U.S. SECURITIES AND EXCHANGE
                             COMMISSION WASHINGTON,
                                   D.C. 20549
                                   FORM U-9C-3



                     QUARTERLY REPORT PURSUANT TO RULE 58 OF
                 THE PUBLIC UTILITY HOLDING COMPANY ACT OF 1935

                For the quarterly period ended December 31, 2003
                                               -----------------



                      FirstEnergy Corp. (File No. 70-09501)
                   -------------------------------------------
                      (Name of Registered Holding Company)


                     76 South Main Street, Akron, Ohio 44308
                   -------------------------------------------
                    (Address of Principal Executive Offices)








                                FirstEnergy Corp.


                     Quarterly Report Pursuant to Rule 58 of
                 the Public Utility Holding Company Act of 1935

                For the quarterly period ended December 31, 2003
                                               ------------------



                                 Table of Contents
                                 -----------------

  Item
   No.                                 Title                            Page
  -----          ----------------------------------------------         ----
     1           Organization Chart                                      1-4

     2           Issuances and Renewals of Securities and
                 Capital Contributions                                     5

     3           Associate Transactions                                  6-8

     4           Summary of Aggregate Investment                           9

     5           Other Investments                                        10

     6           Financial Statements and Exhibits:

                     A - Financial Statements                          11-12

                     B - Exhibits                                         13

                     C - Certificate of FirstEnergy Corp.                 13

                 Signature                                                14


  Note:      All dollar amounts shown in this Form U-9C-3 are expressed in
  ----       thousands unless otherwise noted.






                                                    ITEM 1 - ORGANIZATION CHART


                                                         Energy (ERC)
                                                         or Gas (GRC)     Date of       State of    Percentage of Voting   Nature of
            Name of Reporting Company                  Related Company  Organization  Organization    Securities Held      Business
------------------------------------------------       ---------------  ------------  ------------  -------------------    ---------

FirstEnergy Corp. (a)

                                                                                                               
    FirstEnergy Ventures Corp. (b)
       Bay Shore Power Company (d)                            ERC         01/26/1998     Ohio              100.0              (h)
       Centerior Energy Services, Inc. (d)                    ERC         06/01/1994     Ohio              100.0              (i)
       Eastroc Technologies, LLC (c)                          ERC         04/30/1996     Delaware           50.0 **           (j)
       Engineered Processes, Ltd. (c)                         ERC         12/30/1996     Ohio               50.0 **           (j)
       Warrenton River Terminal, Ltd. (d)                     ERC         09/03/1996     Ohio              100.0              (k)

    FirstEnergy Facilities Services Group, LLC (b)
       Dunbar Mechanical, Inc. (e)                            ERC         07/16/1956     Ohio              100.0              (g)
       Edwards Electrical & Mechanical, Inc. (e)              ERC         02/28/1968     Indiana           100.0              (g)
       Elliot-Lewis Corporation (e)                           ERC         05/21/1998     Pennsylvania      100.0              (g)
        A.A. Duckett, Inc.                                    ERC         03/01/1973     Delaware          100.0              (g)
        Sautter Crane Rental, Inc.                            ERC         12/10/1991     Pennsylvania      100.0              (l)
        E-L Enterprises, Inc.
          Modern Air Conditioning, Inc.                       ERC         04/27/1965     Florida           100.0              (g)
            Airdex Air Conditioning Corporation               ERC         01/18/1995     Florida           100.0              (g)
          R.L. Anderson, Inc.                                 ERC         08/28/1961     Florida           100.0              (g)
       L.H. Cranston and Sons, Inc. (e)                       ERC         01/02/1951     Maryland          100.0              (g)
       Roth Bros., Inc. (e)                                   ERC         09/06/1947     Ohio              100.0              (g)
       The Hattenbach Company (e)                             ERC         03/21/1969     Ohio              100.0              (m)
       R.P.C. Mechanical, Inc. (e)                            ERC         04/21/1959     Ohio              100.0              (g)
       Spectrum Controls Systems, Inc. (e)                    ERC         04/18/1988     Ohio              100.0              (g)

    FirstEnergy Solutions Corp. (b)                           ERC         08/08/1997     Ohio              100.0              (n)
       FirstEnergy Engineering, Inc. (f)                      ERC         08/09/1996     Ohio              100.0              (u)

    GPU Diversified Holdings, LLC (GPUDH) (b)                             08/03/2000     Delaware          100.0              (s)
       GPU Solar, Inc.                                        ERC         11/07/1997     New Jersey         50.0 **           (t)
       GPU Distributed Power, Inc. *                          ERC         02/29/2000     Delaware          100.0
       Active Power, Inc.                                     ERC                                          0.006 **           (r)
       Ballard Power Systems Inc.                             ERC                                                             (w)
       EnviroTech Investment Fund I, LP                       ERC                                            9.9 **           (v)
       EnerTech Capital Partners II, LP                       ERC                                            2.0 **           (v)


*  Inactive
** Set forth the percentage of interest held directly or indirectly by FirstEnergy Corp.

                                                                   1






                                                                 ITEM 1 - ORGANIZATION CHART (Continued)

                                                         Energy (ERC)
                                                         or Gas (GRC)     Date of       State of    Percentage of Voting   Nature of
            Name of Reporting Company                  Related Company  Organization  Organization    Securities Held      Business
------------------------------------------------       ---------------  ------------  ------------  -------------------    ---------

FirstEnergy Corp. (a) (Continued)

                                                                                                               
    Ohio Edison Company (OE)
       EnviroTech Investment Fund I, LP                       ERC                                            6.0 **           (v)

    PowerSpan Corp. (c)                                       ERC         05/01/1997     Delaware          18.63 **           (0)

    Kinetic Ventures I, LLC (c)                               ERC         04/15/1997     Delaware          11.11 **           (p)

    Kinetic Ventures II, LLC (c)                              ERC         12/07/1999     Delaware          14.28 **           (p)

    Nth Power Technologies II, LLC (c)                        ERC                                            8.2 **           (q)

    Utility.com, Inc. (c) *                                   ERC                                            5.0 **           (n)

    Automated Power Exchange, Inc. (c)                        ERC                                           1.16 **           (n)


*  Inactive
** Set forth the percentage of interest held directly or indirectly by FirstEnergy Corp.


                                                                   2





                     ITEM 1 - ORGANIZATION CHART (Continued)

(a)  FirstEnergy Corp., a registered holding company,  holds securities directly
     or indirectly in the energy-related companies set below its name.
(b)  These companies are direct wholly owned subsidiaries of FirstEnergy Corp.
(c)  FirstEnergy  Corp.  owns  an  interest  directly  or  indirectly  in  these
     energy-related companies or venture capital funds set below its name.
(d)  These  companies  are  direct  wholly  owned  subsidiaries  of  FirstEnergy
     Ventures Corp.
(e)  These  companies  are  direct  wholly  owned  subsidiaries  of  FirstEnergy
     Facilities Services Group, LLC.
(f)  This company is direct  wholly owned  subsidiary of  FirstEnergy  Solutions
     Corp.
(g)  This  subsidiary   provides  HVAC  equipment   installation  and  services,
     facilities management, and energy management.
(h)  This subsidiary  owns and operates a petroleum coke disposal  facility that
     will  supply  steam  for  the  Bay  Shore  Power  Plant  and  to  BP  Amoco
     Corporation.
(i)  This subsidiary  provides  various  consulting  services  related to energy
     management and procurement.
(j)  This subsidiary  holds the patent on plaster,  which is manufactured  using
     the by-Products of coal-fired generation facilities.
(k)  This  subsidiary  owns  facilities for the  transloading  of bulk materials
     (primarily  coal)  on the  Ohio  River.  The  coal is in  part  used by the
     FirstEnergy Operating Companies at various generation facilities.
(l)  This subsidiary provides crane rental services.
(m)  This  subsidiary  provides  refrigeration  sales and services to commercial
     entities.
(n)  This   subsidiary   engages  in  the  brokering  and  marketing  of  energy
     commodities.
(o)  This company was formed to utilized advanced technology to reduce emissions
     of NOx, SO2 and particulate matter from utility generation facilities.
(p)  This  venture  capital fund is focus on early stage  companies  involved in
     energy-related  fields and  technology.
(q)  This venture  capital fund is focus on emerging  technologies in the global
     energy industry.
(r)  This company is a developer of flywheel  energy  storage  system for use in
     uninterruptible power supply and other power quality applications.
(s)  This energy-related company holds securities directly in the energy-related
     company  set  below  its  name.
(t)  This  subsidiary is involved in the development  and  commercialization  of
     photovoltaics.
(u)  This subsidiary provides engineering services.
(v)  An investment fund which invests in energy-related technology. GPUDH owns a
     9.89% interest and OE owns a 6% interest.
(w)  GPU Diversified Holdings LLC owns 1,366,062 shares of Ballard Power Systems
     Inc. (BPS) common stocks. BPS develop stationary fuel cell systems.

                                        3




                     ITEM 1 - ORGANIZATION CHART (Continued)


            Narrative Description of Activities for Reporting Period
            --------------------------------------------------------

The Alliance Participants Administrative and Startup Activities Company, LLC was
dissolved on October 31, 2003.


Ancoma, Inc. was sold on December 29, 2003.

                                        4





                                ITEM 2 - ISSUANCES AND RENEWALS OF SECURITIES AND CAPITAL CONTRIBUTIONS

                             Type of        Principal                              Company to       Collateral      Consideration
                             Security       Amount of     Issue or    Cost of     whom Security     Given with         Received
Company Issuing Security     Issued         Security      Renewal     Capital      was Issued        Security     for Each Security
------------------------   -----------   -------------    --------    -------     -------------     -----------   -----------------

                                                                                             
         None.






 Company Contributing           Company Receiving            Amount of Capital
        Capital                      Capital                   Contribution
 ---------------------     ----------------------------      ----------------

 FirstEnergy Corp.         GPU Diversified Holdings LLC          $  400

 FirstEnergy Corp.               PowerSpan Corp.                 $  984



Note:   The information provided in Item 2 presents the activities of the
----    reporting period only.

                                        5





                                                    ITEM 3 - ASSOCIATE TRANSACTIONS


Part I - Transactions Performed by Reporting Companies on Behalf of Associate Companies



                                                                                                                     Total
                                                                                                                     Amount
Reporting Company Rendering Services     Associate Company Receiving Services       Types of Services Rendered       Billed
------------------------------------     ------------------------------------       --------------------------       ------

                                                                              
Bay Shore Power Company                  FirstEnergy Generation Corp.               Sale of steam

Centerior Energy Services, Inc.          FirstEnergy Solutions Corp.                Energy consulting services

Dunbar Mechanical, Inc.                  FirstEnergy Generation Corp.               HVAC services

Dunbar Mechanical, Inc.                  FirstEnergy Nuclear Operating Company      HVAC services

Dunbar Mechanical, Inc.                  FirstEnergy Solutions Corp.                HVAC services

Elliot-Lewis Corporation                 FirstEnergy Solutions Corp.                HVAC services

FirstEnergy Solutions Corp.              FirstEnergy Generation Corp.               Natural gas procurement &
                                                                                    scheduling services

Roth Bros., Inc.                         Centerior Energy Services, Inc.            HVAC services

Roth Bros., Inc.                         FirstEnergy Generation Corp.               HVAC services

Roth Bros., Inc.                         FirstEnergy Nuclear Operating Company      HVAC services

Roth Bros., Inc.                         FirstEnergy Solutions Corp.                HVAC services

Roth Bros., Inc.                         Ohio Edison Company                        HVAC services

Sautter Crane Rental, Inc.               FirstEnergy Solutions Corp.                Crane rental

Sautter Crane Rental, Inc.               Jersey Central Power & Light Company       Crane rental


                                                                   6





                                                    ITEM 3 - ASSOCIATE TRANSACTIONS


Part I - Transactions Performed by Reporting Companies on Behalf of Associate Companies (continued)


                                                                                                                         Total
                                                                                                                         Amount
Reporting Company Rendering Services      Associate Company Receiving Services       Types of Services Rendered          Billed
------------------------------------      ------------------------------------       --------------------------          ------

                                                                               
Sautter Crane Rental, Inc.                Metropolitan Edison Company                Crane rental

Warrenton River Terminal, Ltd.            FirstEnergy Generation Corp.               Loading, unloading and storage
                                                                                     of coal and petcoke


Note:  The information provided in Item 3 presents the activities of the reporting period only. The amounts required under
----   the caption "Total Amount Billed" are being filed pursuant to request for confidential treatment.


                                                            7







                                              ITEM 3 - ASSOCIATE TRANSACTIONS (Continued)


Part II - Transactions Performed by Associate Companies on Behalf of Reporting Companies


                                                                                                                         Total
                                                                                                                         Amount
Associate Company Rendering Services       Reporting Company Receiving Services      Types of Services Rendered          Billed
------------------------------------       ------------------------------------      --------------------------          ------

                                                                               
FirstEnergy Service Company                GPU Diversified Holdings LLC              Legal and certain general
                                                                                     and administrative
                                                                                     services

FirstEnergy Generation Corp.               Bay Shore Power Company                   Sale of fuel oil

FirstEnergy Generation Corp.               Bay Shore Power Company                   Plant operation & maintenance
                                                                                     services

FirstEnergy Service Company                FirstEnergy Solutions Corp.               General and administrative
                                                                                     services


Note: The  information  provided in Item 3 presents the  activities of the reporting  period only.  The amounts  required
----  under the caption "Total Amount Billed" are being filed pursuant to request for confidential treatment.


                                                            8







                                        ITEM 4 - SUMMARY OF AGGREGATE INVESTMENT



Investments in energy-related companies:
                                                                                                                 
   Total average consolidated capitalization as of  December 31, 2003*                    $21,193,345                     Line 1
                                                   ------------------
       Total capitalization multiplied by 15% (line 1 multiplied by 0.15)                   3,179,002                     Line 2
       Greater of $50 million or line 2                                                                    $3,179,002     Line 3

       Total current aggregate investment:
       (categorized by major line of energy-related business)
           Development and commercialization of photovoltaics (Category II)                     4,524
           Production, conversion, sale and distribution of thermal energy
             products (Category VI)                                                            29,063
           Sale of technical, operational, management, and other services
             related to HVAC, refrigeration systems (Category VII)                              4,295
           Fuel transportation, handling and storage facilities (Category IX)                      50
                                                                                           ----------

                Total current aggregate investment                                                             37,932     Line 4
                                                                                                            ---------

       Difference between the greater of $50 million or 15% of capitalization
           and the total aggregate investment of the registered holding company
            system (line 3 less line 4)                                                                    $3,141,070     Line 5
                                                                                                            =========


Note: The caption "Total average consolidated  capitalization"  includes total common equity, preferred equity (including
----  amounts due within one year), long-term debt (including amounts due within one year) and short-term debt.

      The caption  "Total  current  aggregate  investment"  includes all amounts  invested or committed to be invested in
      energy-related  companies on or after the date of effectiveness  of Rule 58 (March 24, 1997), or after  FirstEnergy
      Corp.  registered as a holding company (November 7, 2001) for which there is recourse,  directly or indirectly,  to
      FirstEnergy Corp. or any subsidiary company thereof. The amounts do not include purchase accounting adjustments.

*     Total  capitalization  amounts  for  December  2002 and March 2003 have been  revised to  reflect  restatements  in
      FirstEnergy's Amendment No. 2 of 2002 Form 10-K/A and Amendment No. 1 of March 2003 Form 10-Q.

                                                            9






                                               ITEM 5 - OTHER INVESTMENTS


                                                                                    Change in
                                                    Aggregate Investment as   Investments During           Reason for Change
Major Line of Energy-Related Business                of September 30, 2003     Reporting Period              in Investments
-------------------------------------               -----------------------   ------------------   --------------------------------

                                                                                           
Energy management services (Category I)                  $ 1,766 (1)                 -              No change.

Development and commercialization of                      55,623 (2)              $1,384            In the fourth quarter of 2003,
electrotechnologies (Category II)                                                                   FirstEnergy through its direct
                                                                                                    subsidiary, GPU Diversified
                                                                                                    Holdings, LLC made $400 thousand
                                                                                                    investment to EnerTech Capital
                                                                                                    Partners II, LP. FirstEnergy
                                                                                                    also made $984 thousand capital
                                                                                                    contribution to PowerSpan Corp.

Energy services and retail energy sales
(Category V)                                              18,158 (3)                 -               No change.

Production, conversion, sale and distribution of          70,913 (4)                 -               No change.
thermal energy products (Category VI)

Sale of technical, operational, management, and          198,279 (5)             $(7,164)            FirstEnergy sold Ancoma, Inc.
other services related to HVAC, refrigeration                                                        on December 29, 2003.
systems (Category VII)

Fuel transportation, handling and storage                  4,959 (6)                 -               No change.
facilities (Category IX)

Development and commercialization of technologies             46 (7)                 -               No change.
that utilize coal waste by-products (Category X)


(1)  Includes $1,766 that was invested in energy-related  companies,  prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(2)  Includes $52,483 that was invested in energy-related companies,  prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(3)  Includes $18,158 that was invested in energy-related companies,  prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(4)  Includes $41,850 that was invested in energy-related companies,  prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(5)  Includes $193,984 that was invested in energy-related companies, prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(6)  Includes $4,909 that was invested in energy-related  companies,  prior to FirstEnergy Corp. registered as a holding
     company (November 7, 2001).
(7)  Includes $46 that was invested in  energy-related  companies,  prior to FirstEnergy  Corp.  registered as a holding
     company (November 7, 2001).

                                                           10






                   ITEM 6 - FINANCIAL STATEMENTS AND EXHIBITS


A.  Financial Statements

A-1  Financial statements of FirstEnergy  Solutions Corp. - not required for the
     last quarterly period of the registered holding company's fiscal year.

A-2  Financial statements of GPU Diversified Holdings LLC - not required for the
     last quarterly period of the registered holding company's fiscal year.

A-3  Financial statements of Bay Shore Power Company - not required for the last
     quarterly period of the registered holding company's fiscal year.

A-4  Financial  statements of Centerior Energy Services,  Inc - not required for
     the last quarterly period of the registered holding company's fiscal year.

A-5  Financial  statements of Warrenton River Terminal,  Ltd. - not required for
     the last quarterly period of the registered holding company's fiscal year.

A-6  Financial statements of Dunbar Mechanical, Inc. - not required for the last
     quarterly period of the registered holding company's fiscal year.

A-7  Financial  statements  of  Edwards  Electrical  &  Mechanical,  Inc.  - not
     required for the last quarterly period of the registered  holding company's
     fiscal year.

A-8  Financial  statements  of  Elliot-Lewis  Corporation - not required for the
     last quarterly period of the registered holding company's fiscal year.

A-9  Financial statements of L.H. Cranston and Sons, Inc. - not required for the
     last quarterly period of the registered holding company's fiscal year.

A-10 Financial  statements  of Roth  Bros.,  Inc.  - not  required  for the last
     quarterly period of the registered holding company's fiscal year.

A-11 Financial  statements of The Hattenbach Company - not required for the last
     quarterly period of the registered holding company's fiscal year.

A-12 Financial statements of R.P.C. Mechanical, Inc. - not required for the last
     quarterly period of the registered holding company's fiscal year.

                                       11





ITEM 6 - FINANCIAL STATEMENTS AND EXHIBITS (Continued)


A. Financial Statements (Continued)


A-13 Financial statements of Spectrum Controls Systems,  Inc. - not required for
     the last quarterly period of the registered holding company's fiscal year.


A-14 Financial  statements  of GPU  Solar,  Inc.  - not  required  for the  last
     quarterly period of the registered holding company's fiscal year.

                                       12





             ITEM 6 - FINANCIAL STATEMENTS AND EXHIBITS (Continued)


B.  Exhibits
    --------

    Contracts Required by Item 3
    ----------------------------

       B-1    Stockholders Agreement made and entered into as of January 7, 1998
              by and among GPU  International,  Inc.,  AstroPower,  Inc. and GPU
              Solar,  Inc. (in  connection  with the sale of GPU  International,
              Inc. on December 22, 2000, the Stockholders  Agreement was amended
              such that GPU International,  Inc. transferred its interest in GPU
              Solar,  Inc.  and  its  rights  and  responsibilities   under  the
              Stockholders   Agreement  to  GPU  Diversified   Holdings  LLC)  -
              incorporated  by  reference  to  Exhibit  B-12 to GPU's  Quarterly
              Report on Form U-9C-3 for the period ended December 31, 2000.

       B-2    Amendment No. 1 to Stockholders Agreement made and entered into as
              of  December  1,  2000  by  and  among  GPU  International,  Inc.,
              AstroPower, Inc., GPU Diversified Holdings LLC and GPU Solar, Inc.
              (this amendment essentially transferred GPU International,  Inc.'s
              interest in GPU Solar,  Inc.  and its rights and  responsibilities
              under the Stockholders  Agreement to GPU Diversified Holdings LLC)
              -  incorporated  by reference  to Exhibit B-13 to GPU's  Quarterly
              Report on Form U-9C-3 for the period ended December 31, 2000.

       B-3    Contract between  FirstEnergy  Service Company and GPU Diversified
              Holdings   LLC  to  provide   legal  and   certain   general   and
              administrative services - incorporated by reference to Exhibit B-3
              to  FirstEnergy's  Quarterly  Report on Form U-9C-3 for the period
              ended September 30, 2003.

       B-4    Contract  between  FirstEnergy  Service  Company  and  FirstEnergy
              Solutions   Corp.  to  provide  legal  and  certain   general  and
              administrative services - incorporated by reference to Exhibit B-4
              to  FirstEnergy's  Quarterly  Report on Form U-9C-3 for the period
              ended September 30, 2003.


       Note:  Services rendered by Dunbar Mechanical,  Inc. and Roth Bros., Inc.
              to their  associate  companies  are provided  pursuant to purchase
              order contracts.


C.  Certificate of FirstEnergy Corp.
    -------------------------------

                                       13




                                    SIGNATURE


     The undersigned  registered  holding company has duly caused this quarterly
report to be signed on its  behalf by the  undersigned  officer  thereunto  duly
authorized  pursuant to the  requirements  of the Public Utility Holding Company
Act of 1935.



                                               FIRSTENERGY CORP.



March 23, 2004
                                By:          /s/ Harvey L. Wagner
                                      -------------------------------------
                                                 Harvey L. Wagner
                                           Vice President, Controller
                                          and Chief Accounting Officer
                                          (Principal Accounting Officer)


                                       14