ing prepayments) on the related underlying mortgage assets, and a
            rapid rate of principal payments may have a material adverse ef-
            fect on the Fund's yield to maturity from these securities. The
            Fund has adopted a policy under which the Fund will invest no more
            than 5% of its net assets in any combination of IO, PO, or inverse
            floater securities. The Fund may invest in other asset-backed se-
            curities that have been offered to investors. For a discussion of
            the characteristics of some of these instruments, see the State-
            ment of Additional Information.
 
REPURCHASE  For the purpose of achieving income, the Fund may enter into re-
AGREEMENTS  purchase agreements, which entail the purchase of a portfolio-eli-
            gible security from a bank or broker-dealer that agrees to repur-
            chase the security at the Fund's cost plus interest within a spec-
            ified time (normally one day). If the party agreeing to repurchase
            should default, as a result of bankruptcy or otherwise, the Fund
            will seek to sell the securities which it holds, which action
            could involve procedural costs or delays in addition to a loss on
            the securities if their value should fall below their repurchase
            price. The Fund will invest no more than 15% of its net assets
            (taken at current market value) in repurchase agreements maturing
            in more than seven days.
 
REVERSE     A reverse repurchase agreement involves the sale of a security by
REPURCHASE  the Fund and its agreement to repurchase the instrument at a spec-
AGREEMENTS, ified time and price. Under a reverse repurchase agreement, the
DOLLAR      Fund continues to receive any principal and interest payments on
ROLLS, AND  the underlying security during the term of the agreement. The Fund
BORROWINGS  generally will segregate assets determined to be liquid by the Ad-
            viser in accordance with procedures established by the Board of
            Trustees to cover its obligations under reverse repurchase agree-
            ments and, to this extent, a reverse repurchase agreement
 
                                                                             11
                                                                    Prospectus
<PAGE>
 
            (or economically similar transaction) will not be considered a
            "senior security" subject to the 300% asset coverage requirements
            otherwise applicable to borrowings by the Fund.
               The Fund may enter into dollar rolls, in which the Fund sells
            mortgage-backed or other securities for delivery in the current
            month and simultaneously contracts to purchase substantially simi-
            lar securities on a specified future date. In the case of dollar
            rolls involving mortgage-backed securities, the mortgage-backed
            securities that are purchased will be of the same type and will
            have the same interest rate as those sold, but will be supported
            by different pools of mortgages. The Fund forgoes principal and
            interest paid during the roll period on the securities sold in a
            dollar roll, but the Fund is compensated by the difference between
            the current sales price and the lower price for the future pur-
            chase as well as by any interest earned on the proceeds of the se-
            curities sold. The Fund also could be compensated through the re-
            ceipt of fee income equivalent to a lower forward price. The Fund
            will segregate assets determined to be liquid by the Adviser in
            accordance with procedures established by the Board of Trustees to
            cover its obligations under dollar rolls.
               To the extent that positions in reverse repurchase agreements,
            dollar rolls or similar transactions are not covered through the
            maintenance of segregated liquid assets at least equal to the
            amount of any forward purchase commitment, such transactions would
            be subject to the Fund's limitations on borrowings, which would
            restrict the aggregate of such transactions (plus any other
            borrowings) to 33 1/3% of the Fund's total assets. Apart from such
            transactions, the Fund will not borrow money, except for temporary
            administrative purposes.
 
 
LOANS OF    For the purpose of achieving income, the Fund may lend its portfo-
PORTFOLIO   lio securities to brokers, dealers, and other financial institu-
SECURITIES  tions, provided:
                (i)   the loan is secured continuously by collateral consisting
                      of U.S. Government securities, cash or cash equivalents
                      (nego-tiable certificates of deposit, bankers' acceptances
                      or let-ters of credit) maintained on a daily mark-to-
                      market basis in an amount at least equal to the current
                      market value of the securities loaned;
                (ii)  the Fund may at any time call the loan and obtain the
                      return of the securities loaned;
                (iii) the Fund will receive any interest or dividends paid on
                      the loaned securities; and
                (iv)  the aggregate market value of securities loaned will not
                      at any time exceed 33 1/3% of the total assets of the
                      Fund.
            The Fund's performance will continue to reflect changes in the
            value of the securities loaned and will also reflect the receipt
            of either interest, through investment of cash collateral by the
            Fund in permissible investments, or a fee, if the collateral is
            U.S. Government securities. Securities lending involves the risk
            of loss of rights in the collateral or delay in recovery of the
            collateral should the borrower fail to return the security loaned
            or become insolvent. The Fund may pay lending fees to the party
            arranging the loan.
 
 
WHEN-       The Fund may purchase or sell securities on a when-issued, delayed
ISSUED,     delivery, or forward commitment basis. These transactions involve
DELAYED     a commitment by the Fund to purchase or sell securities for a pre-
DELIVERY    determined price or yield, with payment and delivery taking place
AND FORWARD more than seven days in the future, or after a period longer than
COMMITMENT  the customary settlement period for that type of security. When
TRANS-      such purchases are outstanding, the Fund will segregate until the
ACTIONS     settlement date assets determined to be liquid by the Adviser in
            accordance with procedures established by the Board of Trustees,
            in an amount sufficient to meet the purchase price. Typically, no
            income accrues on securities the Fund has committed to purchase
            prior to the time delivery of the securities is made, although the
            Fund may earn income on securities it has segregated.
               When purchasing a security on a when-issued, delayed delivery,
            or forward commitment basis, the Fund assumes the rights and risks
            of ownership of the security, including the risk of price and
            yield fluctuations, and takes such fluctuations into account when
            determining its net asset value. Because the Fund is not required
            to pay for the security until the delivery date, these risks are
            in addition to the risks associated with the Fund's other invest-
            ments. If the Fund remains substantially fully invested at a time
            when when-issued, delayed delivery, or forward commitment pur-
            chases are outstanding, the purchases may result in a form of lev-
            erage.
 
12
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               When the Fund has sold a security on a when-issued, delayed de-
            livery, or forward commitment basis, the Fund does not participate
            in future gains or losses with respect to the security. If the
            other party to a transaction fails to deliver or pay for the secu-
            rities, the Fund could miss a favorable price or yield opportunity
            or could suffer a loss. The Fund may dispose of or renegotiate a
            transaction after it is entered into, and may sell when-issued,
            delayed delivery or forward commitment securities before they are
            delivered, which may result in a capital gain or loss. There is no
            percentage limitation on the extent to which the Fund may purchase
            or sell securities on a when-issued, delayed delivery, or forward
            commitment basis.
 
 
SHORT SALES The Fund may from time to time effect short sales as part of its
            overall portfolio management strategies, including the use of de-
            rivative instruments, or to offset potential declines in value of
            long positions in similar securities as those sold short. A short
            sale (other than a short sale against the box) is a transaction in
            which the Fund sells a security it does not own at the time of the
            sale in anticipation that the market price of that security will
            decline. To the extent that the Fund engages in short sales, it
            must (except in the case of short sales "against the box") main-
            tain asset coverage in the form of segregated assets determined to
            be liquid by the Adviser in accordance with procedures established
            by the Board of Trustees or otherwise cover its position in a per-
            missible manner. A short sale is "against the box" to the extent
            that the Fund contemporaneously owns, or has the right to obtain
            at no added cost, securities identical to those sold short.
 
 
FOREIGN     The Fund may invest directly in fixed income securities of non-
SECURITIES  U.S. issuers. The Fund will concentrate its investments in securi-
            ties of issuers based in developed countries; however, the Fund
            may invest up to 10% of its assets in securities of issuers based
            in emerging market countries.
               Individual foreign economies may differ favorably or unfavor-
            ably from the U.S. economy in such respects as growth of gross do-
            mestic product, rate of inflation, capital reinvestment, re-
            sources, self-sufficiency and balance of payments positions. The
            securities markets, values of securities, yields and risks associ-
            ated with securities markets in differ- ent countries may change
            independently of each other. Investing in the securities of is-
            suers in any foreign country involves special risks and considera-
            tions not typically associated with investing in U.S. companies.
            Shareholders should consider carefully the substantial risks in-
            volved in investing in securities issued by companies and govern-
            ments of foreign nations. These risks include: differences in ac-
            counting, auditing and financial reporting standards; generally
            higher commission rates on foreign portfolio transactions; the
            possibility of nationalization, expropriation or confiscatory tax-
            ation; adverse changes in investment or exchange control regula-
            tions (which may include suspension of the ability to transfer
            currency from a country); and political instability which could
            affect U.S. investments in foreign countries. Additionally, for-
            eign securities and dividends and interest payable on those secu-
            rities may be subject to foreign taxes, including taxes withheld
            from payments on those securities. Foreign securities often trade
            with less frequency and volume than domestic securities and there-
            fore may exhibit greater price volatility. Additional costs asso-
            ciated with an investment in foreign securities may include higher
            custodial fees than apply to domestic custodial arrangements and
            transaction costs of foreign currency conversions. Changes in for-
            eign exchange rates also will affect the value of securities de-
            nominated or quoted in currencies other than the U.S. dollar.
               The Fund may invest in the securities of issuers based in coun-
            tries with developing economies. Investing in developing (or
            "emerging market") countries involves certain risks not typically
            associated with investing in U.S. securities, and imposes risks
            greater than, or in addition to, risks of investing in foreign,
            developed countries. A number of emerging market countries re-
            strict, to varying degrees, foreign investment in securities. Re-
            patriation of investment income, capital, and the proceeds of
            sales by foreign investors may require governmental registration
            and/or approval in some emerging market countries. A number of the
            currencies of emerging market countries have experienced signifi-
            cant declines against the U.S. dollar in recent years, and devalu-
            ation may occur subsequent to investment in these currencies by
            the Fund. Inflation and rapid fluctuations in inflation rates have
            had, and may continue to have, negative effects on the economies
            and securities markets of certain emerging market countries. Many
            of the emerging securities markets are relatively small, have low
            trading volumes, suffer periods of relative illiquidity, and are
            characterized by significant price
                                                                    Prospectus
                                                                              13
<PAGE>
 
            volatility. There is a risk in emerging market countries that a
            future economic or political crisis could lead to price controls,
            forced mergers of companies, expropriation or confiscatory taxa-
            tion, seizure, nationalization, or creation of government monopo-
            lies, any of which may have a detrimental effect on the Fund's in-
            vestment.
               Additional risks of investing in emerging market countries may
            include: currency exchange rate fluctuations; greater social, eco-
            nomic and political uncertainty and instability (including the
            risk of war); more substantial governmental involvement in the
            economy; less governmental supervision and regulation of the secu-
            rities markets and participants in those markets; unavailability
            of currency hedging techniques in certain emerging market coun-
            tries; the fact that companies in emerging market countries may be
            newly organized and may be smaller and less seasoned companies;
            the difference in, or lack of, auditing and financial reporting
            standards, which may result in unavailability of material informa-
            tion about issuers; the risk that it may be more difficult to ob-
            tain and/or enforce a judgment in a court outside the United
            States; and significantly smaller market capitalization of securi-
            ties markets. Also, any change in the leadership or policies of
            Eastern European countries, or the countries that exercise a sig-
            nificant influence over those countries, may halt the expansion of
            or reverse the liberalization of foreign investment policies now
            occurring and adversely affect existing investment opportunities.
               Emerging securities markets may have different clearance and
            settlement procedures, which may be unable to keep pace with the
            volume of securities transactions or otherwise make it difficult
            to engage in such transactions. Settlement problems may cause the
            Fund to miss attractive investment opportunities, hold a portion
            of its assets in cash pending investment, or delay in disposing of
            a portfolio security. Such a delay could result in possible lia-
            bility to a purchaser of the security.
               The Fund may invest in Brady Bonds, which are securities cre-
            ated through the exchange of existing commercial bank loans to
            sovereign entities for new obligations in connection with debt
            restructurings under a debt restructuring plan introduced by for-
            mer U.S. Secretary of the Treasury, Nicholas F. Brady. Brady Bonds
            have been issued only recently, and for that reason do not have a
            long payment history. Brady Bonds may be collateralized or
            uncollateralized, are issued in various currencies (but primarily
            the U.S. dollar), and are actively traded in the over-the-counter
            secondary market. Brady Bonds are not considered to be U.S. Gov-
            ernment securities. In light of the residual risk of Brady Bonds
            and, among other factors, the history of defaults with respect to
            commercial bank loans by public and private entities in countries
            issuing Brady Bonds, investments in Brady Bonds may be viewed as
            speculative. There can be no assurance that Brady Bonds acquired
            by the Fund will not be subject to restructuring arrangements or
            to requests for new credit, which may cause the Fund to suffer a
            loss of interest or principal on any of its holdings. For further
            information, see the Statement of Additional Information.
               The Fund's investments in foreign currency denominated debt ob-
            ligations and hedging activities will likely produce a difference
            between its book income and its taxable income. This difference
            may cause a portion of the Fund's income distributions to consti-
            tute returns of capital for tax purposes or require the Fund to
            make distributions exceeding book income to qualify as a regulated
            investment company for federal tax purposes.
 
 
FOREIGN     Foreign currency exchange rates may fluctuate significantly over
CURRENCY    short periods of time. They generally are determined by the forces
TRANS-      of supply and demand in the foreign exchange markets and the rela-
ACTIONS     tive merits of investments in different countries, actual or per-
            ceived changes in interest rates and other complex factors, as
            seen from an international perspective. Currency exchange rates
            also can be affected unpredictably by intervention (or the failure
            to intervene) by U.S. or foreign governments or central banks, by
            currency controls or political developments in the U.S. or abroad.
            For example, significant uncertainty surrounds the proposed
            intoduction of the euro (a common currency unit for the European
            Union) in January 1999 and its effect on the value of securities
            denominated in local European currencies. These and other curren-
            cies in which the Fund's assets are denominated may be devalued
            against the U.S. dollar, resulting in a loss to the Fund.
               The Fund may buy and sell foreign currencies on a spot and for-
            ward basis to reduce the risks of adverse changes in foreign ex-
            change rates. A forward foreign currency exchange contract in-
            volves an obligation to purchase or sell a
 
14
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            specific currency at a future date, which may be any fixed number
            of days from the date of the contract agreed upon by the parties,
            at a price set at the time of the contract. By entering into a
            forward foreign currency exchange contract, the Fund "locks in"
            the exchange rate between the currency it will deliver and the
            currency it will receive for the duration of the contract. As a
            result, the Fund reduces its exposure to changes in the value of
            the currency it will deliver and increases its exposure to changes
            in the value of the currency it will exchange into. The effect on
            the value of the Fund is similar to selling securities denominated
            in one currency and purchasing securities denominated in another.
            Contracts to sell foreign currency would limit any potential gain
            which might be realized by the Fund if the value of the hedged
            currency increases. The Fund may enter into these contracts for
            the purpose of hedging against foreign exchange risk arising from
            the Fund's investment or anticipated investment in securities de-
            nominated in foreign currencies. The Fund also may enter into
            these contracts for purposes of increasing exposure to a foreign
            currency or to shift exposure to foreign currency fluctuations
            from one country to another. The Fund may use one currency (or a
            basket of currencies) to hedge against adverse changes in the
            value of another currency (or a basket of currencies) when ex-
            change rates between the two currencies are positively correlated.
            The Fund will segregate assets determined to be liquid by the Ad-
            viser in accordance with procedures established by the Board of
            Trustees, to cover its obligations under forward foreign currency
            exchange contracts entered into for non-hedging purposes.
               The Fund may invest in options on foreign currencies and for-
            eign currency futures and options thereon. The Fund also may in-
            vest in foreign currency exchange-related securities, such as for-
            eign currency warrants and other instruments whose return is
            linked to foreign currency exchange rates. The Fund will use these
            techniques to hedge at least 75% of its exposure to foreign cur-
            rency. For a description of these instruments, see "Derivative In-
            struments" below and the Statement of Additional Information.
 
 
HIGH YIELD  The Fund may invest up to 10% of its assets in fixed income secu-
SECURITIES  rities rated lower than Baa by Moody's or lower than BBB by S&P
("JUNK      but rated at least B by Moody's or S&P (or, if not rated, of com-
BONDS")     parable quality). Securities rated lower than Baa by Moody's or
            lower than BBB by S&P are sometimes referred to as "high yield" or
            "junk" bonds. Securities rated Baa are considered by Moody's to
            have some speculative characteristics. Investors should consider
            the following risks associated with high yield securities before
            investing in the Fund.
               Investing in high yield securities involves special risks in
            addition to the risks associated with investments in higher rated
            fixed income securities. High yield securities may be regarded as
            predominately speculative with respect to the issuer's continuing
            ability to meet principal and interest payments. Analysis of the
            creditworthiness of issuers of high yield securities may be more
            complex than for issuers of higher quality debt securities, and
            the ability of the Fund to achieve its investment objective may,
            to the extent of its investments in high yield securities, be more
            dependent upon such creditworthiness analysis than would be the
            case if the Fund were investing in higher quality securities.
               High yield securities may be more susceptible to real or per-
            ceived adverse economic and competitive industry conditions than
            higher grade securities. The prices of high yield securities have
            been found to be less sensitive to interest rate changes than more
            highly rated investments, but more sensitive to adverse economic
            downturns or individual corporate developments. A projection of an
            economic downturn or of a period of rising interest rates, for ex-
            ample, could cause a decline in high yield security prices because
            the advent of a recession could lessen the ability of a highly
            leveraged company to make principal and interest payments on its
            debt securities. If the issuer of high yield securities defaults,
            the Fund may incur additional expenses to seek recovery. In the
            case of high yield securities structured as zero coupon or pay-
            ment-in-kind securities, the market prices of such securities are
            affected to a greater extent by interest rate changes, and there-
            fore tend to be more volatile than securities which pay interest
            periodically and in cash. The secondary markets on which high
            yield securities are traded may be less liquid than the market for
            higher grade securities. Less liquidity in the secondary trading
            markets could adversely affect and cause large fluctuations in the
            daily net asset value of the Fund's shares. Adverse publicity and
            investor perceptions, whether or not based on fundamental analy-
            sis, may decrease the values and liquidity of high yield securi-
            ties, especially in a thinly traded market.
               The use of credit ratings as the sole method of evaluating high
            yield securities can involve certain risks. For
                                                                    Prospectus
                                                                              15
<PAGE>
 
            example, credit ratings evaluate the safety of principal and in-
            terest payments, not the market value risk of high yield securi-
            ties. Also, credit rating agencies may fail to change credit rat-
            ings in a timely fashion to reflect events since the security was
            last rated. The Adviser does not rely solely on credit ratings
            when selecting securities for the Fund, and develops its own inde-
            pendent analysis of issuer credit quality. If a credit rating
            agency changes the rating of a portfolio security held by the
            Fund, the Fund may retain the portfolio security if the Adviser
            deems it in the best interest of shareholders.
               During the year ended March 31, 1998, based upon the dollar-
            weighted average ratings of the Fund's portfolio holdings at the
            end of each month in the Fund's fiscal year, the Fund had the fol-
            lowing percentages of its net assets invested in securities rated
            in the categories indicated as rated by Moody's (or, if unrated,
            determined by the Adviser to be of comparable quality). See "Ap-
            pendix B--Description of Securities Ratings," for further informa-
            tion.
 
 
              FIXED INCOME SECURITIES RATINGS
 
<TABLE>
<CAPTION>
                                                     Below
           Prime 1     Aaa       Aa        A         Prime 1       Baa       Ba        B
           -------------------------------------------------------------------------------
           <S>         <C>       <C>       <C>       <C>           <C>       <C>       <C>
           20%         47%       0%        13%       6%            8%        6%        0%
</TABLE>
 
 
               These figures are intended solely to provide disclosure about
            the Fund's asset composition during its most recent fiscal year.
            The asset composition after this time may or may not be approxi-
            mately the same as represented by such figures. In addition, the
            categories reflect ratings by Moody's, and ratings assigned by S&P
            may not be consistent with ratings assigned by Moody's or other
            credit ratings services, and the Adviser may not necessarily agree
            with a rating assigned by any credit rating agency.
 
 
DERIVATIVE  The Fund may purchase and write call and put options on securi-
INSTRUMENTS ties, securities indexes and foreign currencies, and enter into
            futures contracts and use options on futures contracts as further
            described below. The Fund also may enter into swap agreements with
            respect to foreign currencies, interest rates, and securities in-
            dexes. The Fund may use these techniques to hedge against changes
            in interest rates, foreign currency exchange rates or securities
            prices or as part of its overall investment strategies. The Fund
            may also purchase and sell options relating to foreign currencies
            for purposes of increasing exposure to a foreign currency or to
            shift exposure to foreign currency fluctuations from one country
            to another. The Fund will segregate assets determined to be liquid
            by the Adviser in accordance with procedures established by the
            Board of Trustees (or, as permitted by applicable regulation, en-
            ter into certain offsetting positions) to cover its obligations
            under options, futures, and swaps to avoid leveraging of the Fund.
               The Fund considers derivative instruments to consist of securi-
            ties or other instruments whose value is derived from or related
            to the value of some other instrument or asset, and not to include
            those securities whose payment of principal and/or interest de-
            pends upon cash flows from underlying assets, such as mortgage-re-
            lated or asset-backed securities. The Fund may invest all of its
            assets in derivative instruments.The value of some derivative in-
            struments in which the Fund invests may be particularly sensitive
            to changes in prevailing interest rates, and, like the other in-
            vestments of the Fund, the ability of the Fund to successfully
            utilize these instruments may depend in part upon the ability of
            the Adviser to forecast interest rates and other economic factors
            correctly. If the Adviser incorrectly forecasts such factors and
            has taken positions in derivative instruments contrary to prevail-
            ing market trends, the Fund could be exposed to the risk of loss.
               The Fund might not employ any of the strategies described be-
            low, and no assurance can be given that any strategy used will
            succeed. If the Adviser incorrectly forecasts interest rates, mar-
            ket values or other economic factors in utilizing a derivatives
            strategy for the Fund, the Fund might have been in a better posi-
            tion if it had not entered into the transaction at all. Also,
            suitable derivative transactions may not be available in all cir-
            cumstances. The use of these strategies involves certain special
            risks, including a possible imperfect correlation, or even no cor-
            relation, between price
 
16
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            movements of derivative instruments and price movements of related
            investments. While some strategies involving derivative instru-
            ments can reduce the risk of loss, they can also reduce the oppor-
            tunity for gain or even result in losses by offsetting favorable
            price movements in related investments, or due to the possible in-
            ability of the Fund to purchase or sell a portfolio security at a
            time that otherwise would be favorable for it to do so, or the
            possible need for the Fund to sell a portfolio security at a dis-
            advantageous time, because the Fund is required to maintain asset
            coverage or offsetting positions in connection with transactions
            in derivative instruments, and the possible inability of the Fund
            to close out or to liquidate its derivatives positions. In addi-
            tion, the Fund's use of such instruments may cause the Fund to re-
            alize higher amounts of short-term capital gains (generally taxed
            at ordinary income tax rates) than if it had not used such instru-
            ments.
 
            OPTIONS ON SECURITIES, SECURITIES INDEXES, AND CURRENCIES The Fund
            may purchase put options on securities and indexes. One purpose of
            purchasing put options is to protect holdings in an underlying or
            related security against a substantial decline in market value.
            The Fund may also purchase call options on securities and indexes.
            One purpose of purchasing call options is to protect against sub-
            stantial increases in prices of securities the Fund intends to
            purchase pending its ability to invest in such securities in an
            orderly manner. An option on a security (or index) is a contract
            that gives the holder of the option, in return for a premium, the
            right to buy from (in the case of a call) or sell to (in the case
            of a put) the writer of the option the security underlying the op-
            tion (or the cash value of the index) at a specified exercise
            price at any time during the term of the option. The writer of an
            option on a security has the obligation upon exercise of the op-
            tion to deliver the underlying security upon payment of the exer-
            cise price or to pay the exercise price upon delivery of the un-
            derlying security. Upon exercise, the writer of an option on an
            index is obligated to pay the difference between the cash value of
            the index and the exercise price multiplied by the specified mul-
            tiplier for the index option. An index is designed to reflect
            specified facets of a particular financial or securities market, a
            specific group of financial instruments or securities, or certain
            economic indicators.
               The Fund may sell put or call options it has previously pur-
            chased, which could result in a net gain or loss depending on
            whether the amount realized on the sale is more or less than the
            premium and other transaction costs paid on the put or call option
            which is sold. The Fund may write a call or put option only if the
            option is "covered" by the Fund holding a position in the under-
            lying securities or by other means which would permit immediate
            satisfaction of the Fund's obligation as writer of the option.
            Prior to exercise or expiration, an option may be closed out by an
            offsetting purchase or sale of an option of the same series.
               The Fund may write covered straddles consisting of a combina-
            tion of a call and a put written on the same underlying security.
            A straddle will be covered when sufficient assets are deposited to
            meet the Fund's immediate obligations. The Fund may use the same
            liquid assets to cover both the call and put options where the ex-
            ercise price of the call and put are the same, or the exercise
            price of the call is higher than that of the put. In such cases,
            the Fund will also segregate liquid assets equivalent to the
            amount, if any, by which the put is "in the money."
               The purchase and writing of options involves certain risks.
            During the option period, the covered call writer has, in return
            for the premium on the option, given up the opportunity to profit
            from a price increase in the underlying security above the exer-
            cise price, but, as long as its obligation as a writer continues,
            has retained the risk of loss should the price of the underlying
            security decline. The writer of an option has no control over the
            time when it may be required to fulfill its obligation as a writer
            of the option. Once an option writer has received an exercise no-
            tice, it cannot effect a closing purchase transaction in order to
            terminate its obligation under the option and must deliver the un-
            derlying security at the exercise price. If a put or call option
            purchased by the Fund is not sold when it has remaining value, and
            if the market price of the underlying security remains equal to or
            greater than the exercise price (in the case of a put), or remains
            less than or equal to the exercise price (in the case of a call),
            the Fund will lose its entire investment in the option. Also,
            where a put or call option on a particular security is purchased
            to hedge against price movements in a related security, the price
            of the put or call option may move more or less than the price of
            the related security. There can be no assurance that a liquid mar-
            ket will exist when the Fund seeks to close out an option posi-
            tion.
                                                                    Prospectus
                                                                              17
<PAGE>
 
            Furthermore, if trading restrictions or suspensions are imposed on
            the options markets, the Fund may be unable to close out a posi-
            tion.
               The Fund may buy or sell put and call options on foreign cur-
            rencies. Currency options traded on U.S. or other exchanges may be
            subject to position limits which may limit the ability of the Fund
            to reduce foreign currency risk using such options. Over-the-
            counter options differ from traded options in that they are two-
            party contracts, with price and other terms negotiated between
            buyer and seller, and generally do not have as much market liquid-
            ity as exchange-traded options. The Fund may be required to treat
            as illiquid over-the-counter options purchased and securities be-
            ing used to cover certain written over-the-counter options.
 
            SWAP AGREEMENTS The Fund may enter into interest rate, index, eq-
            uity and currency exchange rate swap agreements. These transac-
            tions would be entered into in an attempt to obtain a particular
            return when it is considered desirable to do so, possibly at a
            lower cost to the Fund than if the Fund had invested directly in
            the asset that yielded the desired return. Swap agreements are
            two-party contracts entered into primarily by institutional in-
            vestors for periods ranging from a few weeks to more than one
            year. In a standard swap transaction, two parties agree to ex-
            change the returns (or differentials in rates of return) earned or
            realized on particular predetermined investments or instruments,
            which may be adjusted for an interest factor. The gross returns to
            be exchanged or "swapped" between the parties are generally calcu-
            lated with respect to a "notional amount," i.e., the return on or
            increase in value of a particular dollar amount invested at a par-
            ticular interest rate, in a particular foreign currency, or in a
            "basket" of securities representing a particular index. Forms of
            swap agreements include interest rate caps, under which, in return
            for a premium, one party agrees to make payments to the other to
            the extent that interest rates exceed a specified rate, or "cap";
            interest rate floors, under which, in return for a premium, one
            party agrees to make payments to the other to the extent that in-
            terest rates fall below a specified level, or "floor"; and inter-
            est rate collars, under which a party sells a cap and purchases a
            floor or vice versa in an attempt to protect itself against inter-
            est rate movements exceeding given minimum or maximum levels.
               Most swap agreements entered into by the Fund calculate the ob-
            ligations of the parties to the agreement on a "net basis." Conse-
            quently, the Fund's current obligations (or rights) under a swap
            agreement will generally be equal only to the net amount to be
            paid or received under the agreement based on the relative values
            of the positions held by each party to the agreement (the "net
            amount"). The Fund's current obligations under a swap agreement
            will be accrued daily (offset against amounts owed to the Fund),
            and any accrued but unpaid net amounts owed to a swap counterparty
            will be covered by the segregation of assets determined to be liq-
            uid by the Adviser in accordance with procedures established by
            the Board of Trustees, to limit any potential leveraging of the
            Fund's portfolio. Obligations under swap agreements so covered
            will not be construed to be "senior securities" for purposes of
            the Fund's investment restriction concerning senior securities.
            The Fund will not enter into a swap agreement with any single
            party if the net amount owed or to be received under existing con-
            tracts with that party would exceed 5% of the Fund's assets.
               Whether the Fund's use of swap agreements will be successful in
            furthering its investment objective will depend on the Adviser's
            ability to predict correctly whether certain types of investments
            are likely to produce greater returns than other investments. Be-
            cause they are two-party contracts and because they may have terms
            of greater than seven days, swap agreements may be considered to
            be illiquid investments. Moreover, the Fund bears the risk of loss
            of the amount expected to be received under a swap agreement in
            the event of the default or bankruptcy of a swap agreement
            counterparty. The Fund will enter into swap agreements only with
            counterparties that meet certain standards for creditworthiness
            (generally, such counterparties would have to be eligible
            counterparties under the terms of the Fund's repurchase agreement
            guidelines). Certain restrictions imposed on the Fund by the In-
            ternal Revenue Code may limit the Fund's ability to use swap
            agreements. The swaps market is a relatively new market and is
            largely unregulated. It is possible that developments in the swaps
            market, including potential government regulation, could adversely
            affect the Fund's ability to terminate existing swap agreements or
            to realize amounts to be received under such agreements.
 
 
18
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            FUTURES CONTRACTS AND OPTIONS ON FUTURES CONTRACTS The Fund may
            invest in interest rate futures contracts and options thereon
            ("futures options"), and to the extent it may invest in foreign
            currency-denominated securities, may also invest in foreign cur-
            rency futures contracts and options thereon.
               There are several risks associated with the use of futures and
            futures options for hedging purposes. There can be no guarantee
            that there will be a correlation between price movements in the
            hedging vehicle and in the portfolio securities being hedged. An
            incorrect correlation could result in a loss on both the hedged
            securities in the Fund and the hedging vehicle, so that the port-
            folio return might have been greater had hedging not been attempt-
            ed. There can be no assurance that a liquid market will exist at a
            time when the Fund seeks to close out a futures contract or a
            futures option position. Most futures exchanges and boards of
            trade limit the amount of fluctuation permitted in futures con-
            tract prices during a single day; once the daily limit has been
            reached on a particular contract, no trades may be made that day
            at a price beyond that limit. In addition, certain of these in-
            struments are relatively new and without a significant trading
            history. As a result, there is no assurance that an active second-
            ary market will develop or continue to exist. Lack of a liquid
            market for any reason may prevent the Fund from liquidating an un-
            favorable position, and the Fund would remain obligated to meet
            margin requirements until the position is closed.
               The Fund may write covered straddles consisting of a call and a
            put written on the same underlying futures contract. A straddle
            will be covered when sufficient assets are deposited to meet the
            Fund's immediate obligations. The Fund may use the same liquid as-
            sets to cover both the call and put options where the exercise
            price of the call and put are the same, or the exercise price of
            the call is higher than that of the put. In such cases, the Fund
            will also segregate liquid assets equivalent to the amount, if
            any, by which the put is "in the money."
               The Fund will only enter into futures contracts or futures op-
            tions which are standardized and traded on a U.S. or foreign ex-
            change or board of trade, or similar entity, or quoted on an auto-
            mated quotation system. The Fund will use financial futures con-
            tracts and related options only for "bona fide hedging" purposes,
            as such term is defined in applicable regulations of the Commodity
            Futures Trading Commission ("CFTC") or, with respect to positions
            in financial futures and related options that do not qualify as
            "bona fide hedging" positions, will enter such positions only to
            the extent that aggregate initial margin deposits plus premiums
            paid by it for open futures option positions, less the amount by
            which any such positions are "in-the-money," would not exceed 5%
            of the Fund's net assets.
 
 
HYBRID      A hybrid instrument can combine the characteristics of securities,
INSTRUMENTS futures, and options. For example, the principal amount or inter-
            est rate of a hybrid could be tied (positively or negatively) to
            the price of some commodity, currency or securities index or an-
            other interest rate (each a "benchmark"). The interest rate or
            (unlike most fixed income securities) the principal amount payable
            at maturity of a hybrid security may be increased or decreased,
            depending on changes in the value of the benchmark.
               Hybrids can be used as an efficient means of pursuing a variety
            of investment goals, including currency hedging, duration manage-
            ment, and increased total return. Hybrids may not bear interest or
            pay dividends. The value of a hybrid or its interest rate may be a
            multiple of a benchmark and, as a result, may be leveraged and
            move (up or down) more steeply and rapidly than the benchmark.
            These benchmarks may be sensitive to economic and political
            events, such as commodity shortages and currency devaluations,
            which cannot be readily foreseen by the purchaser of a hybrid. Un-
            der certain conditions, the redemption value of a hybrid could be
            zero. Thus, an investment in a hybrid may entail significant mar-
            ket risks that are not associated with a similar investment in a
            traditional, U.S. dollar-denominated bond that has a fixed princi-
            pal amount and pays a fixed rate or floating rate of interest. The
            purchase of hybrids also exposes the Fund to the credit risk of
            the issuer of the hybrids. These risks may cause significant fluc-
            tuations in the net asset value of the Fund. Accordingly, the Fund
            will invest no more than 5% of its assets in hybrid instruments.
               Certain issuers of structured products such as hybrid instru-
            ments may be deemed to be investment companies as defined in the
            Investment Company Act of 1940 (the "1940 Act"). As a result, the
            Fund's investments in these products will be subject to limits ap-
            plicable to investments in investment companies and may be subject
            to restrictions contained in the 1940 Act.
 
                                                                             19
                                                                    Prospectus
<PAGE>
 
CATASTROPHE The Fund may invest in "catastrophe bonds." Catastrophe bonds are
BONDS       fixed income securities, for which the return of principal and
            payment of interest is contingent on the non-occurrence of a spe-
            cific "trigger" catastrophic event, such as a hurricane or an
            earthquake. They may be issued by government agencies, insurance
            companies, reinsurers, special purpose corporations or other on-
            shore or off-shore entities. If a trigger event causes losses ex-
            ceeding a specific amount in the geographic region and time period
            specified in a bond, a Fund investing in the bond may lose a por-
            tion or all of its principal invested in the bond. If no trigger
            event occurs, the Fund will recover its principal plus interest.
            For some catastrophe bonds, the trigger event or losses may be
            based on companywide losses, index-portfolio losses, industry in-
            dices, or readings of scientific instruments rather than specified
            actual losses. Often the catastrophe bonds provide for extensions
            of maturity that are mandatory, or optional at the discretion of
            the issuer, in order to process and audit loss claims in those
            cases where a trigger event has, or possibly has, occurred. In ad-
            dition to the specified trigger events, catastrophe bonds may also
            expose the Fund to certain unanticipated risks including but not
            limited to issuer (credit) default, adverse regulatory or juris-
            dictional interpretations, and adverse tax consequences.
               Catastrophe bonds are a relatively new type of financial in-
            strument. As such, there is no significant trading history of
            these securities, and there can be no assurance that a liquid mar-
            ket in these instruments will develop. See "Illiquid Securities"
            below. Lack of a liquid market may impose the risk of higher
            transaction costs and the possibility that a Fund may be forced to
            liquidate positions when it would not be advantageous to do so.
            Catastrophe bonds are typically rated, and the Fund will only in-
            vest in catastrophe bonds that meet the credit quality require-
            ments for the Fund.
 
 
INVESTMENT  The Fund may invest up to 10% of its assets in securities of other
IN          investment companies, such as closed-end management investment
INVESTMENT  companies, or in pooled accounts or other investment vehicles. As
COMPANIES   a shareholder of an investment company, the Fund may indirectly
            bear service and other fees which are in addition to the fees the
            Fund pays its service providers.
 
 
PORTFOLIO   The length of time the Fund has held a particular security is not
TURNOVER    generally a consideration in investment decisions. The investment
            policies of the Fund may lead to frequent changes in the Fund's
            investments, particularly in periods of volatile market movements.
            A change in the securities held by the Fund is known as "portfolio
            turnover." High portfolio turnover (e.g., over 100%) involves cor-
            respondingly greater expenses to the Fund, including brokerage
            commissions or dealer mark-ups and other transaction costs on the
            sale of securities and reinvestments in other securities. Such
            sales may result in realization of taxable capital gains (includ-
            ing short-term capital gains which are generally taxed at ordinary
            income tax rates). See "Taxes." The portfolio turnover rate for
            the Fund is set forth under "Financial Highlights."
 
 
ILLIQUID    The Fund may invest up to 15% of its net assets in illiquid secu-
SECURITIES  rities. Certain illiquid securities may require pricing at fair
            value as determined in good faith under the supervision of the
            Board of Trustees. The Adviser may be subject to significant de-
            lays in disposing of illiquid securities, and transactions in il-
            liquid securities may entail registration expenses and other
            transaction costs that are higher than transactions in liquid se-
            curities. The term "illiquid securities" for this purpose means
            securities that cannot be disposed of within seven days in the or-
            dinary course of business at approximately the amount at which the
            Fund has valued the securities. Illiquid securities are considered
            to include, among other things, written over-the-counter options,
            securities or other liquid assets being used as cover for such op-
            tions, repurchase agreements with maturities in excess of seven
            days, certain loan participation interests, fixed time deposits
            which are not subject to prepayment or provide for withdrawal pen-
            alties upon prepayment (other than overnight deposits), securities
            that are subject to legal or contractual restrictions on resale
            (such as privately placed debt securities) and other securities
            whose disposition is restricted under the federal securities laws
            (other than securities issued pursuant to Rule 144A under the Se-
            curities Act of 1933 and certain commercial paper that Pacific In-
            vestment Management has determined to be liquid under procedures
            approved by the Board of Trustees).
 
20 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               Illiquid securities may include privately placed securities,
            which are sold directly to a small number of investors, usually
            institutions. Unlike public offerings, such securities are not
            registered under the federal securities laws. Although certain of
            these securities may be readily sold, for example, under Rule
            144A, others may be illiquid, and their sale may involve substan-
            tial delays and additional costs.
 
 
SERVICE     Many of the services provided to the Fund depend on the smooth
SYSTEMS--   functioning of computer systems. Many systems in use today cannot
YEAR 2000   distinguish between the year 1900 and the year 2000. Should any of
PROBLEM     the service systems fail to process information properly, that
            could have an adverse impact on the Fund's operations and services
            provided to the shareholders. The Adviser, Distributor, Share-
            holder Servicing and Transfer Agent, Custodian, and certain other
            service providers to the Fund have reported that each is working
            toward mitigating the risks associated with the so-called
            "year 2000 problem." However, there can be no assurance that the
            problem will be corrected in all respects and that the Fund's op-
            erations and services provided to shareholders will not be ad-
            versely effected, nor can there be any assurance that the year
            2000 problem will not have an adverse effect on the entities whose
            securities are held by the Funds or on domestic or global markets
            or economies, generally.
 
            Performance Information
 
            From time to time the Trust may make available certain information
            about the performance of the Class A shares of the Fund. Informa-
            tion about the Fund's performance is based on the Fund's record to
            a recent date and is not intended to indicate future performance.
            Performance information is compiled separately for each class of
            the Fund's shares in accordance with the formulas described below.
               From time to time, the yield and total return for each class of
            shares of the Fund may be included in advertisements or reports to
            shareholders or prospective investors. Quotations of yield for the
            Fund or class will be based on the investment income per share (as
            defined by the Securities and Exchange Commission) during a par-
            ticular 30-day (or one-month) period (including dividends and in-
            terest), less expenses accrued during the period ("net investment
            income"), and will be computed by dividing net investment income
            by the maximum public offering price per share on the last day of
            the period.
               The total return of Class A shares of the Fund may be included
            in advertisements or other written material. When the Fund's total
            return is advertised with respect to its Class A shares, it will
            be calculated for the past year, the past five years, and since
            the establishment of the Fund, as more fully described in the
            Statement of Additional Information. For periods prior to the ini-
            tial offering date of Class A shares, total return presentations
            for the class will be based on the historical performance of an
            older class of the Fund restated to reflect current sales charges
            (if any) of the newer class. The older class to be used is set
            forth in the Statement of Additional Information. For these pur-
            poses, the performance of the older class will also be restated to
            reflect any different operating expenses (such as different admin-
            istrative fees and/or 12b-1/servicing fee charges) associated with
            the newer class. Total return for each class is measured by com-
            paring the value of an investment in the Fund at the beginning of
            the relevant period (in the case of Class A shares, giving effect
            to the maximum initial sales charge generally applicable to Class
            A shares) to the redemption value of the investment in the Fund at
            the end of the period (assuming immediate reinvestment of any div-
            idends or capital gains distributions at net asset value and giv-
            ing effect to the deduction of the maximum CDSC which would be
            payable). Total return may be advertised using alternative methods
            that reflect all elements of return, but that may be adjusted to
            reflect the cumulative impact of alternative fee and expense
            structures, such as the currently effective advisory and adminis-
            trative fees for the Fund.
               Current distribution information may also be provided to the
            Trust's shareholders in shareholder reports or other shareholder
            communications, or in certain types of sales literature provided
            to prospective investors. Current distribution information for a
            particular class of the Fund will be based on distributions for a
            specified period (i.e., total dividends
                                                                    Prospectus
                                                                              21
<PAGE>
 
            from net investment income), divided by the relevant class net as-
            set value per share on the last day of the period and annualized.
            The rate of current distributions does not reflect deductions for
            unrealized losses from transactions in derivative instruments such
            as options and futures, which may reduce total return. Current
            distribution rates differ from standardized yield rates in that
            they represent what a class of the Fund has declared and paid to
            shareholders as of the end of a specified period rather than the
            Fund's actual net investment income for that period.
               Performance information for the Trust may also be compared to
            various unmanaged indexes, such as the Standard & Poor's 500 Com-
            posite Stock Price Index, the Lehman Brothers Aggregate Bond In-
            dex, the Lehman Brothers Mortgage-Backed Securities Index, the
            Merrill Lynch 1 to 3 Year Treasury Index, the Lehman Intermediate
            and 20+ Year Treasury Blend Index, the Lehman BB Intermediate Cor-
            porate Index, indexes prepared by Lipper Analytical Services, the
            J.P. Morgan Global Index, the J.P. Morgan Emerging Markets Bond
            Index Plus, the Salomon Brothers World Government Bond Index-10
            Non U.S.-Dollar Hedged and the J.P. Morgan Government Bond Index
            Non U.S.-Dollar Hedged, and other entities or organizations which
            track the performance of investment companies or investment advis-
            ers. Unmanaged indexes (i.e., other than Lipper) generally do not
            reflect deductions for administrative and management costs and ex-
            penses. The Adviser may also report to shareholders or to the pub-
            lic in advertisements concerning the performance of the Adviser as
            adviser to clients other than the Trust, and on the comparative
            performance or standing of the Adviser in relation to other money
            managers. Such comparative information may be compiled or provided
            by independent ratings services or by news organizations. Any per-
            formance information, whether related to the Fund or to the Advis-
            er, should be considered in light of the Fund's investment objec-
            tives and policies, characteristics and quality of the portfolio,
            and the market conditions during the time period indicated, and
            should not be considered to be representative of what may be
            achieved in the future. For a description of the methods used to
            determine yield and total return for the Fund, see the Statement
            of Additional Information.
               Investment results of the Fund will fluctuate over time, and
            any presentation of the Fund's total return or yield for any prior
            period should not be considered as a representation of what an in-
            vestor's total return or yield may be in any future period.
 
            How to Buy Shares
 
            Class A shares of the Fund of the Trust are continuously offered
            through the Trust's principal underwriter, PIMCO Funds Distribu-
            tors LLC (the "Distributor"). Class A shares of the Fund are
            available as an investment option in retirement or savings plans.
            The administrator of such a plan or a prospective participant's
            employee benefits office can provide detailed information on how
            to participate in such a plan and how to elect the Fund as an in-
            vestment option. The terms of a plan may restrict the frequency or
            timing of a participant's contributions, allocations or redemp-
            tions, which may have the effect of limiting a participant's abil-
            ity to respond to changing markets conditions.
               A participant may be permitted to elect different investment
            options, alter the amounts contributed to the participant's plan,
            or change how contributions are allocated among investment options
            in accordance with the plan's specific provisions. A participant
            should consult the plan administrator or the participant's em-
            ployee benefits office for more details.
               Questions about the Fund should be directed to the Distributor
            at 1-800-426-0107. Questions about a participant's plan account
            should be directed to the plan administrator or the organization
            that provides recordkeeping services for the plan.
               All contributions received by the Distributor prior to the
            close of regular trading (normally 4:00 p.m., Eastern time) on the
            New York Stock Exchange (the "Exchange"), on a regular business
            day, are processed at that day's offering price, which will be net
            asset value next determined after acceptance of a contribution.
            However, contributions received by the Distributor after the of-
            fering price is determined that day will receive such offering
            price if the contributions were received by the plan administrator
            prior to such determination and were transmitted to and received
            by the Distributor
 
22
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            when trading on the Exchange is restricted or during an emergency
            which makes it impracticable for the Fund to dispose of its secu-
            rities or to determine fairly the value of its net assets, or dur-
            ing any other period as permitted by the Securities and Exchange
            Commission for the protection of investors. No share certificates
            will be issued.
 
            SALES AT NET ASSET VALUE The Fund may sell its Class A shares at
            net asset value without a sales charge to, among others, (a)
            trustees or other fiduciaries purchasing shares for certain em-
            ployer sponsored plans that have at least 100 eligible partici-
            pants or at least $1 million in total plan assets, and (b) trust-
            ees or other fiduciaries purchasing shares for certain employer-
            sponsored plans, the trustee, administrator, fiduciary, broker,
            trust company or registered investment adviser for which has an
            agreement with the Distributor with respect to such purchases. The
            Distributor will pay a commission to dealers who sell Class A
            shares of the Fund at net asset value to certain employer-spon-
            sored plans according to the following schedule: .50% of the first
            $2,000,000 and .25% of amounts over $2,000,000. From time to time,
            the Distributor, its parent and/or its affiliates may make addi-
            tional payments to one or more participating brokers based upon
            factors such as the level of sales or the length of time clients'
            assets have remained in the Trust.
 
            Exchange Privilege
 
            A participant's plan may allow exchanges from one investment op-
            tion to another. A participant should check with the plan adminis-
            trator for details on the rules governing exchanges in the plan,
            including the frequency of permitted exchanges. Certain investment
            options may be subject to unique restrictions. Exchanges are ac-
            cepted by the Trust only as permitted by a participant's plan.
 
            How to Redeem
 
            Shares are redeemed at their net asset value next determined after
            a proper redemption request has been received. There is no charge
            by the Distributor with respect to a redemption. Requests for re-
            demption received during a day by the Distributor prior to the ac-
            tual close of that day's regular trading on the Exchange (normal-
            ly, 4:00 p.m. Eastern time) will be confirmed at the net asset
            value effective as of the closing of the Exchange on that day.
 
            Distributor and Distribution and Servicing Plan
 
            The Distributor, a wholly owned subsidiary of PIMCO Advisors L.P.,
            is the principal underwriter of the Fund's shares and in that con-
            nection makes servicing payments to participating brokers, certain
            banks and other financial intermediaries in connection with the
            sale of Class A shares. Pursuant to a Distribution Contract with
            the Trust, with respect to the Fund's Class A shares, the Distrib-
            utor bears various other promotional and sales related expenses,
            including the cost of printing and mailing prospectuses to persons
            other than current shareholders. The Distributor, located at 2187
            Atlantic Street, Stamford, Connecticut 06902 is a broker-dealer
            registered with the Securities and Exchange Commission.
 
            CLASS A SERVICING FEES As compensation for services rendered and
            expenses borne by the Distributor in connection with personal
            services rendered to Class A shareholders of the Fund and the
            maintenance of Class A shareholder accounts, the Trust pays the
            Distributor servicing fees up to the annual rate of .25% of the
            Fund's average daily net assets attributable to Class A shares.
 
                                                                             23
                                                                    Prospectus
<PAGE>
 
            prior to 10:00 a.m. Eastern time on the next business day. Contri-
            butions received on other than a regular business day will be exe-
            cuted on the next succeeding regular business day. The Distribu-
            tor, in its sole discretion, may accept or reject any order for
            purchase of Fund shares. The sale of shares will be suspended dur-
            ing any period in which the Exchange is closed for other than
            weekends or holidays, or if permitted by the rules of the Securi-
            ties and Exchange Commission, The Class A servicing fees paid to
            the Distributor are paid under a Distribution and Servicing Plan
            adopted pursuant to Rule 12b-l under the 1940 Act, and is of the
            type known as a "compensation" plan. This means that, although the
            Trustees of the Trust are expected to take into account the ex-
            penses of the Distributor and its predecessors in their periodic
            review of the Distribution and Servicing Plan, the fees are pay-
            able to compensate the Distributor for services rendered even if
            the amount paid exceeds the Distributor's expenses.
               The servicing fee applicable to Class A shares of the Fund may
            be spent by the Distributor on personal services rendered to
            shareholders of the Fund and the maintenance of shareholder ac-
            counts, including compensation to, and expenses (including tele-
            phone and overhead expenses) of, financial consultants or other
            employees of participating or introducing brokers, certain banks
            and other financial intermediaries who aid in the processing of
            purchase or redemption requests or the processing of dividend pay-
            ments, who provide information periodically to shareholders show-
            ing their positions in the Fund's shares, who forward communica-
            tions from the Trust to shareholders, who render ongoing advice
            concerning the suitability of particular investment opportunities
            offered by the Trust in light of the shareholders' needs, who re-
            spond to inquiries from shareholders relating to such services, or
            who train personnel in the provision of such services. Distribu-
            tion and servicing fees may also be spent on interest relating to
            unreimbursed distribution or servicing expenses from prior years.
               Many of the Distributor's servicing efforts involve the Trust
            as a whole, so that fees paid by Class A shares of the Fund may
            indirectly support servicing efforts relating to shares of the
            same class of the other series of the Trust. In reporting its ex-
            penses to the Trustees, the Distributor itemizes expenses that re-
            late to the distribution and/or servicing of the Fund's shares,
            and allocates other expenses among all of the operational series
            based on their relative net assets. Expenses allocated to the Fund
            are further allocated among its classes of shares annually based
            on the relative sales of each class, except for any expenses that
            relate only to the sale or servicing of a single class. The Dis-
            tributor may make payments to brokers (and with respect to servic-
            ing fees only, to certain banks and other financial intermediar-
            ies) of up to .25% annually of the average daily net assets at-
            tributable to shares in the accounts of their customers or cli-
            ents. Payments may be made, in part, with respect to Class A
            shares of the Fund issued to former shareholders of PIMCO Advisors
            Funds in connection with the reorganizations of series of PIMCO
            Advisors Funds with series of the Trust, including the Fund, in a
            transaction which took place on January 17, 1997.
               The Distributor may from time to time pay additional cash bo-
            nuses or other incentives to selected participating brokers in
            connection with the servicing of Class A shares of the Fund. On
            some occasions, such bonuses or incentives may be conditioned upon
            the sale of a specified minimum dollar amount of the shares of the
            Fund and/or all of the series of the Trust together or a particu-
            lar class of shares, during a specific period of time. The Dis-
            tributor currently expects that such additional bonuses or incen-
            tives will not exceed .50% of the amount of any sale. Pacific In-
            vestment Management (in its capacity as administrator) may also
            pay participating brokers and other intermediaries for transfer
            agency and other services.
               If in any year the Distributor's expenses incurred in connec-
            tion with the servicing of shareholders and the maintenance of
            shareholder accounts exceed the servicing fees paid by the Trust,
            the Distributor would recover such excess only if the Distribution
            and Servicing Plan with respect to Class A shares continues to be
            in effect in some later year when the servicing fees exceed the
            Distributor's expenses. The Trust is not obligated to repay any
            unreimbursed expenses that may exist at such time, if any, as the
            relevant Distribution and Servicing Plan terminates.
 
 
24
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            How Net Asset Value Is Determined
 
            The net asset value of Class A shares of the Fund will be deter-
            mined once on each day on which the Exchange is open as of the
            close of regular trading on the Exchange (normally 4:00 p.m.,
            Eastern time). Net asset value will not be determined on days on
            which the Exchange is closed.
               Portfolio securities and other assets for which market quota-
            tions are readily available are stated at market value. Market
            value is determined on the basis of last reported sales prices, or
            if no sales are reported, as is the case for most securities
            traded over-the-counter, at the mean between representative bid
            and asked quotations obtained from a quotation reporting system or
            from established market makers. Fixed income securities, including
            those to be purchased under firm commitment agreements (other than
            obligations having a maturity of 60 days or less), are normally
            valued on the basis of quotations obtained from brokers and deal-
            ers or pricing services, which take into account appropriate fac-
            tors such as institutional-sized trading in similar groups of se-
            curities, yield, quality, coupon rate, maturity, type of issue,
            trading characteristics, and other market data.
               Quotations of foreign securities in foreign currency are con-
            verted to U.S. dollar equivalents using foreign exchange quota-
            tions received from independent dealers. Short-term investments
            having a maturity of 60 days or less are valued at amortized cost,
            when the Board of Trustees determines that amortized cost is their
            fair value. Certain fixed income securities for which daily market
            quotations are not readily available may be valued, pursuant to
            guidelines established by the Board of Trustees, with reference to
            fixed income securities whose prices are more readily obtainable
            and whose durations are comparable to the securities being valued.
            Subject to the foregoing, other securities for which market quota-
            tions are not readily available are valued at fair value as deter-
            mined in good faith by the Board of Trustees.
               The Fund's liabilities are allocated among its classes. The to-
            tal of such liabilities allocated to a class plus that class's
            distribution and/or servicing fees and any other expenses spe-
            cially allocated to that class are then deducted from the class's
            proportionate interest in the Fund's assets, and the resulting
            amount for each class is divided by the number of shares of that
            class outstanding to produce the class's "net asset value" per
            share.
 
            Distributions
 
            The Fund pays out as dividends substantially all of its net in-
            vestment income (which comes from dividends and interest it re-
            ceives or is deemed to receive from its investments) and net real-
            ized short-term capital gains. For these purposes and for federal
            income tax purposes, a portion of the premiums from certain ex-
            pired call or put options written by the Fund, net gains from
            closing purchase and sale transactions with respect to such op-
            tions, and net gains from futures transactions are treated as
            short-term capital gains. The Fund distributes substantially all
            of its net realized capital gains, if any, after giving effect to
            any available capital loss carry-over.
               Shares begin earning dividends on the effective date of pur-
            chase, which is the date that funds are received by the Trust for
            the purchase of shares. Dividends are declared daily from net in-
            vestment income to shareholders of record at the close of the pre-
            vious business day, and distributed to shareholders monthly. Any
            net realized capital gains from the sale of portfolio securities
            will be distributed no less frequently than once yearly. Dividend
            and capital gain distributions of the Fund will be reinvested in
            additional shares of the Fund unless the shareholder elects to
            have them paid in cash.
               Dividends and capital gains distributions may be declared more
            or less frequently in the discretion of the Trustees. There are no
            sales charges on reinvested dividends.
 
                                                                    Prospectus
                                                                              25
<PAGE>
 
            Taxes
 
            The Fund intends to qualify as a regulated investment company an-
            nually and to elect to be treated as a regulated investment com-
            pany under the Internal Revenue Code of 1986, as amended. As such,
            the Fund generally will not pay federal income tax on the income
            and gains it pays as dividends to its shareholders. In order to
            avoid a 4% federal excise tax, the Fund intends to distribute each
            year substantially all of its net income and gains.
               Distributions received by tax-exempt shareholders will not be
            subject to federal income tax to the extent permitted under appli-
            cable tax law. To the extent that a shareholder is not exempt from
            tax on Fund distributions, such shareholder will be subject to tax
            on dividends received from the Fund, regardless of whether re-
            ceived in cash or reinvested in additional shares. All sharehold-
            ers must treat dividends, other than capital gain dividends or
            dividends that represent a return of capital to shareholders, as
            ordinary income.
               Dividends designated by the Fund as capital gain dividends
            derived from the Fund's net capital gain (that is, the excess of
            net long-term gain over net short-term loss) are taxable to
            shareholders as long-term capital gain except as provided by an
            applicable tax exemption. Any distributions that are not from the
            Fund's net investment income, short-term capital gain, or net
            capital gain may be characterized as a return of capital to
            shareholders or, in some cases, as capital gain. Certain dividends
            declared in October, November or December of a calendar year are
            taxable to shareholders (who are subject to tax on dividends) as
            though received on December 31 of that year if paid to
            shareholders during January of the following calendar year. The
            Fund will advise shareholders annually of the amount and nature of
            the dividends paid to them.
               Interest accrued by the Fund from inflation-indexed bonds will
            be includable in the Fund's gross income in the period in which it
            accrues. Periodic adjustments for inflation in the principal value
            of these securities also may give rise to original issue discount,
            which, likewise, will be includable in the Fund's gross income on
            a current basis, regardless of whether the Fund receives any cash
            payments. See "Taxation--Original Issue Discount" in the Statement
            of Additional Information. Amounts includable in the Fund's gross
            income become subject to tax-related distribution requirements.
            Accordingly, the Fund may be required to make annual distributions
            to shareholders in excess of the cash received in a given period
            from these investments. As a result, the Fund may be required to
            liquidate certain investments at a time when it is not advanta-
            geous to do so. If the principal value of an inflation-indexed
            bond is adjusted downward in any period as a result of deflation,
            the reduction may be treated as a loss to the extent the reduction
            exceeds coupon payments received in that period; in that case, the
            amount distributable by the Fund may be reduced and amounts dis-
            tributed previously in the taxable year may be characterized in
            some circumstances as a return of capital.
               Taxable shareholders should note that the timing of their in-
            vestment could have undesirable tax consequences. Dividends and
            distributions on a Fund's shares are generally subject to federal
            income tax as described herein to the extent they do not exceed
            the Fund's realized income and gains, even though such dividends
            and distributions may economically represent a return of a partic-
            ular shareholder's investment. Such distributions are likely to
            occur in respect of shares purchased at a time when the Fund's net
            asset value reflects gains that are either unrealized or realized
            but not distributed. Such realized gains may be required to be
            distributed even when a Fund's net asset value also reflects
            unrealized losses.
               If the Fund is used as an investment option in an employer-
            sponsored retirement savings plan, dividend and capital gains
            distributions from the Fund generally will not be subject to
            current taxation, but will accumulate on a tax-deferred basis. In
            general, employer-sponsored retirement and savings plans are
            governed by a complex set of tax rules. Participants in such a
            plan should consult the plan administrator, the plan's Summary
            Plan Description, or a professional tax adviser regarding the tax
            consequences of participation in the plan and of any plan
            contributions or withdrawals.
               The preceding discussion relates only to federal income tax;
            the consequences under other tax laws may differ. For additional
            information relating to the tax aspects of investing in the Fund,
            see the Statement of Additional Information.
 
26 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
 
            Management of the Trust
 
            The business affairs of the Trust are managed under the direction
            of the Board of Trustees. The Trustees are Guilford C. Babcock, R.
            Wesley Burns, Vern O. Curtis, Brent R. Harris, Thomas P. Kemp, and
            William J. Popejoy. Additional information about the Trustees and
            the Trust's executive officers may be found in the Statement of
            Additional Information under the heading "Management--Trustees and
            Officers."
 
 
INVESTMENT  Pacific Investment Management serves as investment adviser ("Ad-
ADVISER     viser") to the Fund pursuant to an investment advisory contract.
            The Adviser is an investment management company founded in 1971,
            and had approximately $148 billion in assets under management as
            of September 30, 1998.
               Pacific Investment Management is a subsidiary of PIMCO Advisors
            L.P. ("PIMCO Advisors"). The general partners of PIMCO Advisors
            are PIMCO Partners, G.P. and PIMCO Advisors Holdings L.P. PIMCO
            Partners, G.P. is a general partnership between PIMCO Holding LLC,
            a Delaware limited liability company and an indirect wholly-owned
            subsidiary of Pacific Life Insurance Company, and PIMCO Partners
            LLC, a California limited liability company controlled by the cur-
            rent Managing Directors and two former Managing Directors of Pa-
            cific Investment Management. PIMCO Partners, G.P. is the sole gen-
            eral partner of PIMCO Advisors Holdings L.P. Pacific Investment
            Management's address is 840 Newport Center Drive, Suite 300, New-
            port Beach, California 92660. Pacific Investment Management is
            registered as an investment adviser with the Securities and Ex-
            change Commission and as a commodity trading advisor with the
            CFTC.
               The Adviser manages the investment and reinvestment of the as-
            sets of the Fund. The Adviser is responsible for placing orders
            for the purchase and sale of the Fund's investments directly with
            brokers or dealers selected by it in its discretion. See "Portfo-
            lio Transactions" in the Statement of Additional Information.
               The portfolio manager responsible for management of the Fund is
            William H. Gross, Managing Director, Pacific Investment Manage-
            ment. A Fixed Income Portfolio Manager, Mr. Gross is one of the
            founders of Pacific Investment Management and has managed the Fund
            since its inception, May 11, 1987.
 
 
FUND        Pacific Investment Management also serves as administrator for the
ADMINI-     Fund's Class A shares pursuant to an administration agreement with
STRATOR     the Trust. Pacific Investment Management provides administrative
            services for Class A shareholders of the Fund, which include cler-
            ical help and accounting, bookkeeping, internal audit services,
            and certain other services required by the Fund, preparation of
            reports to the Fund's shareholders and regulatory filings. Pacific
            Investment Management may also retain certain of its affiliates to
            provide certain of these services. In addition, Pacific Investment
            Management, at its own expense, arranges for the provision of le-
            gal, audit, custody, transfer agency (including sub-transfer
            agency and other administrative services) and other services for
            the Fund, and is responsible for the costs of registration of the
            Fund's shares and the printing of prospectuses and shareholder re-
            ports for current shareholders.
               The Fund (and not Pacific Investment Management) is responsible
            for the following expenses: (i) salaries and other compensation of
            any of the Trust's executive officers and employees who are not
            officers, directors, stockholders or employees of Pacific Invest-
            ment Management or its subsidiaries or affiliates; (ii) taxes and
            governmental fees; (iii) brokerage fees and commissions and other
            portfolio transaction expenses; (iv) the costs of borrowing money,
            including interest expenses; (v) fees and expenses of the Trustees
            who are not "interested persons" of Pacific Investment Management
            or the Trust, and any counsel retained exclusively for their bene-
            fit; (vi) extraordinary expenses, including costs of litigation
            and indemnification expenses; (vii) expenses, such as organiza-
            tional expenses, which are capitalized in accordance with gener-
            ally accepted accounting principles; and (viii) any expenses allo-
            cated or allocable to a specific class of shares, which include
            servicing fees payable with respect to Class A shares, and may in-
            clude certain other expenses as permitted by the Trust's Multi-
            Class Plan adopted pursuant to Rule 18f-3 under the 1940 Act, sub-
            ject to review and approval by the Trustees.
                                                                    Prospectus
                                                                              27
<PAGE>
 
ADVISORY    The Fund features fixed advisory and administrative fee rates. For
AND         providing investment advisory and administrative services to the
ADMINIS-    Fund as described above, Pacific Investment Management receives
TRATIVE     monthly fees from the Fund at an annual rate (i) based on the av-
FEES        erage daily net assets of the Fund for advisory fees and, (ii) at-
            tributable in the aggregate to the Fund's Class A, Class B and
            Class C shares for administrative fees, as follows:
 
 
<TABLE>
<CAPTION>
           ADVISORY    ADMINISTRATIVE
           FEE RATE    FEE RATE
           --------------------------
           <S>         <C>
           .25%        .40%
</TABLE>
 
 
               Both the investment advisory contract and administration agree-
            ment with respect to Class A shares of the Fund may be terminated
            by the Trustees at any time on 60 days' written notice. The in-
            vestment advisory contract may be terminated by Pacific Investment
            Management on 60 days' written notice. Following the expiration of
            the one-year period commencing with the effectiveness of the ad-
            ministration agreement, it may be terminated by Pacific Investment
            Management on 60 days' written notice. Following its initial two-
            year term, the investment advisory contract will continue from
            year to year if approved by the Trustees. Following its initial
            one-year term, the administration agreement with respect to Class
            A shares of the Fund will continue from year-to-year if approved
            by the Trustees.
 
PORTFOLIO   Pursuant to the advisory contract, the Adviser places orders for
TRANS-      the purchase and sale of portfolio investments for the Fund's ac-
ACTIONS     counts with brokers or dealers selected by it in its discretion.
            In effecting purchases and sales of portfolio securities for the
            account of the Fund, the Adviser will seek the best price and exe-
            cution of the Fund's orders. In doing so, the Fund may pay higher
            commission rates than the lowest available when the Adviser be-
            lieves it is reasonable to do so in light of the value of the bro-
            kerage and research services provided by the broker effecting the
            transaction. The Adviser also may consider sales of shares of the
            Trust as a factor in the selection of broker-dealers to execute
            portfolio transactions for the Fund.
               The Adviser manages the Fund without regard generally to re-
            strictions on portfolio turnover, except those imposed on its
            ability to engage in short-term trading by provisions of the fed-
            eral tax laws. The use of certain derivative instruments with rel-
            atively short maturities may tend to exaggerate the portfolio
            turnover rate for the Fund. Trading in fixed income securities
            does not generally involve the payment of brokerage commissions,
            but does involve indirect transaction costs. The use of futures
            contracts may involve the payment of commissions to futures com-
            mission merchants. The higher the rate of portfolio turnover of
            the Fund, the higher all these transaction costs borne by the Fund
            generally will be. The portfolio turnover rate for the Fund is set
            forth under "Financial Highlights."
               Some securities considered for investments by the Fund may also
            be appropriate for other clients served by the Adviser. If a pur-
            chase or sale of securities consistent with the investment poli-
            cies of the Fund and one or more of these clients served by the
            Adviser is considered at or about the same time, transactions in
            such securities will be allocated among the Fund and clients in a
            manner deemed fair and reasonable by the Adviser.
 
            Description of the Trust
 

CAPITAL-    The Trust was organized as a Massachusetts business trust on Feb-
IZATION     ruary 19, 1987. The Board of Trustees may establish additional
            portfolios in the future. The capitalization of the Trust consists
            solely of an unlimited number of shares of beneficial interest
            with a par value of $0.0001 each. When issued, shares of the Trust
            are fully paid, non-assessable and freely transferable.
               Under Massachusetts law, shareholders could, under certain cir-
            cumstances, be held personally liable for the obligations of the
            Trust. However, the Declaration of Trust disclaims liability of
            the shareholders, Trustees or officers of the Trust for acts or
            obligations of the Trust, which are binding only on the assets and
            property of the Trust, and requires that notice of the disclaimer
            be given in each contract or obligation entered into or executed
            by the Trust or the
 
28 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Trustees. The Declaration of Trust also provides for indemnifica-
            tion out of Trust property for all loss and expense of any share-
            holder held personally liable for the obligations of the Trust.
            The risk of a shareholder incurring financial loss on account of
            shareholder liability is limited to circumstances in which such
            disclaimer is inoperative or the Trust itself is unable to meet
            its obligations, and thus should be considered remote.
 
 
MULTIPLE    In addition to Class A shares, the Fund offers Class B, Class C,
CLASSES OF  Class D, Institutional Class and Administrative Class shares,
SHARES      through separate propectuses. Class A shares sold for personal in-
            vestment and the other classes of the Fund may have different
            sales charges and expense levels, which will affect performance
            accordingly. This Prospectus relates only to the Class A shares of
            the Fund. To obtain more information about the other classes,
            please call the Distributor at 800-927-4648 (for Institutional and
            Administrative Classes), 800-426-0107 (for Class B and C), or 888-
            87-PIMCO (for Class D).
 
VOTING      Shareholders have the right to vote on the election of Trustees
            and on any and all matters on which the law or the Declaration of
            Trust states they may be entitled to vote. The Trust is not re-
            quired to hold regular annual meetings of Trust shareholders and
            does not intend to do so. Shareholders of Class A shares or the
            Fund have separate voting rights with respect to matters that only
            affect that class or the Fund. See "Other Information--Voting
            Rights" in the Statement of Additional Information.
               The Declaration of Trust provides that the holders of not less
            than two-thirds of the outstanding shares of the Trust may remove
            a person serving as Trustee either by declaration in writing or at
            a meeting called for such purpose. The Trustees are required to
            call a meeting for the purpose of considering the removal of a
            person serving as Trustee if requested in writing to do so by the
            holders of not less than 10% of the outstanding shares of the
            Trust. Shares entitle their holders to one vote per share (with
            proportionate voting for fractional shares).
 
            Mailings to Shareholders
 
            To reduce the volume of mail shareholders receive, it is antici-
            pated that only one copy of most Trust reports, such as the
            Trust's annual report, will be mailed to a shareholder's household
            (same surname, same address). A shareholder may call 1-800-426-
            0107 if additional shareholder reports are desired.
                                                                    Prospectus
                                                                              29
<PAGE>
 
            Appendix A
            Description of Duration
 
            Duration is a measure of the expected life of a fixed income secu-
            rity that was developed as a more precise alternative to the con-
            cept of "term to maturity." Traditionally, a fixed income
            security's "term to maturity" has been used as a proxy for the
            sensitivity of the security's price to changes in interest rates
            (which is the "interest rate risk" or "volatility" of the securi-
            ty). However, "term to maturity" measures only the time until a
            fixed income security provides its final payment, taking no ac-
            count of the pattern of the security's payments prior to maturity.
            In contrast, duration incorporates a bond's yield, coupon interest
            payments, final maturity and call features into one measure. Dura-
            tion management is one of the fundamental tools used by the Advis-
            er.
               Duration is a measure of the expected life of a fixed income
            security on a present value basis. Duration takes the length of
            the time intervals between the present time and the time that the
            interest and principal payments are scheduled or, in the case of a
            callable bond, expected to be received, and weights them by the
            present values of the cash to be received at each future point in
            time. For any fixed income security with interest payments occur-
            ring prior to the payment of principal, duration is always less
            than maturity. In general, all other things being equal, the lower
            the stated or coupon rate of interest of a fixed income security,
            the longer the duration of the security; conversely, the higher
            the stated or coupon rate of interest of a fixed income security,
            the shorter the duration of the security.
               Futures, options and options on futures have durations which,
            in general, are closely related to the duration of the securities
            which underlie them. Holding long futures or call option positions
            (backed by a segregated account of cash and cash equivalents) will
            lengthen the Fund's duration by approximately the same amount that
            holding an equivalent amount of the underlying securities would.
               Short futures or put option positions have durations roughly
            equal to the negative duration of the securities that underlie
            these positions, and have the effect of reducing portfolio dura-
            tion by approximately the same amount that selling an equivalent
            amount of the underlying securities would.
               There are some situations where even the standard duration cal-
            culation does not properly reflect the interest rate exposure of a
            security. For example, floating and variable rate securities often
            have final maturities of ten or more years; however, their inter-
            est rate exposure corresponds to the frequency of the coupon re-
            set. For inflation-indexed bonds, duration is calculated on the
            basis of modified real duration, which measures price changes of
            inflation-indexed bonds on the basis of changes in real, rather
            than nominal, interest rates. Another example where the interest
            rate exposure is not properly captured by duration is the case of
            mortgage pass-through securities. The stated final maturity of
            such securities is generally 30 years, but current prepayment
            rates are more critical in determining the securities' interest
            rate exposure. Finally, the duration of a fixed income security
            may vary over time in response to changes in interest rates and
            other market factors. In these and other similar situations, the
            Adviser will use more sophisticated analytical techniques that in-
            corporate the anticipated economic life of a security into the de-
            termination of its interest rate exposure.
 
30
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
            Appendix B
            Description of Securities Ratings
 
            The Fund's investments may range in quality from securities rated
            in the lowest category in which the Fund is permitted to invest to
            securities rated in the highest category (as rated by Moody's or
            S&P or, if unrated, determined by the Adviser to be of comparable
            quality). The percentage of the Fund's assets invested in securi-
            ties in a particular rating category will vary. Following is a de-
            scription of Moody's and S&P's ratings applicable to fixed income
            securities.
 
 
MOODY'S     CORPORATE AND MUNICIPAL BOND RATINGS
INVESTORS      Aaa: Bonds which are rated Aaa are judged to be of the best
SERVICE,    quality. They carry the smallest degree of investment risk and are
INC.        generally referred to as "gilt edge." Interest payments are pro-
            tected by a large or by an exceptionally stable margin and princi-
            pal is secure. While the various protective elements are likely to
            change, such changes as can be visualized are most unlikely to im-
            pair the fundamentally strong position of such issues.
               Aa: Bonds which are rated Aa are judged to be of high quality
            by all standards. Together with the Aaa group they comprise what
            are generally known as high-grade bonds. They are rated lower than
            the best bonds because margins of protection may not be as large
            as in Aaa securities or fluctuation of protective elements may be
            of greater amplitude or there may be other elements present that
            make the long-term risks appear somewhat larger than with Aaa se-
            curities.
               A: Bonds which are rated A possess many favorable investment
            attributes and are to be considered as upper-medium-grade obliga-
            tions. Factors giving security to principal and interest are con-
            sidered adequate but elements may be present that suggest a sus-
            ceptibility to impairment sometime in the future.
               Baa: Bonds which are rated Baa are considered as medium-grade
            obligations (i.e., they are neither highly protected nor poorly
            secured). Interest payments and principal security appear adequate
            for the present but certain protective elements may be lacking or
            may be characteristically unreliable over any great length of
            time. Such bonds lack outstanding investment characteristics and
            in fact have speculative characteristics as well.
               Ba: Bonds which are rated Ba are judged to have speculative el-
            ements; their future cannot be considered as well-assured. Often
            the protection of interest and principal payments may be very mod-
            erate and thereby not well safeguarded during both good and bad
            times over the future. Uncertainty of position characterizes bonds
            in this class.
               B: Bonds which are rated B generally lack characteristics of a
            desirable investment. Assurance of interest and principal payments
            or of maintenance of other terms of the contract over any long pe-
            riod of time may be small.
               Caa: Bonds which are rated Caa are of poor standing. Such is-
            sues may be in default or there may be present elements of danger
            with respect to principal or interest.
               Ca: Bonds which are rated Ca represent obligations which are
            speculative in a high degree. Such issues are often in default or
            have other marked shortcomings.
               C: Bonds which are rated C are the lowest rated class of bonds
            and issues so rated can be regarded as having extremely poor pros-
            pects of ever attaining any real investment standing.
               Moody's applies numerical modifiers, 1, 2, and 3 in each ge-
            neric rating classified from Aa through B in its corporate bond
            rating system. The modifier 1 indicates that the security ranks in
            the higher end of its generic rating category; the modifier 2 in-
            dicates a mid-range ranking; and the modifier 3 indicates that the
            issue ranks in the lower end of its generic rating category.
 
            CORPORATE SHORT-TERM DEBT RATINGS
            Moody's short-term debt ratings are opinions of the ability of is-
            suers to repay punctually senior debt obligations which have an
            original maturity not exceeding one year. Obligations relying upon
            support mechanisms such as letters of credit and bonds of indem-
            nity are excluded unless explicitly rated.
 
                                                                             31
                                                                    Prospectus
<PAGE>
 
               Moody's employs the following three designations, all judged to
            be investment grade, to indicate the relative repayment ability of
            rated issuers:
               PRIME-1: Issuers rated Prime-1 (or supporting institutions)
            have a superior ability for repayment of senior short-term debt
            obligations. Prime-1 repayment ability will often be evidenced by
            many of the following characteristics: leading market positions in
            well-established industries; high rates of return on funds em-
            ployed; conservative capitalization structure with moderate reli-
            ance on debt and ample asset protection; broad margins in earnings
            coverage of fixed financial charges and high internal cash genera-
            tion; and well-established access to a range of financial markets
            and assured sources of alternate liquidity.
               PRIME-2: Issuers rated Prime-2 (or supporting institutions)
            have a strong ability for repayment of senior short-term debt ob-
            ligations. This will normally be evidenced by many of the charac-
            teristics cited above but to a lesser degree. Earnings trends and
            coverage ratios, while sound, may be more subject to variation.
            Capitalization characteristics, while still appropriate, may be
            more affected by external conditions. Ample alternate liquidity is
            maintained.
               PRIME-3: Issuers rated Prime-3 (or supporting institutions)
            have an acceptable ability for repayment of senior short-term ob-
            ligations. The effect of industry characteristics and market com-
            positions may be more pronounced. Variability in earnings and
            profitability may result in changes in the level of debt protec-
            tion measurements and may require relatively high financial lever-
            age. Adequate alternate liquidity is maintained.
               NOT PRIME: Issuers rated Not Prime do not fall within any of
            the Prime rating categories.
 
 
STANDARD &  CORPORATE AND MUNICIPAL BOND RATINGS
POOR'S
RATINGS     Investment Grade                                                   
SERVICES       AAA: Debt rated AAA has the highest rating assigned by S&P. Ca- 
            pacity to pay interest and repay principal is extremely strong.    
               AA: Debt rated AA has a very strong capacity to pay interest    
            and repay principal and differs from the highest rated issues only 
            in small degree.                                                   
               A: Debt rated A has a strong capacity to pay interest and repay 
            principal although it is somewhat more susceptible to the adverse  
            effects of changes in circumstances and economic conditions than   
            debt in higher rated categories.                                   
               BBB: Debt rated BBB is regarded as having an adequate capacity  
            to pay interest and repay principal. Whereas it normally exhibits  
            adequate protection parameters, adverse economic conditions, or    
            changing circumstances are more likely to lead to a weakened ca-   
            pacity to pay interest and repay principal for debt in this cate-  
            gory than in higher-rated categories.                               
            
            Speculative Grade
            Debt rated BB, B, CCC, CC, and C is regarded as having predomi-
            nantly speculative characteristics with respect to capacity to pay
            interest and repay principal. BB indicates the least degree of
            speculation and C the highest. While such debt will likely have
            some quality and protective characteristics, these are outweighed
            by large uncertainties or major exposures to adverse conditions.
               BB: Debt rated BB has less near-term vulnerability to default
            than other speculative issues. However, it faces major ongoing un-
            certainties or exposure to adverse business, financial, or eco-
            nomic conditions which could lead to inadequate capacity to meet
            timely interest and principal payments. The BB rating category is
            also used for debt subordinated to senior debt that is assigned an
            actual or implied BBB- rating.
               B: Debt rated B has a greater vulnerability to default but cur-
            rently has the capacity to meet interest payments and principal
            repayments. Adverse business, financial, or economic conditions
            will likely impair capacity or willingness to pay interest and re-
            pay principal. The B rating category is also used for debt subor-
            dinated to senior debt that is assigned an actual or implied BB or
            BB- rating.
 
32
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
               CCC: Debt rated CCC has a currently identifiable vulnerability
            to default and is dependent upon favorable business, financial,
            and economic conditions to meet timely payment of interest and re-
            payment of principal. In the event of adverse business, financial
            or economic conditions, it is not likely to have the capacity to
            pay interest and repay principal. The CCC rating category is also
            used for debt subordinated to senior debt that is assigned an ac-
            tual or implied B or B- rating.
               CC: The rating CC is typically applied to debt subordinated to
            senior debt that is assigned an actual or implied CCC rating.
               C: The rating C is typically applied to debt subordinated to
            senior debt that is assigned an actual or implied CCC- debt rat-
            ing. The C rating may be used to cover a situation where a bank-
            ruptcy petition has been filed, but debt service payments are con-
            tinued.
               CI: The rating CI is reserved for income bonds on which no in-
            terest is being paid.
               D: Debt rated D is in payment default. The D rating category is
            used when interest payments or principal payments are not made on
            the date due even if the applicable grace period has not expired,
            unless S&P believes that such payments will be made during such
            grace period. The D rating will also be used upon the filing of a
            bankruptcy petition if debt service payments are jeopardized.
               Plus (+) or Minus (-): The ratings from AA to CCC may be modi-
            fied by the addition of a plus or minus sign to show relative
            standing within the major rating categories.
               Provisional ratings: The letter "p" indicates that the rating
            is provisional. A provisional rating assumes the successful com-
            pletion of the project being financed by the debt being rated and
            indicates that payment of debt service requirements is largely or
            entirely dependent upon the successful and timely completion of
            the project. This rating, however, while addressing credit quality
            subsequent to completion of the project, makes no comment on the
            likelihood of, or the risk of default upon failure of, such com-
            pletion. The investor should exercise his own judgment with re-
            spect to such likelihood and risk.
               r: The "r" is attached to highlight derivative, hybrid, and
            certain other obligations that S&P believes may experience high
            volatility or high variability in expected returns due to non-
            credit risks. Examples of such obligations are: securities whose
            principal or interest return is indexed to equities, commodities,
            or currencies; certain swaps and options; and interest only and
            principal only mortgage securities.
               The absence of an "r" symbol should not be taken as an indica-
            tion that an obligation will exhibit no volatility or variability
            in total return.
               N.R.: Not rated.
               Debt obligations of issuers outside the United States and its
            territories are rated on the same basis as domestic corporate and
            municipal issues. The ratings measure the creditworthiness of the
            obligor but do not take into account currency exchange and related
            uncertainties.
 
            COMMERCIAL PAPER RATING DEFINITIONS
            An S&P commercial paper rating is a current assessment of the
            likelihood of timely payment of debt having an original maturity
            of no more than 365 days. Ratings are graded into several catego-
            ries, ranging from A for the highest quality obligations to D for
            the lowest. These categories are as follows:
               A-1: This highest category indicates that the degree of safety
            regarding timely payment is strong. Those issues determined to
            possess extremely strong safety characteristics are denoted with a
            plus sign (+) designation.
               A-2: Capacity for timely payment on issues with this designa-
            tion is satisfactory. However, the relative degree of safety is
            not as high as for issues designated A-1.
               A-3: Issues carrying this designation have adequate capacity
            for timely payment. They are, however, more vulnerable to the ad-
            verse effects of changes in circumstances than obligations carry-
            ing the higher designations.
               B: Issues rated B are regarded as having only speculative ca-
            pacity for timely payment.
               C: This rating is assigned to short-term debt obligations with
            a doubtful capacity for payment.
 
                                                                             33
                                                                    Prospectus
<PAGE>
 
               D: Debt rated D is in payment default. The D rating category is
            used when interest payments or principal payments are not made on
            the date due, even if the applicable grace period has not expired,
            unless S&P believes that such payments will be made during such
            grace period.
               A commercial paper rating is not a recommendation to purchase,
            sell or hold a security inasmuch as it does not comment as to mar-
            ket price or suitability for a particular investor. The ratings
            are based on current information furnished to S&P by the issuer or
            obtained from other sources it considers reliable. S&P does not
            perform an audit in connection with any rating and may, on occa-
            sion, rely on unaudited financial information. The ratings may be
            changed, suspended, or withdrawn as a result of changes in or un-
            availability of such information.
 
34
 PIMCO Funds: Pacific Investment Management Series
<PAGE>
 
<TABLE> 
<CAPTION> 
<C>                 <S> 
                    ------------------------------------------------------------------------------------------
PIMCO               INVESTMENT ADVISER AND ADMINISTRATOR
Total Return Fund   
                    Pacific Investment Management Company, 840 Newport Center Drive, Suite 300,
                    Newport Beach, CA 92660
                    ------------------------------------------------------------------------------------------
                    DISTRIBUTOR

                    PIMCO Funds Distributors LLC, 2187 Atlantic Street, Stamford, CT 06902
                    ------------------------------------------------------------------------------------------
                    CUSTODIAN

                    Investors Fiduciary Trust Company, 801 Pennsylvania, Kansas City, MO 64105
                    ------------------------------------------------------------------------------------------
                    SHAREHOLDER SERVICING AGENT AND TRANSFER AGENT

                    Shareholder Services, Inc., P.O. Box 5866, Denver, CO 80217
                    To be changed to:
                    First Data Investor Services Group, Inc., P.O. Box 9688, Providence, RI 02940-9688
                    ------------------------------------------------------------------------------------------
                    INDEPENDENT ACCOUNTANTS

                    PricewaterhouseCoopers LLP, 1055 Broadway, Kansas City, MO 64105
                    ------------------------------------------------------------------------------------------
                    LEGAL COUNSEL

                    Dechert Price & Rhoads, 1775 Eye Street N.W., Washington, D.C. 20006
                    ------------------------------------------------------------------------------------------
                    For further information about the PIMCO Funds, call 1-800-426-0107 or visit our Web site  
                    at www.pimcofunds.com.
</TABLE> 
<PAGE>
 
                           PIMCO FUNDS IS ON THE WEB
                              www. pimcofunds.com

<TABLE> 
<S>                     <C>                           <C>                        <C> 
A Partial List of       PIMCO Funds Distributors                    
What's Available:       LLC is please to announce              
                        the launch of its Web              
Daily Manager           site. You and your            
Commentary              financial advisor now            [PICTURE]                  [PICTURE]
                        have around-the-clock         
Fund Manager Bios       access to the most            
                        timely and comprehensive      
Current and             information available         
Historical Fund         on all of the PIMCO           
Performance             Funds. In addition, the       INVESTMENT INSIGHT         RESOURCES
                        site includes daily           The Investment             Our Resources section features 
Lipper Rankings         commentary from our fund      Insight section            a variety of useful information,
                        managers, with insights       provides an overview       including:
Morningstar Ratings     on the economy and other      of six of the
                        factors affecting the         investment management      *an on-line document library
Listing of Fund         stock and bond markets.       firms under the PIMCO      that contains prospectuses,
Portfolio Holdings                                    Advisors L.P. umbrella.    applications and other forms
                                                      You'll find an             that you can view and print
Risk Analysis                                         explanation of each
                                                      firm's investment          *a literature-by-mail
Daily Share Prices            [PICTURE]               process, biographies       "catalog", so you can order
                                                      of the investment          free materials, such as our
Downloadable                                          team, manager updates      popular Investor Guide
Literature Section                                    and more.
                        You'll find the site to                                  *information about our
On-Line Literature      be informative and                                       convenient shareholder services,
Requests                easy-to-use. It's                                        such as Auto-Invest, Fund
                        divided into three main           [PICTURE]              Link and our 24-Hour
Resources for           sections: Investment                                     Telephone Information System
Investment              Insight, Fund
Professionals           Information and                                          *a listing of the features and
                        Resources. And there                                     benefits of the retirement plans
                        are several functions         FUND INFORMATION           offered by PIMCO Funds.
                        that can help you             In the Fund
                        navigate your way             Information section        QUESTIONS?
                        around the site. We can       you'll access detailed     We're sure you'll find the
                        be found on the               profiles of all the        PIMCO Funds Web site to be
                        Worldwide Web at              PIMCO Funds, including     an invaluable tool. If you
                        www.pimcofunds.com.           current and historical     have any comments or questions
                                                      performance, Lipper        about the site, please call us
                                                      rankings and Morningstar   today at 1-800-426-0107. Or, use
                                                      ratings. Additionally,     the e-mail feature of the site
                                                      we provide a summary of    to contact us.
                                                      a fund's portfolio--
                                                      complete with risk
                                                      analysis data. You can
                                                      also obtain daily fund
                                                      share prices. Please
                                                      read the relevant
                                                      prospectus carefully
                                                      before you invest
                                                      in any PIMCO Fund.


                                                                                                 P I M C O
                                                                                                 ---------
                                                                                                     FUNDS
</TABLE>



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