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
                                               -----------

                     Date of reporting period: June 30, 2005
                                               -------------

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, 2005



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 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 18, 2005



- --------------------------------------------------------------------------------
We  have  separated  the  portfolio  manager's  commentary  from  the  financial
statements  and  investment  portfolio due to corporate  governance  regulations
stipulated by the  Sarbanes-Oxley  Act of 2002. We have done this to ensure that
the content of the portfolio manager's commentary is unrestricted. The financial
statements and investment  portfolio are mailed separately.  Both the commentary
and the financial  statements,  including the portfolio of investments,  will be
available on our website at www.gabelli.com/funds.
- --------------------------------------------------------------------------------



THE GABELLI MATHERS FUND
DISCLOSURE OF FUND EXPENSES (UNAUDITED)
For the Six Month Period from January 1, 2005 through June 30, 2005
                                                                   EXPENSE TABLE
- --------------------------------------------------------------------------------
We believe it is important for you to understand the impact of fees and expenses
regarding  your  investment.  All mutual  funds have  operating  expenses.  As a
shareholder  of a fund,  you  incur  ongoing  costs,  which  include  costs  for
portfolio  management,  administrative  services,  and shareholder reports (like
this one), among others.  Operating  expenses,  which are deducted from a fund's
gross income,  directly  reduce the investment  return of a fund.  When a fund's
expenses are expressed as a percentage of its average net assets, this figure is
known as the expense  ratio.  The  following  examples  are intended to help you
understand  the  ongoing  costs (in  dollars) of  investing  in your Fund and to
compare these costs with those of other mutual funds.  The examples are based on
an  investment  of $1,000 made at the beginning of the period shown and held for
the entire period.

The Expense Table below illustrates your Fund's costs in two ways:

ACTUAL FUND  RETURN:  This section  provides  information  about actual  account
values and actual expenses. You may use this section to help you to estimate the
actual  expenses that you paid over the period after any fee waivers and expense
reimbursements.  The "Ending  Account  Value"  shown is derived  from the Fund's
ACTUAL return during the past six months,  and the "Expenses Paid During Period"
shows the dollar  amount  that would have been paid by an  investor  who started
with $1,000 in the Fund. You may use this information,  together with the amount
you invested, to estimate the expenses that you paid over the period.

To do so, simply  divide your account  value by $1,000 (for  example,  an $8,600
account value  divided by $1,000 = 8.6),  then multiply the result by the number
given for your Fund under the heading  "Expenses Paid During Period" to estimate
the expenses you paid during this period.

HYPOTHETICAL 5% RETURN:  This section provides  information  about  hypothetical
account  values and  hypothetical  expenses  based on the Fund's actual  expense
ratio. It assumes a hypothetical  annualized return of 5% before expenses during
the period shown.  In this case -- because the  hypothetical  return used is NOT
the Fund's actual return -- the results do not apply to your  investment and you
cannot use the  hypothetical  account  value and expense to estimate  the actual
ending  account  balance or expenses  you paid for the period.  This  example is
useful in making  comparisons  of the ongoing costs of investing in the Fund and
other  funds.  To do so,  compare  this  5%  hypothetical  example  with  the 5%
hypothetical examples that appear in shareholder reports of other funds.

Please note that the  expenses  shown in the table are meant to  highlight  your
ongoing  costs only and do not  reflect  any  transactional  costs such as sales
charges (loads),  redemption fees, or exchange fees, if any, which are described
in the Prospectus. If these costs were applied to your account, your costs would
be higher.  Therefore, the 5% hypothetical return is useful in comparing ongoing
costs only,  and will not help you determine the relative  total costs of owning
different funds. The "Annualized  Expense Ratio"  represents the actual expenses
for the last six  months  and may be  different  from the  expense  ratio in the
Financial Highlights which is for the six months ended June 30, 2005.

                    Beginning        Ending     Annualized    Expenses
                  Account Value   Account Value   Expense    Paid During
                    01/01/05        06/30/05       Ratio       Period*
- --------------------------------------------------------------------------------
THE GABELLI MATHERS FUND
- --------------------------------------------------------------------------------
ACTUAL FUND RETURN
Gabelli Mathers    $1,000.00        $1,006.70       2.08%     $10.35

HYPOTHETICAL 5% RETURN
Gabelli Mathers    $1,000.00        $1,014.48       2.08%     $10.39

*  Expenses are equal to the Fund's  annualized  expense  ratio for the last six
   months multiplied by the average account value over the period, multiplied by
   the number of days in the most recent fiscal half-year, then divided by 365.

                                        2



SUMMARY OF PORTFOLIO HOLDINGS (UNAUDITED)

The  following  tables  present  portfolio  holdings  as a percent  of total net
assets.

THE GABELLI MATHERS FUND -
   LONG POSITIONS                                    PERCENT

U.S. Government Obligations .......................  89.5%
Repurchase Agreements .............................   3.6%
Computer Software and Services ....................   1.4%
Health Care .......................................   1.4%
Environmental Services ............................   0.7%
Financial Services ................................   0.7%
Metals and Mining .................................   0.7%
Telecommunications ................................   0.6%
Broadcasting ......................................   0.5%
Energy and Utilities ..............................   0.4%
Equipment .........................................   0.2%
Food and Beverage .................................   0.2%
Transportation ....................................   0.1%
Aerospace .........................................   0.1%
Entertainment .....................................   0.1%

THE GABELLI MATHERS FUND -
   SHORT POSITIONS                                   PERCENT

Exchange Traded Funds .............................  (9.0)%
Equipment .........................................  (4.3)%
Retail ............................................  (3.4)%
Consumer Products .................................  (2.8)%
Restaurants .......................................  (1.5)%
Financial Services ................................  (0.9)%
Diversified Industrial ............................  (0.7)%
Home Furnishings ..................................  (0.7)%
Automotive ........................................  (0.6)%
Entertainment .....................................  (0.4)%


THE FUND FILES A COMPLETE  SCHEDULE OF PORTFOLIO  HOLDINGS  WITH THE SEC FOR THE
FIRST AND THIRD  QUARTERS OF EACH FISCAL YEAR ON FORM N-Q, THE LAST OF WHICH WAS
FILED FOR THE  QUARTER  ENDING  MARCH 31,  2005.  SHAREHOLDERS  MAY OBTAIN  THIS
INFORMATION   AT   WWW.GABELLI.COM   OR  BY  CALLING  THE  FUND  AT  800-GABELLI
(800-422-3554).  THE  FUND'S  FORM N-Q IS  AVAILABLE  ON THE  SEC'S  WEBSITE  AT
WWW.SEC.GOV  AND MAY ALSO BE  REVIEWED  AND  COPIED AT THE  COMMISSION'S  PUBLIC
REFERENCE  ROOM IN  WASHINGTON,  DC.  INFORMATION ON THE OPERATION OF THE PUBLIC
REFERENCE ROOM MAY BE OBTAINED BY CALLING 1-800-SEC-0330.


PROXY VOTING

The Fund files Form N-PX with its complete proxy voting record for the 12 months
ended June 30th,  no later than August 31st of each year. A  description  of the
Fund's proxy voting policies and procedures are available  without charge,  upon
request,  (i) by  calling  800-GABELLI  (800-422-3554);  (ii) by  writing to The
Gabelli Funds at One Corporate Center, Rye, NY 10580-1422; and (iii) by visiting
the Securities and Exchange Commission's website at www.sec.gov.




                                        3



THE GABELLI MATHERS FUND
SCHEDULE OF INVESTMENTS -- JUNE 30, 2005 (UNAUDITED)
- --------------------------------------------------------------------------------

                                                               MARKET
     SHARES                                    COST            VALUE
     ------                                    ----            -----

             COMMON STOCKS -- 7.1%
             AEROSPACE -- 0.1%
      1,000  Titan Corp.+ ..............  $    22,420      $   22,740
                                          -----------     -----------
             BROADCASTING -- 0.5%
      4,000  Liberty Global Inc., Cl. A+      142,331         186,680
                                          -----------     -----------
             COMPUTER SOFTWARE AND SERVICES -- 1.4%
      9,000  CACI International Inc.,
               Cl. A+ ..................      482,400         568,440
                                          -----------     -----------
             ENERGY AND UTILITIES -- 0.4%
        500  Cinergy Corp. .............       18,045          22,410
      1,000  Duquesne Light
               Holdings Inc. ...........       15,295          18,680
      3,000  Veolia Environnement, ADR..      101,550         112,200
                                          -----------     -----------
                                              134,890         153,290
                                          -----------     -----------
             ENTERTAINMENT -- 0.1%
      6,000  Gemstar-TV Guide
               International Inc.+ .....       35,273          21,540
                                          -----------     -----------
             ENVIRONMENTAL SERVICES -- 0.7%
     10,000  Waste Management Inc. .....      291,362         283,400
                                          -----------     -----------
             EQUIPMENT -- 0.2%
      5,000  Ultratech Inc.+ ...........       79,836          91,500
                                          -----------     -----------
             FINANCIAL SERVICES -- 0.7%
     15,000  New York Community
               Bancorp Inc. ............      274,039         271,800
                                          -----------     -----------
             FOOD AND BEVERAGE -- 0.2%
      4,000  Hain Celestial Group Inc.+        68,261          78,000
                                          -----------     -----------
             HEALTH CARE -- 1.4%
      1,500  Abbott Laboratories .......       69,119          73,515
      8,000  Baxter International Inc...      265,459         296,800
      2,000  Eon Labs Inc.+ ............       61,260          61,280
      2,000  Guidant Corp. .............      125,000         134,600
                                          -----------     -----------
                                              520,838         566,195
                                          -----------     -----------
             METALS AND MINING -- 0.7%
     40,000  AK Steel Holding Corp.+ ...      312,828         256,400
                                          -----------     -----------
             TELECOMMUNICATIONS -- 0.6%
      7,142  ADC
               Telecommunications Inc.+       133,533         155,481
      1,000  BellSouth Corp. ...........       24,080          26,570
      1,000  SBC Communications Inc. ...       22,310          23,750
      1,000  Verizon
               Communications Inc. .....       32,920          34,550
                                          -----------     -----------
                                              212,843         240,351
                                          -----------     -----------
             TRANSPORTATION -- 0.1%
      1,000  Overnite Corp. ............       42,980          42,980
                                          -----------     -----------
             TOTAL COMMON STOCKS .......    2,620,301       2,783,316
                                          -----------     -----------

  PRINCIPAL                                                   MARKET
    AMOUNT                                    COST             VALUE
  ---------                                   ----             -----
             SHORT-TERM OBLIGATIONS -- 93.1%
             REPURCHASE AGREEMENTS -- 3.6%
$ 1,406,905  State Street Bank & Trust Co.,
               2.720%, dated 06/30/05,
               due 07/01/05, proceeds at
               maturity, $1,407,011 (b)   $ 1,406,905     $ 1,406,905
                                          -----------     -----------
             U.S. GOVERNMENT  OBLIGATIONS -- 89.5%
 35,000,000  U.S. Treasury Bill,
               2.791%++, 07/07/05 (a) ..   34,983,958      34,983,958
                                          -----------     -----------
             TOTAL SHORT-TERM
               OBLIGATIONS .............   36,390,863      36,390,863
                                          -----------     -----------
             TOTAL
               INVESTMENTS -- 100.2% ...  $39,011,164      39,174,179
                                          ===========
             OTHER ASSETS AND LIABILITIES (NET) -- (0.2)%     (94,026)
                                                          -----------
             NET ASSETS -- 100.0% ...................     $39,080,153
                                                          ===========
             SECURITIES SOLD SHORT -- (24.3)%

                                                               MARKET
     SHARES                                  PROCEEDS          VALUE
     ------                                  --------          -----

             COMMON STOCKS -- (24.3)%
             AUTOMOTIVE -- (0.6)%
     24,000  Ford Motor Co. ............  $   301,071     $   245,760
                                          -----------     -----------
             CONSUMER PRODUCTS -- (2.8)%
      6,000  Harley-Davidson Inc. ......      348,694         297,600
     15,000  Polaris Industries Inc. ...      721,408         810,000
                                          -----------     -----------
                                            1,070,102       1,107,600
                                          -----------     -----------
             DIVERSIFIED INDUSTRIAL -- (0.7)%
      8,000  Briggs & Stratton Corp. ...      261,580         276,960
                                          -----------     -----------
             ENTERTAINMENT -- (0.4)%
      3,000  Carnival Corp. ............      137,442         163,650
                                          -----------     -----------
             EQUIPMENT -- (4.3)%
     15,000  Black & Decker Corp. ......    1,194,494       1,347,750
      8,000  Toro Co. ..................      306,987         308,880
                                          -----------     -----------
                                            1,501,481       1,656,630
                                          -----------     -----------
             EXCHANGE TRADED FUNDS -- (9.0)%
     24,000  iShares S&P Smallcap
               600 Index ...............    1,216,296       1,320,480
      8,000  Midcap SPDR Trust,
               Series 1 ................      926,841       1,002,000
     10,000  Standard & Poor's
               Depository Receipts .....    1,156,576       1,191,800
                                          -----------     -----------
                                            3,299,713       3,514,280
                                          -----------     -----------

                 See accompanying notes to financial statements.

                                        4


THE GABELLI MATHERS FUND
SCHEDULE OF INVESTMENTS (CONTINUED) -- JUNE 30, 2005 (UNAUDITED)
- --------------------------------------------------------------------------------

                                                               MARKET
     SHARES                                  PROCEEDS          VALUE
     ------                                  --------          -----

             SECURITIES SOLD SHORT (CONTINUED)
             COMMON STOCKS (CONTINUED)
             FINANCIAL SERVICES -- (0.9)%
     12,000  Morningstar Inc. ..........  $   280,962      $  337,800
                                          -----------     -----------
             HOME FURNISHINGS -- (0.7)%
      4,000  Ethan Allen Interiors Inc.       157,125         134,040
      9,000  La-Z-Boy Inc. .............      187,298         131,130
                                          -----------     -----------
                                              344,423         265,170
                                          -----------     -----------
             RESTAURANTS -- (1.5)%
      7,000  Cheesecake Factory Inc. ...      179,921         243,110
      5,000  McDonald's Corp. ..........      125,858         138,750
      4,000  Starbucks Corp. ...........      213,283         206,640
                                          -----------     -----------
                                              519,062         588,500
                                          -----------     -----------
             RETAIL -- (3.4)%
      3,000  Kohl's Corp. ..............      142,902         167,730
      5,000  The Home Depot Inc. .......      161,867         194,500
     15,000  Tiffany & Co. .............      443,496         491,400
     15,000  Zale Corp. ................      427,593         475,350
                                          -----------     -----------
                                            1,175,858       1,328,980
                                          -----------     -----------
             TOTAL SECURITIES
               SOLD SHORT                 $ 8,891,694     $ 9,485,330
                                          ===========     ===========
- ----------------
(a)  At June 30,  2005,  $25,000,000  of the  principal  amount  was  pledged as
     collateral for securities sold short.
(b)  Collateralized  by U.S.  Treasury Bond,  8.00%, due 11/15/21,  market value
     $1,447,725.
+    Non-income producing security.
++   Represents annualized yield at date of purchase.
ADR  American Depository Receipt
SPDR Standard & Poor's Depository Receipts


                 See accompanying notes to financial statements.

                                        5


                            THE GABELLI MATHERS FUND

STATEMENT OF ASSETS AND LIABILITIES
JUNE 30, 2005 (UNAUDITED)
- --------------------------------------------------------------------------------

ASSETS:
  Investments, at value (Cost $39,011,164) ..........    $ 39,174,179
  Deposit at brokers ................................         692,703
  Dividends and interest receivable .................           7,184
  Receivable for investments sold ...................       8,891,694
  Other assets ......................................           1,691
                                                         ------------
  TOTAL ASSETS ......................................      48,767,451
                                                         ------------
LIABILITIES:
  Securities sold short (proceeds $8,891,694) .......       9,485,330
  Payable for investments purchased .................         104,240
  Dividends payable on securities sold short ........          10,449
  Payable for investment advisory fees ..............          32,373
  Payable for distribution fees .....................           8,093
  Other accrued expenses and liabilities ............          46,813
                                                         ------------
  TOTAL LIABILITIES .................................       9,687,298
                                                         ------------
  NET ASSETS applicable to 3,700,496
    shares outstanding ..............................    $ 39,080,153
                                                         ============
NET ASSETS CONSIST OF:
  Shares of beneficial interest,
    at $0.001 par value .............................    $      3,700
  Additional paid-in capital ........................      60,294,652
  Accumulated net investment income .................         128,073
  Accumulated net realized loss on investments
    and securities sold short .......................     (20,915,651)
  Net unrealized depreciation on securities
    sold short ......................................        (593,636)
  Net unrealized appreciation on investments ........         163,015
                                                         ------------
  NET ASSETS ........................................    $ 39,080,153
                                                         ============
  NET ASSET VALUE, offering and redemption price
    per share ($39,080,153 / 3,700,496 shares
    outstanding; unlimited number of shares
    authorized of $0.001 par value) .................          $10.56
                                                               ======

STATEMENT OF OPERATIONS
FOR THE SIX MONTHS ENDED JUNE 30, 2005 (UNAUDITED)
- --------------------------------------------------------------------------------

INVESTMENT INCOME:
  Dividends (net of foreign taxes of $373) ..........      $  16,972
  Interest ..........................................        446,042
  Other income ......................................         79,027
                                                           ---------
  TOTAL INVESTMENT INCOME ...........................        542,041
                                                           ---------
EXPENSES:
  Investment advisory fees ..........................        199,198
  Distribution fees .................................         49,800
  Dividends on securities sold short ................         45,380
  Trustees' fees ....................................         28,137
  Shareholder services fees .........................         24,321
  Shareholder communications expenses ...............         19,832
  Legal and audit fees ..............................         17,354
  Custodian fees ....................................         16,316
  Registration fees .................................          8,418
  Miscellaneous expenses ............................          5,288
                                                           ---------
  TOTAL EXPENSES ....................................        414,044
  Less: Custodian fee credits .......................            (76)
                                                           ---------
  TOTAL NET EXPENSES ................................        413,968
                                                           ---------
  NET INVESTMENT INCOME .............................        128,073
                                                           ---------
NET REALIZED AND UNREALIZED GAIN (LOSS) ON
  INVESTMENTS AND SECURITIES SOLD SHORT:
  Net realized gain on investments ..................        415,050
  Net realized loss on securities sold short ........        (84,799)
  Net change in unrealized appreciation/depreciation
    on investments and securities sold short ........       (184,192)
                                                           ---------
  NET REALIZED AND UNREALIZED GAIN (LOSS) ON
    INVESTMENTS AND SECURITIES SOLD SHORT ...........        146,059
                                                           ---------
  NET INCREASE IN NET ASSETS RESULTING
    FROM OPERATIONS .................................      $ 274,132
                                                           =========

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


                                                                                           SIX MONTHS ENDED
                                                                                             JUNE 30, 2005      YEAR ENDED
                                                                                              (UNAUDITED)    DECEMBER 31, 2004
                                                                                           ----------------  -----------------

                                                                                                               
OPERATIONS:
  Net investment income (loss) ............................................................     $  128,073      $  (292,952)
  Net realized gain on investments ........................................................        415,050          300,236
  Net realized loss on securities sold short ..............................................        (84,799)        (575,794)
  Net change in unrealized appreciation/depreciation on investments and securities sold short     (184,192)           1,130
                                                                                               -----------     ------------
  NET INCREASE (DECREASE) IN NET ASSETS RESULTING FROM OPERATIONS .........................        274,132         (567,380)
                                                                                               -----------     ------------
SHARES OF BENEFICIAL INTEREST TRANSACTIONS:
  Net decrease in net assets from shares of beneficial interest transactions ..............     (2,451,844)     (19,020,306)
                                                                                               -----------     ------------
  REDEMPTION FEES .........................................................................             26               --
                                                                                               -----------     ------------
  NET DECREASE IN NET ASSETS ..............................................................     (2,177,686)     (19,587,686)
NET ASSETS:
  Beginning of period .....................................................................     41,257,839       60,845,525
                                                                                               -----------     ------------
  End of period (including undistributed net investment income of
    $128,073 and $0, respectively) ........................................................    $39,080,153     $ 41,257,839
                                                                                               ===========     ============



                 See accompanying notes to financial statements.

                                       6



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 of the foreign markets, but prior to the close of business on
the day the securities are being valued, 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 amount 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 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.


                                       7



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------


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 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, 2005, 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 the 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, 2005 are reflected in the Schedule 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.

EXPENSES.  Certain  administrative  expenses are common to, and allocated among,
various  affiliated funds. Such allocations are made on the basis of each Fund's
average  net  assets  or other  criteria  directly  affecting  the  expenses  as
determined by the Adviser pursuant to procedures established by the Board.


                                       8



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------


DIVIDENDS AND  DISTRIBUTIONS  TO  SHAREHOLDERS.  Dividends and  distributions to
shareholders are recorded on the ex-dividend date. Distributions to shareholders
are based on  ordinary  income and  long-term  capital  gains as  determined  in
accordance with Federal income tax regulations, which may differ from income and
capital gains as determined under U.S. generally accepted accounting principles.
These differences are primarily due to differing  treatments of income and gains
on  various  investment  securities  held by the Fund,  timing  differences  and
differing characterizations of distributions made by the Fund.

No distributions  were made in the six months ended June 30, 2005 and the fiscal
year ended December 31, 2004.

These book/tax  differences are either temporary or permanent in nature.  To the
extent these differences are permanent,  adjustments are made to the appropriate
equity accounts in the period that the differences arise.

For the year ended  December 31, 2004,  reclassifications  were made to decrease
accumulated  net  investment  loss by $292,952 and to decrease  accumulated  net
realized loss on investments by  $22,226,886,  with an offsetting  adjustment to
additional paid-in capital.  These  reclassifications  have no impact on the net
asset value of the Fund and the  calculation of net investment  income per share
in the financial highlights excludes these adjustments.

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").  It is the policy of the Fund to comply with the
requirements  of the Code  applicable to regulated  investment  companies and to
distribute  substantially  all of its net investment  company taxable income and
net capital gains. Therefore, no provision for Federal income taxes is required.

As of December 31, 2004, the components of earnings/(losses) on a tax basis were
as follows:

       Capital loss carryforward ................................ $(21,245,902)
       Net unrealized appreciation/(depreciation) of investments       515,810
       Net unrealized appreciation/(depreciation) of securities
         sold short .............................................     (762,239)
                                                                  ------------
       Total accumulated loss ................................... $(21,492,331)
                                                                  ============

The Fund has a net capital loss  carryforward for Federal income tax purposes at
December 31, 2004 of $21,245,902. This capital loss carryforward is available to
reduce  future  required  distributions  of net capital  gains to  shareholders.
$22,226,886 of the loss  carryforward  expired in 2004;  $7,869,968 is available
through  2006;  $12,430,175  is available  through  2010;  $670,201 is available
through 2011; and $275,558 is available through 2012.

The following  summarizes the tax cost of  investments,  proceeds of short sales
and related unrealized appreciation (depreciation) at June 30, 2005:


                                                   GROSS           GROSS       NET UNREALIZED
                                                UNREALIZED      UNREALIZED      APPRECIATION/
                               COST/PROCEEDS   APPRECIATION    DEPRECIATION    (DEPRECIATION)
                               -------------   ------------    ------------    --------------
                                                                     
      Investments ............  $39,011,164      $243,377       $ (80,362)       $ 163,015
      Short sales ............    8,891,694       192,301        (785,937)        (593,636)
                                                 --------       ---------        ---------
                                                 $435,678       $(866,299)       $(430,621)
                                                 ========       =========        =========


                                       9



THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------


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 its  average  daily 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 the Adviser's affiliates.

4.  DISTRIBUTION  PLAN.  The Fund's Board has adopted a  distribution  plan (the
"Plan") pursuant to Rule 12b-1 under the 1940 Act. For the six months ended June
30, 2005,  the Fund  incurred  distribution  costs payable to Gabelli & Company,
Inc.,  an affiliate of the Adviser,  of $49,800,  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, 2005, other than short term securities, aggregated
$1,323,311 and $1,776,163, respectively.

6. TRANSACTIONS WITH AFFILIATES.  During the six months ended June 30, 2005, the
Fund paid brokerage commissions of $7,655 to Gabelli & Company, Inc.

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

 


                                               SIX MONTHS ENDED
                                                 JUNE 30, 2005                      YEAR ENDED
                                                  (UNAUDITED)                    DECEMBER 31, 2004
                                           ------------------------      ----------------------------
                                            SHARES          AMOUNT           SHARES           AMOUNT
                                           --------        --------        --------          --------
                                                                               
Shares sold ..............................   31,242     $   329,845         239,007      $  2,532,625
Shares redeemed .......................... (264,549)     (2,781,689)     (2,043,820)      (21,552,931)
                                           --------     -----------      ----------      ------------
  Net decrease ........................... (233,307)    $(2,451,844)     (1,804,813)     $(19,020,306)
                                           ========     ===========      ==========      ============


Effective  June 15, 2005,  the Fund imposed a redemption  fee of 2.00% on shares
that are  redeemed or exchanged on or before the seventh day after the date of a
purchase.  (Prior to June 15, 2005,  the Fund imposed a redemption fee on shares
that were  redeemed or  exchanged  within the  sixtieth  day after the date of a
purchase.) The redemption fee is deducted from the proceeds otherwise payable to
the redeeming shareholders and is retained by the Fund.

The redemption fee does not apply to shares purchased  through programs that the
Adviser  determined to have  appropriate  short-term  trading policies in place.
Additionally,  certain recordkeepers for qualified and non-qualified  retirement
plans that could not collect the redemption fee at the participant  level due to
systems limitations have received an extension to implement such systems.

8. OTHER MATTERS. The Adviser and/or affiliates have received subpoenas from the
Attorney General of the State of New York and the SEC requesting  information on
mutual fund  shares  trading  practices.  Gabelli  Asset  Management  Inc.,  the
Adviser's  parent  company,  is responding  to these  requests for documents and
testimony.  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


THE GABELLI MATHERS FUND
NOTES TO FINANCIAL STATEMENTS (CONTINUED) (UNAUDITED)
- --------------------------------------------------------------------------------


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



                                          SIX MONTHS ENDED                          YEAR ENDED DECEMBER 31,
                                            JUNE 30, 2005       -----------------------------------------------------------
                                             (UNAUDITED)          2004         2003         2002         2001         2000
                                          ----------------       ------       ------       ------       ------       ------

                                                                                                  
OPERATING PERFORMANCE:
   Net asset value, beginning of period ..... $ 10.49           $ 10.60      $ 10.81      $ 12.25      $ 12.05      $ 11.94
                                              -------           -------      -------      -------      -------      -------
   Net investment income (loss) .............    0.03             (0.06)       (0.07)       (0.00)(a)     0.30         0.49
   Net realized and unrealized
     gain (loss) on investments .............    0.04             (0.05)       (0.14)       (1.44)        0.21         0.11
                                              -------           -------      -------      -------      -------      -------
   Total from investment operations .........    0.07             (0.11)       (0.21)       (1.44)        0.51         0.60
                                              -------           -------      -------      -------      -------      -------
DISTRIBUTIONS TO SHAREHOLDERS:
   Net investment income ....................      --                --           --           --        (0.31)       (0.49)
                                              -------           -------      -------      -------      -------      -------
   Total distributions ......................      --                --           --           --        (0.31)       (0.49)
                                              -------           -------      -------      -------      -------      -------
REDEMPTION FEES .............................    0.00(a)             --           --           --           --           --
                                              -------           -------      -------      -------      -------      -------
   NET ASSET VALUE, END OF PERIOD ........... $ 10.56           $ 10.49     $  10.60      $ 10.81      $ 12.25      $ 12.05
                                              =======           =======     ========      =======      =======      =======
   Total return+ ............................   0.67%           (1.04)%      (1.94)%     (11.76)%        4.25%        5.02%
                                              =======           =======     ========      =======      =======      =======
RATIOS TO AVERAGE NET ASSETS
   AND SUPPLEMENTAL DATA:
   Net assets, end of period (in 000's) .....  $39,080          $41,258      $60,846      $80,827      $97,893      $99,855
   Ratio of net investment income
     to average net assets ..................    0.64%(b)       (0.61)%      (0.61)%      (0.00)%        2.45%        3.79%
   Ratio of operating expenses
     to average net assets (c) ..............    2.08%(b)         1.77%        1.67%        1.63%        1.35%        1.34%
   Ratio of operating expenses to average
     net assets excluding the effect of
     dividends on securities sold short (c)..    1.85%(b)         1.64%        1.64%        1.61%        1.33%        1.30%
   Portfolio turnover rate ..................      39%             176%         244%         776%        1013%         977%

- ----------
  + 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) Amount is less than $0.005 per share.
(b) Annualized.
(c) The ratios do not include a reduction of expenses for  custodian fee credits
    on cash balances  maintained  with the  custodian.
    For the six months ended June 30, 2005, the effect of the custodian fee
    credits was minimal.

                 See accompanying notes to financial statements.

                                       11


                            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
   EXECUTIVE OFFICER                            PROFESSOR EMERITUS,
   GABELLI ASSET MANAGEMENT INC.                PACE UNIVERSITY

   E. Val Cerutti                               Werner J. Roeder, MD
   CHIEF EXECUTIVE OFFICER                      MEDICAL DIRECTOR
   CERUTTI CONSULTANTS, INC.                    LAWRENCE HOSPITAL

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

   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
                                                Heidi M. Koontz
   Bruce N. Alpert                              VICE PRESIDENT
   EXECUTIVE VICE PRESIDENT
   AND TREASURER                                Edith L. Cook
                                                VICE PRESIDENT
   James E. McKee
   VICE PRESIDENT                               Peter D. Goldstein
   AND SECRETARY                                CHIEF COMPLIANCE OFFICER

                                   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.
- --------------------------------------------------------------------------------
GAB1726Q205SR



                                                                [GRAPHIC OMITED]
                                                                Mario J. Gabelli

THE
GABELLI
MATHERS
FUND


                                                              SEMI-ANNUAL REPORT
                                                                   JUNE 30, 2005


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

Schedule of Investments in securities of unaffiliated issuers as of the close of
the  reporting  period is included as part of the report to  shareholders  filed
under Item 1 of this form.



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

Not applicable.



ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

Not applicable.


ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT
        COMPANY AND AFFILIATED PURCHASERS.

Not applicable.



ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

There have been no material  changes to the procedures by which the shareholders
may  recommend  nominees to the  registrant's  Board of  Directors,  where those
changes were  implemented  after the  registrant  last  provided  disclosure  in
response to the  requirements  of Item  7(d)(2)(ii)(G)  of Schedule  14A (17 CFR
240.14a-101), or this Item.


ITEM 11. 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  second
          fiscal  quarter  of  the  period  covered  by  this  report  that  has
          materially affected, or is reasonably likely to materially affect, the
          registrant's internal control over financial reporting.


ITEM 12. 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(b)  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/ Henry G. Van der Eb
                         -------------------------------------------------------
                           Henry G. Van der Eb, Chief Executive Officer


Date     September 7, 2005
    ----------------------------------------------------------------------------


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/ Henry G. Van der Eb
                         -------------------------------------------------------
                           Henry G. Van der Eb, Chief Executive Officer


Date     September 7, 2005
    ----------------------------------------------------------------------------


By (Signature and Title)*  /s/ Bruce N. Alpert
                         -------------------------------------------------------
                           Bruce N. Alpert, Treasurer &
                           Principal Financial Officer


Date     September 7, 2005
    ----------------------------------------------------------------------------



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