FIRSTENERGY CORP.

                                       TO

                              THE BANK OF NEW YORK,
       (successor by merger to United States Trust Company of New York)

                     Trustee under the GPU, Inc. Indenture,
                          dated as of December 1, 2000

                     --------------------------------------

                             Supplemental Indenture

                       Providing for Succession By Merger

                     --------------------------------------

                          Dated as of November 7, 2001


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                             SUPPLEMENTAL INDENTURE
                             ----------------------


      SUPPLEMENTAL INDENTURE,  dated as of November 7, 2001, between FIRSTENERGY
CORP.,  a  corporation  of the State of Ohio,  whose  address  is 76 South  Main
Street, Akron, Ohio 44308,  (hereinafter sometimes called the Successor Company)
and THE BANK OF NEW YORK (successor to United States Trust Company of New York),
a corporation of the State of New York, whose address is 5 Penn Plaza, New York,
New York 10001  (hereinafter  sometimes  called the Trustee),  Trustee under the
Indenture, dated as of December 1, 2000 (hereinafter called the Indenture), from
GPU, INC., a corporation of the Commonwealth of  Pennsylvania,  whose address is
300 Madison Avenue,  Morristown,  New Jersey 07962 (hereinafter sometimes called
the  Predecessor  Company),  to United  States Trust  Company of New York,  this
Supplemental  Indenture  (hereinafter  called the Supplemental  Indenture) being
supplemental thereto.

      WHEREAS,  Effective  June 26, 2001,  The Bank of New York  acquired all or
substantially all of the corporate trust business of United States Trust Company
of New York,  and by virtue of the  provisions of Section 912 of the  Indenture,
The Bank of New York became the successor  Trustee under the Indenture,  without
the  execution  or  filing of any  paper or any  further  act on the part of any
parties to the Indenture; and

      WHEREAS, the Predecessor Company has heretofore issued and the Trustee has
heretofore authenticated and delivered, in accordance with the provisions of the
Indenture, $300,000,000 principal amount of 7.70% Debentures, Series A due 2005;
and

      WHEREAS,  Article Eleven of the Indenture  provides upon any merger of the
Predecessor  Company into any other entity (herein  sometimes  called a Merger),
for the execution and delivery to the Trustee by the successor  corporation of a
supplemental  indenture whereby the successor corporation shall expressly assume
the due and  punctual  payment of the  principal  of and  premium,  if any,  and
interest,  if any, on all Outstanding  Securities issued under the Indenture and
the  performance  and  observance  of every  covenant and  obligation  under the
Indenture on the part of the Company to be performed or observed; and

      WHEREAS,  Article  Eleven of the Indenture  provides that upon the Merger,
the successor  corporation,  into which the Predecessor Company is merged, shall
succeed to, and be substituted for, the Predecessor Company and may exercise any
right and power of the  Predecessor  Company under the  Indenture  with the same
effect as if such successor  corporation had been named the Predecessor  Company
therein,  and  thereafter,  the  Predecessor  Company  shall be  relieved of all
obligations  and covenants  under the Indenture and the  Outstanding  Securities
thereunder; and

      WHEREAS,  on November 7, 2001 (Effective  Time),  the Predecessor  Company
will merge into the  Successor  Company  upon such terms as to fully comply with
the provisions of Article Eleven of the Indenture; and


<PAGE>


      WHEREAS, the Successor Company, pursuant to appropriate resolutions of its
Board of Directors,  has authorized the execution of this Supplemental Indenture
to provide,  among other  things,  for the  assumption  of the  Indenture by the
Successor  Company in  compliance  with Article  Eleven and as  hereinafter  set
forth; and

      WHEREAS,  pursuant  to  Section  1201 of the  Indenture,  the  Trustee  is
authorized  to enter into one or more  supplemental  indentures  to evidence the
succession of another  entity to the  Predecessor  Company and the assumption by
any such successor of the covenants of the Predecessor  Company contained in the
Indenture  and  the  Securities,  all  as  provided  in  Article  Eleven  of the
Indenture.

                                   ARTICLE I.

            PROVISIONS RELATING TO ARTICLE ELEVEN OF THE INDENTURE


      SECTION 1.1 The  Successor  Company does as of the  Effective  Time hereby
expressly  assume  (i) the due and  punctual  payment  of the  principal  of and
premium,  if any, and interest on all  Outstanding  Securities  issued under the
Indenture according to their tenor and (ii) the due and punctual performance and
observance of every covenant and  obligation  under the Indenture on the part of
the Predecessor Company to be performed and observed.

      SECTION 1.2 It is hereby  declared that, in accordance with the provisions
of Section  1102 of the  Indenture,  the  Successor  Company,  having  expressly
assumed (i) the due and punctual payment of the principal  premium,  if any, and
interest on all Outstanding  Securities issued under the Indenture  according to
their tenor and (ii) the due and punctual  performance  and  observance  of each
covenant  and  obligation  under the  Indenture  on the part of the  Predecessor
Company to be performed or observed,  shall succeed to, and be substituted  for,
and may  exercise  every right and power of the  Predecessor  Company  under the
Indenture  as of the  Effective  Time with the same  effect as if the  Successor
Company had been named as the Predecessor  Company therein,  and the Predecessor
Company shall be relieved of all  obligations  and covenants under the Indenture
and the Securities Outstanding thereunder.


                                  ARTICLE II.

                            MISCELLANEOUS PROVISIONS

SECTION  2.1  Subject  to  the  amendments  provided  for in  this  Supplemental
Indenture, the terms defined in the Indenture, as heretofore supplemented, shall
for all purposes of this Supplemental  Indenture have the meanings  specified in
the Indenture, as heretofore supplemented.

SECTION 2.2 The Trustee  hereby  accepts the trusts herein  declared,  provided,
created  or  supplemented  and  agrees  to  perform  the same upon the terms and
conditions herein and in the Indenture,  as heretofore  supplemented,  set forth
and upon the following terms and conditions:


<PAGE>


      The Trustee shall not be  responsible  in any manner  whatsoever for or in
respect of the validity or sufficiency of this Supplemental  Indenture or for or
in respect of the recitals  contained herein,  all of which recitals are made by
the Successor Company.  In general,  each and every term and condition contained
in  Article  Nine  of the  Indenture  shall  apply  to and  form  part  of  this
Supplemental Indenture with the same force and effect as if the same were herein
set forth in full with such omissions, variations and insertions, if any, as may
be appropriate  to make the same conform to the provisions of this  Supplemental
Indenture.

SECTION  2.3  Whenever  in this  Supplemental  Indenture  any one of the parties
hereto is named or  referred  to,  this  shall,  subject  to the  provisions  of
Articles Nine and Eleven of the  Indenture,  be deemed to include the successors
and  assigns  of such  party,  and  all the  covenants  and  agreements  in this
Supplemental  Indenture contained,  by or on behalf of the Successor Company, or
by or on behalf of the Trustee,  shall, subject as aforesaid,  bind and inure to
the  respective  benefits  of the  respective  successors  and  assigns  of such
parties, whether so expressed or not.

SECTION 2.4 Nothing in this  Supplemental  Indenture  expressed  or implied,  is
intended,  or shall be construed to confer upon, or to give to, any person, firm
or corporation,  other than the parties hereto and the holders of the Securities
Outstanding under the Indenture,  any right,  remedy or claim under or by reason
of this Supplemental Indenture or any covenant, condition,  stipulation, promise
or agreement hereof, and all the covenants, conditions,  stipulations,  promises
and agreements in this Supplemental Indenture contained,  by or on behalf of the
Successor  Company,  shall be for the sole and exclusive  benefit of the parties
hereto, and of the holders of the Securities Outstanding under the Indenture.

SECTION  2.5  This   Supplemental   Indenture   shall  be  executed  in  several
counterparts,  each  of  which  shall  be an  original  and all of  which  shall
constitute but one and the same instrument.

SECTION 2.6 This  Supplemental  Indenture  shall be governed by and construed in
accordance with the laws of the State of New York.


<PAGE>


      IN WITNESS  WHEREOF,  the parties  hereto  have  caused this  Supplemental
Indenture to be duly executed, as of the day and year first above written.



                                    FIRSTENERGY CORP.


                                    By
                                      ----------------------------




                                    THE BANK OF NEW YORK,
                                    Trustee


                                    By
                                      ----------------------------
                                             Louis P. Young
                                             Vice President