UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM N-CSR

              CERTIFIED SHAREHOLDER REPORT OF REGISTERED MANAGEMENT
                              INVESTMENT COMPANIES

                  Investment Company Act file number 811-01311

                            The Gabelli Mathers Fund
            --------------------------------------------------------
               (Exact name of registrant as specified in charter)

                              One Corporate Center
                            Rye, New York 10580-1422
            --------------------------------------------------------
               (Address of principal executive offices) (Zip code)

                                 Bruce N. Alpert
                               Gabelli Funds, LLC
                              One Corporate Center
                            Rye, New York 10580-1422
            --------------------------------------------------------
                     (Name and address of agent for service)

       registrant's telephone number, including area code: 1-800-422-3554
                                                           --------------
                   Date of fiscal year end: December 31, 2004
                                            -----------------
                     Date of reporting period: June 30, 2004
                                               -------------


Form N-CSR is to be used by management investment companies to file reports with
the Commission not later than 10 days after the  transmission to stockholders of
any report that is required to be transmitted to  stockholders  under Rule 30e-1
under the Investment Company Act of 1940 (17 CFR 270.30e-1).  The Commission may
use the information provided on Form N-CSR in its regulatory, disclosure review,
inspection, and policymaking roles.

A registrant  is required to disclose the  information  specified by Form N-CSR,
and the  Commission  will make this  information  public.  A  registrant  is not
required to respond to the  collection  of  information  contained in Form N-CSR
unless the Form  displays a  currently  valid  Office of  Management  and Budget
("OMB")  control number.  Please direct comments  concerning the accuracy of the
information  collection  burden  estimate and any  suggestions  for reducing the
burden to Secretary,  Securities and Exchange Commission,  450 Fifth Street, NW,
Washington,  DC 20549-0609.  The OMB has reviewed this collection of information
under the clearance requirements of 44 U.S.C. ss. 3507.





ITEM 1. REPORTS TO STOCKHOLDERS.

The Report to Shareholders is attached herewith.





                            THE GABELLI MATHERS FUND

                               SEMI-ANNUAL REPORT
                                  JUNE 30, 2004



TO OUR SHAREHOLDERS,

      In our June 30, 2003  report,  we noted a change in the way we provide the
portfolio  manager's  commentary to shareholders  of our Funds.  Our shareholder
reports  have  typically  contained   commentary  on  each  portfolio  manager's
assessment of the stock market, individual stocks and how economic events affect
their  thinking in managing a specific  Fund.  We have always  provided  details
about performance and presented returns, both good and bad, hopefully in a clear
and concise  fashion.  These  comments have been included as part of each Fund's
quarterly, semi-annual, and annual financial statements.

      The Sarbanes-Oxley Act's corporate governance regulations require a Fund's
principal executive and financial officers to certify the entire contents of the
semi-annual and annual  shareholder  reports in a filing with the Securities and
Exchange  Commission  on Form N-CSR.  This  certification  covers the  portfolio
manager's  commentary and subjective  opinions if they are attached to or a part
of the financial statements.

      Rather than ask our portfolio  managers to eliminate their opinions and/or
restrict  their   commentary  to  historical  facts  only,  we  separated  their
commentary from the financial statements and investment portfolio and sent it to
you  separately  during our December 31, 2003  mailing.  We continue to mail the
portfolio  manager's  commentary  separately  from the  investment  portfolio to
ensure that its content is complete and  unrestricted.  Both the  commentary and
the  financial  statements,  including the  portfolio of  investments,  are also
available on our website at www.gabelli.com/funds.

      We  trust  that  you  understand   that  our  approach  is  an  unintended
consequence of the  ever-increasing  regulatory  requirements  affecting  public
companies generally.  We hope the specific  certification  requirements of these
regulations  will be modified as they relate to mutual funds,  since  investment
companies have different  corporate  structures and objectives than other public
companies.

                                                        Sincerely yours,

                                                        /s/Bruce N. Alpert
                                                        Bruce N. Alpert
                                                        Chief Operating Officer
                                                        Gabelli Funds
August 10, 2004


- --------------------------------------------------------------------------------
 A description  of the Fund's proxy voting  policies and  procedures and how the
 Fund voted  proxies  relating to  portfolio  securities  during the most recent
 12-month  period ended June 30, 2004 are  available  (i) without  charge,  upon
 request, by calling 800-GABELLI (800-422-3554);  (ii) by writing to The Gabelli
 Funds at One Corporate Center, Rye, NY 10580-1422;  and (iii) on the Securities
 and Exchange Commission's website at www.sec.gov.
- --------------------------------------------------------------------------------



THE GABELLI MATHERS FUND
PORTFOLIO OF INVESTMENTS -- JUNE 30, 2004 (UNAUDITED)
- --------------------------------------------------------------------------------

                                                                        MARKET
      SHARES                                              COST          VALUE
      -------                                             ----         -------
              COMMON STOCKS -- 4.6%
              BROADCASTING -- 0.6%
      15,000  Liberty Media Corp., Cl. A+ .........   $   135,270   $   134,850
       4,000  Liberty Media International
                Inc., Cl. A+ ......................       142,331       148,400
                                                      -----------   -----------
                                                          277,601       283,250
                                                      -----------   -----------
              BUSINESS SERVICES -- 0.0%
         500  Kroll Inc.+ .........................        18,430        18,440
                                                      -----------   -----------
              COMPUTER SOFTWARE AND SERVICES -- 0.4%
       5,000  CACI International Inc., Cl. A+ .....       189,189       202,200
                                                      -----------   -----------
              ENERGY AND UTILITIES -- 1.1%
         500  Anadarko Petroleum Corp. ............        22,080        29,300
         500  Cinergy Corp. .......................        18,045        19,000
       1,000  Duquesne Light Holdings Inc. ........        15,295        19,310
         500  Murphy Oil Corp. ....................        29,891        36,850
      15,000  Unisource Energy Corp. ..............       369,917       372,750
                                                      -----------   -----------
                                                          455,228       477,210
                                                      -----------   -----------
              ENTERTAINMENT -- 1.1%
      40,000  Metro-Goldwyn-Mayer Inc.+ ...........       494,071       484,000
                                                      -----------   -----------
              FINANCIAL SERVICES -- 0.2%
         500  MONY Group Inc. .....................        16,635        15,650
       1,000  Quaker City Bancorp Inc. ............        54,390        54,940
                                                      -----------   -----------
                                                           71,025        70,590
                                                      -----------   -----------
              FOOD AND BEVERAGE -- 0.2%
         500  Dreyer's Grand Ice Cream
                Holdings Inc., Cl. A ..............        39,595        39,545
       2,000  Hain Celestial Group Inc.+ ..........        36,041        36,200
                                                      -----------   -----------
                                                           75,636        75,745
                                                      -----------   -----------
              HEALTH CARE -- 0.4%
       5,000  CIMA Labs Inc.+ .....................       165,053       168,650
                                                      -----------   -----------
              HOTELS AND GAMING -- 0.1%
         500  Mandalay Resort Group ...............        34,035        34,320
                                                      -----------   -----------
              RETAIL -- 0.1%
       3,000  Cole National Corp.+ ................        66,180        70,050
                                                      -----------   -----------
              SATELLITE -- 0.0%
         500  PanAmSat Corp.+ .....................        11,635        11,610
                                                      -----------   -----------
              TELECOMMUNICATIONS -- 0.2%
       1,000  BellSouth Corp. .....................        24,080        26,220
       1,000  SBC Communications Inc. .............        22,310        24,250
       1,000  Verizon Communications Inc. .........        32,920        36,190
                                                      -----------   -----------
                                                           79,310        86,660
                                                      -----------   -----------
              WIRELESS COMMUNICATIONS -- 0.2%
       5,000  AT&T Wireless Services Inc.+ ........        70,320        71,600
                                                      -----------   -----------
              TOTAL COMMON STOCKS .................     2,007,713     2,054,325
                                                      -----------   -----------

     PRINCIPAL
      AMOUNT
     ---------
              U.S. GOVERNMENT  OBLIGATIONS -- 91.5%
 $41,000,000  U.S. Treasury Bill,
                0.943%++, 07/01/04 (a) ............    41,000,000    41,000,000
                                                      -----------   -----------

     PRINCIPAL                                                         MARKET
      AMOUNT                                              COST          VALUE
     ---------                                            ----         -------
              REPURCHASE AGREEMENTS -- 4.3%
 $ 1,950,105  State Street Bank & Trust Co.,
                1.180%, dated 06/30/04,
                due 07/01/04, proceeds at
                maturity, $1,950,168 (b) ..........   $ 1,950,105   $ 1,950,105
                                                      -----------   -----------
              TOTAL INVESTMENTS -- 100.4% .........   $44,957,818    45,004,429
                                                      ===========
              OTHER ASSETS AND LIABILITIES (NET) -- (0.4)%             (179,805)
                                                                    -----------
              NET ASSETS -- 100.0%                                  $44,824,624
                                                                    ===========
              SECURITIES SOLD SHORT -- (7.4)%

        SHARES                                         PROCEEDS
       -------                                         --------
              COMMON STOCKS -- (7.4)%
              AUTOMOTIVE -- (0.2)%
       6,000  Ford Motor Co. ......................   $    90,878   $    93,900
                                                      -----------   -----------
              CONSUMER PRODUCTS -- (1.4)%
      13,500  Polaris Industries Inc. .............       484,964       648,000
                                                      -----------   -----------
              DIVERSIFIED -- (1.3)%
       5,000  Standard & Poor's
                Depository Receipts ...............       564,802       572,650
                                                      -----------   -----------
              ELECTRONICS -- (0.2)%
       2,000  Semiconductor HOLDRs Trust ..........        74,765        75,540
                                                      -----------   -----------
              ENTERTAINMENT -- (0.6)%
       6,000  Carnival Corp. ......................       233,538       282,000
                                                      -----------   -----------
              FINANCIAL SERVICES -- (0.1)%
         500  Fannie Mae ..........................        38,895        35,680
                                                      -----------   -----------
              HOME FURNISHINGS -- (0.7)%
       4,000  Ethan Allen Interiors Inc. ..........       157,125       143,640
       9,000  La-Z-Boy Inc. .......................       187,298       161,820
                                                      -----------   -----------
                                                          344,423       305,460
                                                      -----------   -----------
              RESTAURANTS -- (0.6)%
       3,000  Cheesecake Factory Inc.+ ............       108,342       119,370
       5,000  McDonald's Corp. ....................       125,858       130,000
                                                      -----------   -----------
                                                          234,200       249,370
                                                      -----------   -----------
              RETAIL -- (2.3)%
       4,000  Gap Inc. ............................        79,766        97,000
       2,000  Kohl's Corp.+ .......................        95,259        84,560
      11,000  May Department Stores Co. ...........       310,069       302,390
       5,000  The Home Depot Inc. .................       161,867       176,000
       6,000  Tiffany & Co. .......................       167,392       221,100
       6,000  Zale Corp.+ .........................       153,454       163,560
                                                      -----------   -----------
                                                          967,808     1,044,610
                                                      -----------   -----------
              TOTAL SECURITIES
                SOLD SHORT ........................   $ 3,034,272   $ 3,307,210
                                                      ===========   ===========
- ----------------
              For Federal tax purposes:
              Aggregate cost ...................................    $44,957,818
                                                                    ===========
              Gross unrealized appreciation ....................    $    58,163
              Gross unrealized depreciation ....................        (11,552)
                                                                    -----------
              Net unrealized appreciation/(depreciation) .......    $    46,611
                                                                    ===========
- ----------------
(a) At June 30, 2004, $25,000,000 of the principal amount was pledged as
    collateral for securities sold short.
(b) Collateralized by U.S. Treasury Bond, 8.000%, due 11/15/21, market value
    $1,989,621.
 +  Non-income producing security.
 ++ Represents annualized yield at date of purchase.

                See accompanying notes to financial statements.

                                        2



                            THE GABELLI MATHERS FUND

STATEMENT OF ASSETS AND LIABILITIES
JUNE 30, 2004 (UNAUDITED)
- --------------------------------------------------------------------------------
ASSETS:
  Investments, at value (cost $44,957,818) ....................   $ 45,004,429
  Deposit at brokers ..........................................      3,301,213
  Dividends and interest receivable ...........................          1,176
  Receivable for investments sold .............................         44,000
  Other assets ................................................          2,237
                                                                  ------------
  TOTAL ASSETS ................................................     48,353,055
                                                                  ------------
LIABILITIES:
  Securities sold short (proceeds $3,034,272) .................      3,307,210
  Payable for investments purchased ...........................         75,005
  Dividends  payable on securities sold short .................          2,810
  Payable for investment advisory fees ........................         36,951
  Payable for  distribution fees ..............................          9,238
  Other accrued expenses and liabilities ......................         97,217
                                                                  ------------
  TOTAL LIABILITIES ...........................................      3,528,431
                                                                  ------------
  NET ASSETS applicable to 4,261,993
    shares outstanding ........................................   $ 44,824,624
                                                                  ============
NET ASSETS CONSIST OF:
  Shares of beneficial interest, $1.00 par value ..............   $  4,261,993
  Additional paid-in capital ..................................     84,458,493
  Accumulated net investment loss .............................       (250,241)
  Accumulated net realized loss on investments
    and securities sold short .................................    (43,419,294)
  Net unrealized depreciation on securities
    sold short ................................................       (272,938)
  Net unrealized appreciation on investments ..................         46,611
                                                                  ------------
  NET ASSETS ..................................................   $ 44,824,624
                                                                  ============
  NET ASSET VALUE, offering and redemption price
    per share ($44,824,624 / 4,261,993 shares
    outstanding;100,000,000 shares authorized) ................         $10.52
                                                                        ======


STATEMENT OF OPERATIONS
FOR THE SIX MONTHS ENDED JUNE 30, 2004 (UNAUDITED)
- --------------------------------------------------------------------------------
INVESTMENT INCOME:
  Dividends ......................................................   $  16,102
  Interest .......................................................     227,946
  Other income ...................................................      10,178
                                                                     ---------
  TOTAL INVESTMENT INCOME ........................................     254,226
                                                                     ---------
EXPENSES:
  Investment advisory fees .......................................     260,508
  Distribution fees ..............................................      65,127
  Trustees' fees .................................................      29,135
  Dividends on securities sold short .............................      28,539
  Shareholder services fees ......................................      24,289
  Custodian fees .................................................      23,336
  Shareholder communications expenses ............................      23,150
  Legal and audit fees ...........................................      15,950
  Registration fees ..............................................      10,396
  Miscellaneous expenses .........................................      24,037
                                                                     ---------
  TOTAL EXPENSES .................................................     504,467
                                                                     ---------
  NET INVESTMENT LOSS ............................................    (250,241)
                                                                     ---------
NET REALIZED AND UNREALIZED GAIN (LOSS) ON
  INVESTMENTS AND SECURITIES SOLD SHORT:
  Net realized gain on investments ...............................     124,473
  Net realized loss on securities sold short .....................    (346,537)
  Net change in unrealized appreciation/
    depreciation on investments and
    securities sold short ........................................      21,232
                                                                     ---------
  NET REALIZED AND UNREALIZED LOSS ON
    INVESTMENTS AND SECURITIES SOLD SHORT ........................    (200,832)
                                                                     ---------
  NET DECREASE IN NET ASSETS RESULTING
    FROM OPERATIONS ..............................................   $(451,073)
                                                                     =========



STATEMENT OF CHANGES IN NET ASSETS
- --------------------------------------------------------------------------------

                                                                                SIX MONTHS ENDED
                                                                                  JUNE 30, 2004      YEAR ENDED
                                                                                   (UNAUDITED)    DECEMBER 31, 2003
                                                                                ----------------  ------------------
OPERATIONS:
                                                                                               
  Net investment loss ........................................................   $   (250,241)       $   (456,610)
  Net realized gain (loss) on investments ....................................        124,473            (132,253)
  Net realized loss on securities sold short .................................       (346,537)           (537,948)
  Net change in unrealized appreciation/depreciation on investments and
    securities sold short ....................................................         21,232            (356,240)
                                                                                 ------------        ------------
  NET DECREASE IN NET ASSETS RESULTING FROM OPERATIONS .......................       (451,073)         (1,483,051)
                                                                                 ------------        ------------
SHARES OF BENEFICIAL INTEREST TRANSACTIONS:
  Net decrease in net assets from shares of beneficial interest transactions .    (15,569,828)        (18,498,603)
                                                                                 ------------        ------------
  NET DECREASE IN NET ASSETS .................................................    (16,020,901)        (19,981,654)
NET ASSETS:
  Beginning of period ........................................................     60,845,525          80,827,179
                                                                                 ------------        ------------
  End of period ..............................................................   $ 44,824,624        $ 60,845,525
                                                                                 ============        ============



                See accompanying notes to financial statements.

                                        3



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (UNAUDITED)
- --------------------------------------------------------------------------------
1. ORGANIZATION. The Gabelli Mathers Fund (the "Fund") was organized on June 17,
1999 as a Delaware statutory trust. The Fund commenced investment  operations on
October 1, 1999 as the successor to the Mathers Fund,  Inc. (the "Mathers Fund")
which was  organized  on March 31, 1965 as a Maryland  corporation.  The Mathers
Fund  commenced  investment  operations  on  August  19,  1965.  The  Fund  is a
diversified,   open-end  management  investment  company  registered  under  the
Investment  Company Act of 1940, as amended (the "1940 Act"). The Fund's primary
objective is long-term capital appreciation.

2. SIGNIFICANT  ACCOUNTING POLICIES.  The preparation of financial statements in
accordance  with  U.S.  generally  accepted   accounting   principles   requires
management to make estimates and  assumptions  that affect the reported  amounts
and  disclosures in the financial  statements.  Actual results could differ from
those estimates.  The following is a summary of significant  accounting policies
followed by the Fund in the preparation of its financial statements.

SECURITY  VALUATION.  Portfolio  securities  listed or  traded  on a  nationally
recognized securities exchange or traded in the U.S. over-the-counter market for
which market quotations are readily available are valued at the last quoted sale
price or a market's  official  closing  price as of the close of business on the
day the  securities  are being  valued.  If there  were no sales  that day,  the
security is valued at the  average of the  closing  bid and asked  prices or, if
there were no asked  prices  quoted on that day,  then the security is valued at
the closing bid price on that day. If no bid or asked  prices are quoted on such
day,  the  security is valued at the most  recently  available  price or, if the
Board of Trustees (the "Board") so determines, by such other method as the Board
shall  determine  in good faith,  to reflect its fair  market  value.  Portfolio
securities  traded on more than one national  securities  exchange or market are
valued according to the broadest and most  representative  market, as determined
by Gabelli Funds, LLC (the "Adviser").

Portfolio securities primarily traded on foreign markets are generally valued at
the preceding closing values of such securities on their respective exchanges or
if after the close,  market  conditions  change  significantly,  certain foreign
securities may be fair valued  pursuant to procedures  established by the Board.
Debt  instruments  that are not credit impaired with remaining  maturities of 60
days or less are valued at amortized cost, unless the Board determines such does
not reflect the securities'  fair value, in which case these  securities will be
valued at their fair value as determined by the Board. Debt instruments having a
maturity greater than 60 days for which market  quotations are readily available
are valued at the latest  average of the bid and asked prices.  If there were no
asked  prices  quoted on such day,  the security is valued using the closing bid
price.  Futures contracts are valued at the official closing settlement price of
the exchange or board of trade on which the applicable contract is traded.

Securities and assets for which market  quotations are not readily available are
valued  at their  fair  value  as  determined  in good  faith  under  procedures
established by and under the general  supervision  of the Board.  Fair valuation
methodologies  and procedures may include,  but are not limited to: analysis and
review of available  financial and non-financial  information about the company;
comparisons  to the  valuation  and changes in valuation of similar  securities,
including a comparison of foreign securities to the equivalent U.S. dollar value
ADR  securities at the close of the U.S.  exchange;  and evaluation of any other
information that could be indicative of the value of the security.

REPURCHASE  AGREEMENTS.  The Fund may  enter  into  repurchase  agreements  with
primary  government  securities dealers recognized by the Federal Reserve Board,
with member banks of the Federal Reserve System or with other brokers or dealers
that meet credit  guidelines  established  by the  Adviser  and  reviewed by the
Board.  Under  the  terms of a  typical  repurchase  agreement,  the Fund  takes
possession  of an  underlying  debt  obligation  subject to an obligation of the
seller to repurchase,  and the Fund to resell,  the obligation at an

                                       4



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------
agreed-upon  price and time,  thereby  determining  the yield  during the Fund's
holding  period.  The Fund  will  always  receive  and  maintain  securities  as
collateral  whose market value,  including  accrued  interest,  will be at least
equal to 102% of the dollar amount invested by the Fund in each  agreement.  The
Fund will make payment for such securities  only upon physical  delivery or upon
evidence  of  book  entry  transfer  of the  collateral  to the  account  of the
custodian.  To the extent that any repurchase  transaction  exceeds one business
day,  the  value  of the  collateral  is  marked-to-market  on a daily  basis to
maintain the adequacy of the collateral. If the seller defaults and the value of
the collateral declines or if bankruptcy  proceedings are commenced with respect
to the seller of the security,  realization of the collateral by the Fund may be
delayed or limited.

FUTURES  CONTRACTS.  The Fund may engage in futures contracts for the purpose of
hedging  against  changes in the value of its  portfolio  securities  and in the
value of  securities  it  intends  to  purchase.  Upon  entering  into a futures
contract,  the Fund is required to deposit  with the broker an amount of cash or
cash equivalents equal to a certain  percentage of the contract amount.  This is
known as the "initial margin." Subsequent payments ("variation margin") are made
or  received by the Fund each day,  depending  on the daily  fluctuation  in the
value of the  contract.  The daily  changes  in the  contract  are  included  in
unrealized gains or losses. The Fund recognizes a realized gain or loss when the
contract is closed. At June 30, 2004, there were no open futures contracts.

There are several  risks in  connection  with the use of futures  contracts as a
hedging device. The change in value of futures contracts  primarily  corresponds
with the value of their underlying instruments, which may not correlate with the
change in value of the hedged investments.  In addition,  there is the risk that
the Fund may not be able to  enter  into a  closing  transaction  because  of an
illiquid secondary market.

SECURITIES  SOLD SHORT. A short sale involves  selling a security which the Fund
does not own. The proceeds  received for short sales are recorded as liabilities
and the Fund records an unrealized  gain or loss to the extent of the difference
between the proceeds  received  and the value of the open short  position on the
day of  determination.  The Fund records a realized  gain or loss when the short
position is closed out. By entering into a short sale, the Fund bears the market
risk of an unfavorable change in price of the security sold short.  Dividends on
short sales are recorded as an expense by the Fund on the  ex-dividend  date and
interest expense is recorded on the accrual basis. Securities sold short at June
30, 2004 are reflected in the Portfolio of Investments.

SECURITIES  TRANSACTIONS  AND INVESTMENT  INCOME.  Securities  transactions  are
accounted  for on the  trade  date  with  realized  gain or loss on  investments
determined  by using the  identified  cost method.  Interest  income  (including
amortization  of premium  and  accretion  of  discount)  is  recorded as earned.
Dividend income is recorded on the ex-dividend date.

DIVIDENDS AND  DISTRIBUTIONS  TO  SHAREHOLDERS.  Dividends and  distributions to
shareholders  are recorded on the ex-dividend  date.  Income  distributions  and
capital  gain  distributions  are  determined  in  accordance  with  income  tax
regulations which may differ from generally  accepted  accounting  principles in
the United States.  These differences are primarily due to differing  treatments
of income and gains on various  investment  securities held by the Fund,  timing
differences and differing characterization of distributions made by the Fund.

No distributions  were made in the six months ended June 30, 2004 and the fiscal
year ended December 31, 2003.

For the year ended  December 31, 2003,  reclassifications  were made to decrease
accumulated  net investment  loss for $456,610 and to decrease  accumulated  net
realized loss on investments  for $4,819,701,  with an offsetting  adjustment to
additional paid-in capital.

                                       5



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------
PROVISION  FOR  INCOME  TAXES.  The Fund  intends  to  continue  to qualify as a
regulated  investment company under Subchapter M of the Internal Revenue Code of
1986, as amended (the "Code").  As a result,  a Federal  income tax provision is
not required.

As of December 31, 2003, the components of  accumulated  earnings/(losses)  on a
tax basis were as follows:

       Accumulated capital loss carryforward .....  $(43,197,230)
       Net unrealized appreciation/(depreciation)
         of investments ..........................       143,125
       Net unrealized appreciation/(depreciation)
         of securities sold short ................      (390,684)
                                                    ------------
       Total accumulated loss ....................  $(43,444,789)
                                                    ============

The Fund has a net capital loss  carryforward for Federal income tax purposes at
December 31, 2003 of $43,197,230. This capital loss carryforward is available to
reduce future distributions of net capital gains to shareholders. $22,226,886 of
the loss carryforward is available through 2004; $7,869,968 is available through
2006;  $12,430,175 is available  through 2010; and $670,201 is available through
2011.

3.  INVESTMENT  ADVISORY  AGREEMENT.  The Fund has  entered  into an  Investment
Advisory  Agreement (the "Advisory  Agreement")  with the Adviser which provides
that the Fund will pay the Adviser a fee,  computed  daily and paid monthly,  at
the  annual  rate of 1.00% of the value of the Fund's  average  net  assets.  In
accordance  with the  Advisory  Agreement,  the  Adviser  provides a  continuous
investment program for the Fund's portfolio,  oversees the administration of all
aspects of the Fund's  business  and  affairs and pays the  compensation  of all
Officers and Trustees of the Fund who are its affiliates.

4.  DISTRIBUTION   PLAN.  On  October  1,  1999,  the  Fund's  Board  adopted  a
distribution  plan (the  "Plan")  pursuant to Rule 12b-1 under the 1940 Act. For
the six months ended June 30, 2004, the Fund incurred distribution costs payable
to Gabelli & Company, Inc., an affiliate of the Adviser, of $65,127, or 0.25% of
average daily net assets,  the annual  limitation  under the Plan. Such payments
are accrued daily and paid monthly.

5. PORTFOLIO SECURITIES. Purchases and proceeds from the sales of securities for
the six months ended June 30, 2004, other than short term securities, aggregated
$3,261,314 and $4,402,071, respectively.

6. TRANSACTIONS WITH AFFILIATES.  During the six months ended June 30, 2004, the
Fund paid brokerage commissions of $50 to Gabelli & Company, Inc.

The cost of  calculating  the Fund's net asset value per share is a Fund expense
pursuant to the Advisory  Agreement between the Fund and the Adviser. During the
six months  ended June 30,  2004,  the Fund  reimbursed  the  Adviser  $8,700 in
connection  with the cost of  computing  the  Fund's net asset  value,  which is
included in miscellaneous expenses in the Statement of Operations.

7. SHARES OF BENEFICIAL INTEREST.  Transactions in shares of beneficial interest
were as follows:

                             SIX MONTHS ENDED
                               JUNE 30, 2004                YEAR ENDED
                                (UNAUDITED)             DECEMBER 31, 2003
                       -------------------------    -------------------------
                          SHARES        AMOUNT         SHARES        AMOUNT
                       ----------   ------------    ----------   ------------
Shares sold .........     222,718   $  2,361,582       271,933   $  2,922,779
Shares redeemed .....  (1,699,341)   (17,931,411)   (2,007,763)   (21,421,382)
                       ----------   ------------    ----------   ------------
    Net decrease ....  (1,476,623)  $(15,569,828)   (1,735,830)  $(18,498,603)
                       ==========   ============    ==========   ============

                                       6



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------
8. OTHER MATTERS.  On October 7, 2003,  the Fund's  Adviser  received a subpoena
from the Attorney  General of the State of New York  requesting  information  on
mutual fund shares trading practices. The Adviser has also received requests for
information from the SEC regarding  mutual fund trading  practices and valuation
of portfolio  securities.  The Adviser has responded to the  requests.  The Fund
does not believe that these matters will have a material  adverse  effect on the
Fund's financial position or the results of its operations.

9.  INDEMNIFICATIONS.  The Fund enters into  contracts that contain a variety of
indemnifications. The  Fund's  maximum  exposure  under  these  arrangements  is
unknown.  However, the Fund has not had prior claims or losses pursuant to these
contracts and expects the risk of loss to be remote.

10.  FINANCIAL  HIGHLIGHTS.  Selected  data for a share of  beneficial  interest
outstanding throughout each period:




                                         SIX MONTHS ENDED                      YEAR ENDED DECEMBER 31,
                                           JUNE 30, 2004    -----------------------------------------------------------
                                            (UNAUDITED)      2003         2002          2001        2000         1999(A)
                                              -------       -------     --------      -------      -------      -------
OPERATING PERFORMANCE:
                                                                                              
   Net asset value, beginning of period ...   $ 10.60       $ 10.81     $  12.25      $ 12.05      $ 11.94     $  11.73
                                              -------       -------     --------      -------      -------     --------
   Net investment income (loss) ...........     (0.05)        (0.07)       (0.00)(b)     0.30         0.49         0.46
   Net realized and unrealized
     gain/(loss) on investments ...........     (0.03)        (0.14)       (1.44)        0.21         0.11         0.21
                                              -------       -------     --------      -------      -------     --------
   Total from investment operations .......     (0.08)        (0.21)       (1.44)        0.51         0.60         0.67
                                              -------       -------     --------      -------      -------     --------
DISTRIBUTIONS TO SHAREHOLDERS:
   Net investment income ..................        --            --           --        (0.31)       (0.49)       (0.46)
                                              -------       -------     --------      -------      -------     --------
   Total distributions ....................        --            --           --        (0.31)       (0.49)       (0.46)
                                              -------       -------     --------      -------      -------     --------
   NET ASSET VALUE, END OF PERIOD .........   $ 10.52       $ 10.60     $  10.81      $ 12.25      $ 12.05     $  11.94
                                              =======       =======     ========      =======      =======     ========
   Total return+ ..........................     (0.75)%       (1.94)%     (11.76)%       4.25%        5.02%        5.73%
                                              =======       =======     ========      =======      =======     ========
RATIOS TO AVERAGE NET ASSETS
   AND SUPPLEMENTAL DATA:
   Net assets, end of period (in 000's) ...   $44,825       $60,846     $ 80,827      $97,893      $99,855     $104,693
   Ratio of net investment income
     to average net assets ................     (0.96)%(c)    (0.61)%      (0.00)%       2.45%        3.79%        3.50%
   Ratio of operating expenses
     to average net assets ................      1.94%(c)      1.67%        1.63%        1.35%        1.34%        1.24%
   Portfolio turnover rate ................       139%          244%         776%        1013%         977%         922%


- --------------------------------------------------------------------------------
+   Total return  represents  aggregate  total return of a  hypothetical  $1,000
    investment  at the beginning of the period and sold at the end of the period
    including  reinvestment  of  dividends.  Total return for the period of less
    than one year is not annualized.
(a) Gabelli Funds, LLC became the sole investment adviser of the Fund on October
    1, 1999.
(b) Amount is less than $0.005 per share.
(c) Annualized.

                 See accompanying notes to financial statements.

                                       7



                 THE GABELLI MATHERS FUND
                   One Corporate Center
                 Rye, New York 10580-1422
                        800-GABELLI
                       800-422-3554
                     FAX: 914-921-5118
                 WEBSITE: WWW.GABELLI.COM
                 E-MAIL: INFO@GABELLI.COM
        Net Asset Value available daily by calling
                800-GABELLI after 6:00 P.M.

                      BOARD OF TRUSTEES

   Mario J. Gabelli, CFA           Anthony R. Pustorino
   CHAIRMAN AND CHIEF              CERTIFIED PUBLIC ACCOUNTANT
   INVESTMENT OFFICER              PROFESSOR, PACE UNIVERSITY
   GABELLI ASSET MANAGEMENT INC.

   E. Val Cerutti                  Werner J. Roeder, MD
   CHIEF EXECUTIVE OFFICER         VICE PRESIDENT/MEDICAL AFFAIRS
   CERUTTI CONSULTANTS, INC.       LAWRENCE HOSPITAL CENTER

   Anthony J. Colavita             Henry G. Van der Eb, CFA
   ATTORNEY-AT-LAW                 PRESIDENT AND CHIEF
   ANTHONY J. COLAVITA, P.C.       EXECUTIVE OFFICER
                                   THE GABELLI MATHERS FUND

   Vincent D. Enright              Anthonie C. van Ekris
   FORMER SENIOR VICE PRESIDENT    MANAGING DIRECTOR
   AND CHIEF FINANCIAL OFFICER     BALMAC INTERNATIONAL, INC.
   KEYSPAN ENERGY CORP.

   Karl Otto Pohl
   FORMER PRESIDENT
   DEUTSCHE BUNDESBANK


                OFFICERS AND PORTFOLIO MANAGER

   Henry G. Van der Eb, CFA        Anne E. Morrissy, CFA
   PRESIDENT AND                   EXECUTIVE VICE PRESIDENT
   PORTFOLIO MANAGER

   Bruce N. Alpert                 James E. McKee
   EXECUTIVE VICE PRESIDENT        VICE PRESIDENT
   AND TREASURER                   AND SECRETARY

   Heidi M. Stubner                Edith L. Cook
   VICE PRESIDENT                  VICE PRESIDENT

                          DISTRIBUTOR
                    Gabelli & Company, Inc.

         CUSTODIAN, TRANSFER AGENT AND DIVIDEND AGENT
              State Street Bank and Trust Company

                         LEGAL COUNSEL
           Skadden, Arps, Slate, Meagher & Flom LLP

- --------------------------------------------------------------------------------
This report is submitted for the general  information of the shareholders of The
Gabelli  Mathers Fund. It is not  authorized  for  distribution  to  prospective
investors unless preceded or accompanied by an effective prospectus.
- --------------------------------------------------------------------------------

                                                   [MARIO GABELLI PHOTO OMITTED]
THE
GABELLI
MATHERS
FUND


                                                              SEMI-ANNUAL REPORT
                                                                   JUNE 30, 2004


GAB1726Q204SR


ITEM 2. CODE OF ETHICS.

Not applicable.



ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.

Not applicable.



ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

Not applicable.



ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS.

Not applicable.



ITEM 6. SCHEDULE OF INVESTMENTS

Not applicable.



ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END
        MANAGEMENT INVESTMENT COMPANIES.

Not applicable.



ITEM 8. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT
        COMPANY AND AFFILIATED PURCHASERS.

Not applicable.







ITEM 9. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

The  Board  of  Trustees   has  a   Nominating   Committee   comprised   of  two
"non-interested" (as such term is defined by the Investment Company Act of 1940,
as amended)  Trustees,  namely  Anthony J. Colavita,  and Werner J. Roeder.  The
Nominating  Committee is responsible for identifying  individuals believed to be
qualified  to become  Board  members in the event that a position  is vacated or
created. The Nominating Committee will consider Trustees candidates  recommended
by  shareholders.  In  considering  candidates  submitted by  shareholders,  the
Nominating  Committee  will  take into  consideration  the needs of the Board of
Trustees, the qualifications of the candidate and the interests of shareholders.
The Nominating  Committee may also take into  consideration the number of shares
held by the  recommending  shareholder  and the length of time that such  shares
have been held. To have a candidate  considered by the Nominating  Committee,  a
shareholder  must  submit the  recommendation  in writing  and must  include the
following information:

     o    The name of the shareholder and evidence of the person's  ownership of
          shares  of the Fund,  including  the  number  of shares  owned and the
          length of time of ownership;

     o    The name of the candidate,  the candidate's resume or a listing of his
          or her  qualifications  to be a Trustee  of the Fund and the  person's
          consent  to be  named  as a  Trustee  if  selected  by the  Nominating
          Committee and nominated by the Board of Trustees; and

     o    If  requested  by the  Nominating  Committee,  a completed  and signed
          directors questionnaire.

The shareholder  recommendation and information  described above must be sent to
the Fund's Secretary c/o Gabelli Funds, LLC, James E. McKee and must be received
by the  Secretary  no less than 120 days  prior to the  anniversary  date of the
Fund's most recent annual meeting of  shareholders  or, if the meeting has moved
by more than 30 days, a reasonable amount of time before the meeting.

The Nominating Committee believes that the minimum qualifications for serving as
a  Trustee  of the  Fund are that the  individual  demonstrate,  by  significant
accomplishment in his or her field, an ability to make a meaningful contribution
to the Board of Trustees'  oversight of the business and affairs of the Fund and
have an impeccable  record and reputation for honest and ethical conduct in both
his or her professional  and personal  activities.  In addition,  the Nominating
Committee  examines  a  candidate's   specific   experiences  and  skills,  time
availability in light of other commitments,  potential conflicts of interest and
independence  from management and the Fund. The Nominating  Committee also seeks
to have  the  Board  of  Trustees  represent  a  diversity  of  backgrounds  and
experience.





ITEM 10. CONTROLS AND PROCEDURES.

     (a)  The registrant's principal executive and principal financial officers,
          or persons  performing  similar  functions,  have  concluded  that the
          registrant's  disclosure  controls and  procedures (as defined in Rule
          30a-3(c)  under the  Investment  Company Act of 1940,  as amended (the
          "1940 Act") (17 CFR 270.30a-3(c))) are effective,  as of a date within
          90 days of the filing date of the report that includes the  disclosure
          required  by this  paragraph,  based  on  their  evaluation  of  these
          controls and  procedures  required by Rule 30a-3(b) under the 1940 Act
          (17 CFR  270.30a-3(b))  and Rules  13a-15(b)  or  15d-15(b)  under the
          Securities  Exchange Act of 1934, as amended (17 CFR  240.13a-15(b) or
          240.15d-15(b)).


     (b)  There  were no  changes  in the  registrant's  internal  control  over
          financial  reporting (as defined in Rule  30a-3(d)  under the 1940 Act
          (17 CFR  270.30a-3(d))  that  occurred  during the  registrant's  last
          fiscal half-year (the registrant's second fiscal half-year in the case
          of an annual  report) that has materially  affected,  or is reasonably
          likely to materially  affect,  the registrant's  internal control over
          financial reporting.


ITEM 11. EXHIBITS.

     (a)(1)   Not applicable.

     (a)(2)   Certifications  pursuant to Rule  30a-2(a)  under the 1940 Act and
              Section 302 of the Sarbanes-Oxley Act of 2002 are attached hereto.

     (a)(3)   Not applicable.


     (b)      Certifications  pursuant to Rule  30a-2(a)  under the 1940 Act and
              Section 906 of the Sarbanes-Oxley Act of 2002 are attached hereto.





                                   SIGNATURES

Pursuant to the  requirements  of the  Securities  Exchange  Act of 1934 and the
Investment Company Act of 1940, the registrant has duly caused this report to be
signed on its behalf by the undersigned, thereunto duly authorized.

(registrant)               The Gabelli Mathers Fund
             -------------------------------------------------------------------

By (Signature and Title)*  /s/ BRUCE N. ALPERT
                         -------------------------------------------------------
                           Bruce N. Alpert, Principal Executive Officer


Date                       September 7, 2004
    ----------------------------------------------------------------------------


Pursuant to the  requirements  of the  Securities  Exchange  Act of 1934 and the
Investment  Company  Act of  1940,  this  report  has been  signed  below by the
following  persons on behalf of the  registrant and in the capacities and on the
dates indicated.


By (Signature and Title)*  /s/ BRUCE N. ALPERT
                         -------------------------------------------------------
                           Bruce N. Alpert, Principal Executive Officer and
                           Principal Financial Officer

Date                       September 7, 2004
    ----------------------------------------------------------------------------



* Print the name and title of each signing officer under his or her signature.