Exhibit 10.1
                                                                EXECUTION COPY
                                  AMENDMENT

      This AMENDMENT, dated as of December 5, 2002 (this "Amendment"),  is made
to that certain Credit  Agreement,  dated as of October 11, 2002,  (the "Credit
Agreement"),  among Alliant Energy  Corporation (the  "Borrower"),  the lenders
party thereto (the "Lenders") and Bank One, NA, as agent (the "Agent").

                             PRELIMINARY STATEMENT:

      The  Borrower,  the Lenders  and the Agent  previously  entered  into the
Credit  Agreement.  The Borrower has  requested  that the Lenders  agree to the
amendment  to the  Credit  Agreement  as set  forth  herein,  and the  Majority
Lenders have agreed to such  request,  subject to the terms and  conditions  of
this Amendment.  Therefore,  for good and valuable  consideration,  the receipt
and adequacy of which are hereby acknowledged, the parties agree as follows:

      SECTION 1.  Definitions.  Capitalized  terms  used but not defined herein
have the meanings assigned to such terms in the Credit Agreement.

      SECTION 2. Amendment.  Section 5.02(a) of the Credit Agreement is amended
by (i)  deleting  the  word  "and"  from  clause  (x)  of  such  Section,  (ii)
replacing  the heading  "(xi)" in clause (xi) of such  Section with the heading
"(xii)" and (iii) inserting the following new clause (xi) immediately following
clause (x) of such Section:

      (xi) Liens  on the  capital  stock  and  assets  of  Whiting  Petroleum
Corporation ("Whiting")  to secure not more than $230 million  aggregate
principal  amount of Debt of Whiting under a loan agreement to be entered into
by Whiting on or before December 31, 2002; and

      SECTION  3.  Conditions  of  Effectiveness.  Section 2 of this  Amendment
shall  become  effective  as of the date first set forth above when each of the
following conditions shall have been fulfilled:

      (i)    the Majority Lenders and the Borrower shall have  executed  and
delivered to the Agent a counterpart of this Amendment;

      (ii)   the  Borrower shall have paid (A) to the Agent, for the account of
each Lender that shall have  executed and  delivered to the Agent a counterpart
of this  Amendment  on or before 12:00 noon (New York City time) on December 5,
2002,  an upfront fee of 0.10% of the  aggregate  amount of the  Commitment  of
such  Lender,  and (B) all fees payable  hereunder  or payable  pursuant to the
Fee Letter, dated the date hereof, between the Borrower and the Agent; and

<PAGE>

      (iii)  the representations and warranties  set forth in Section 4 hereof
shall be true and correct on and as of the date of  effectiveness  of this
Amendment as though made on and as of such date.

      SECTION 4.  Representations  and Warranties.  The Borrower represents and
warrants that (a) the  representations  and warranties  contained in Article IV
of the Credit  Agreement,  as amended  hereby (with each  reference  therein to
(i) "this  Agreement",  "hereunder"  and words of like import  referring to the
Credit  Agreement  being  deemed to be a reference  to this  Amendment  and the
Credit Agreement,  as amended hereby,  and (ii) "Loan Documents",  "thereunder"
and  words of like  import  being  deemed to  include  this  Amendment  and the
Credit  Agreement,  as amended  hereby)  are true and  correct on and as of the
date  hereof  as  though  made on and as of such  date,  and (b ) no event  has
occurred and is  continuing,  or would result from the  execution  and delivery
of this  Amendment,  that  constitutes  an  Unmatured  Default  or an  Event of
Default.

      SECTION  5.  Effect  on the  Credit  Agreement.  Except  as  specifically
provided  above,  the Credit  Agreement  shall continue to be in full force and
effect and is hereby in all respects  ratified and  confirmed.  The  execution,
delivery and  effectiveness  of this Amendment  shall not,  except as expressly
provided  herein,  operate  as a waiver  of any  right,  power or remedy of the
Lenders under the Credit  Agreement,  nor  constitute a waiver of any provision
of the Credit Agreement.

      SECTION 6. Costs and Expenses.  The Borrower  agrees to pay on demand all
costs and expenses of the Agent in connection with the  preparation,  execution
and delivery of this Amendment,  including,  without limitation, the reasonable
fees  and  out-of-pocket  expenses  of  counsel  for  the  Agent  with  respect
thereto,  and all costs and expenses  (including,  without limitation,  counsel
fees  and  expenses),  if any,  in  connection  with the  enforcement  (whether
through negotiations, legal proceedings or otherwise) of this Amendment.

      SECTION 7. Execution in  Counterparts.  This Amendment may be executed in
any  number  of  counterparts  and by  different  parties  hereto  in  separate
counterparts,  each of which when so executed and delivered  shall be deemed to
be an original and all of which taken  together  shall  constitute  but one and
the same instrument.

      SECTION 8.  Governing  Law.  This  Amendment  shall be  governed  by, and
construed in accordance with, the internal laws of the State of the New York.

<PAGE>

     IN WITNESS  WHEREOF,  the parties  hereto have caused this Agreement to be
executed by their  respective  officers  thereunto duly  authorized,  as of the
date first above written.



                                         ALLIANT ENERGY CORPORATION

                                         By:  /s/ Enrique Bacalao
                                              ------------------------
                                         Name: Enrique Bacalao
                                         Title:   Assistant Treasurer





                                         BANK ONE, NA,
                                         as Agent, LC Issuing Bank and as Lender

                                         By:   /s/ Madeleine N. Pember
                                               -----------------------------
                                         Name:  Madeleine N. Pember
                                         Title:   Director








                       SIGNATURE PAGE TO AMENDMENT