Execution Copy
                                                                 --------------


EXHIBIT 4.16a



                         FOURTH SUPPLEMENTAL INDENTURE


                         DATED AS OF DECEMBER 26, 2002





                        ALLIANT ENERGY RESOURCES, INC.,
                                   Company,


                          ALLIANT ENERGY CORPORATION,
                                 As Guarantor,

                                      and

                        U.S. BANK NATIONAL ASSOCIATION,
                                  as Trustee





                     Fourth Supplemental Indenture to the
                                   Indenture
                         dated as of November 4, 1999

<PAGE>

           FOURTH SUPPLEMENTAL INDENTURE, dated as of December 26, 2002 (the
"Fourth Supplemental Indenture"), among ALLIANT ENERGY RESOURCES, INC., a
Wisconsin corporation (the "Company"), ALLIANT ENERGY CORPORATION, a
Wisconsin corporation, as guarantor (the "Guarantor"), and U.S. BANK NATIONAL
ASSOCIATION, as successor to FIRSTAR BANK, N.A., as Trustee (the "Trustee").

                   RECITALS OF THE COMPANY AND THE GUARANTOR

           The Company and the Guarantor have heretofore executed and
delivered to the Trustee an Indenture, dated as of November 4, 1999 (as
supplemented by the First Supplemental Indenture dated as of November 4,
1999, the Second Supplemental Indenture dated as of February 1, 2000 and the
Third Supplemental Indenture dated as of November 15, 2001, and as may be
further supplemented and amended from time to time, the "Indenture"),
providing for the issuance from time to time of the Company's unsecured
unsubordinated debentures, notes or other evidences of indebtedness (the
"Securities"), to be issued in one or more series as provided in the Indenture.

           It is provided in Section 2.02 of the Indenture that the Company,
the Guarantor and the Trustee may enter into indentures supplemental thereto
to establish the form or terms of Securities of any series.

           The Company and the Guarantor desire to supplement and amend the
Indenture to allow for the issuance of Securities to be initially sold within
the United States to U.S. Persons that are Qualified Institutional Buyers and
issued in the form of one or more Restricted Global Securities deposited with
the Trustee, as custodian for the Depositary, and registered in the name of a
nominee of the Depositary.

           The Company and the Guarantor desire to set forth the terms and
form of a new series of Restricted Securities to be known as the Company's
9.75% Senior Notes, in an aggregate principal amount of THREE HUNDRED MILLION
DOLLARS ($300,000,000) (the "9.75% Senior Notes") and guaranteed by the
Guarantor.

           The 9.75% Senior Notes and the certificate of authentication to be
borne by the 9.75% Senior Notes are to be substantially in the form set forth
in Exhibit A hereto.

        NOW, THEREFORE, THIS FOURTH SUPPLEMENTAL INDENTURE WITNESSETH:

           For and in consideration of the premises and the purchase of the
9.75% Senior Notes by the Holders (as defined herein) thereof, it is mutually
covenanted and agreed as follows for the equal and ratable benefit of the
Holders of the 9.75% Senior Notes:

                                  ARTICLE 1.

                                  AMENDMENTS

           Section 1.01.  Article 1 of the Indenture shall be amended by
inserting in Section 1.01 the following new terms with the following
definitions in the appropriate alphabetic positions:

                "Additional Interest" with respect to the 9.75% Senior Notes
      has the meaning set forth in Section 2.06 of the Fourth Supplemental
      Indenture.

                "Adjustment Date" means any date on which the interest rate on
      the 9.75% Senior Notes is increased or decreased in accordance with the
      terms of the 9.75% Senior Notes upon a ratings change by Moody's
      Investors Services, Inc. or Standard & Poor's Rating Service.

                "Capitalized Lease Obligations" means obligations to pay rent
      or other amounts under any lease of (or other arrangement conveying the
      right to use) real and/or personal property which obligation is required
      to be classified and accounted for as a capital lease on a balance sheet

<PAGE>

      prepared in accordance with GAAP, and for purposes hereof the amount of
      such obligations shall be the capitalized amount determined in
      accordance with such principles.

                "Closing Time" means, with respect to the 9.75% Senior Notes,
      December 26, 2002, the date of initial issuance of the Securities issued
      hereunder.

                "Consolidated Indebtedness" means, at any date of
      determination, the aggregate Indebtedness of the Guarantor and its
      Consolidated Subsidiaries determined on a consolidated basis in
      accordance with GAAP, but shall not include Nonrecourse Indebtedness of
      any Consolidated Subsidiary of the Guarantor.

                "Consolidated Net Worth" means, at any time of  determination,
      the net worth of such the Guarantor and its Consolidated Subsidiaries as
      determined in accordance with GAAP.

                "Consolidated Subsidiary" means any Subsidiary of the
      Guarantor whose accounts are or are required to be consolidated with the
      accounts of the Guarantor in accordance with GAAP.

                "Consolidated Total Capitalization" means, at any date of
      determination, the sum of (i) Consolidated Indebtedness;
      (ii) consolidated equity of the common shareowners of the Guarantor and
      its Consolidated Subsidiaries; (iii) consolidated equity of the
      preference shareowners of the Guarantor and its Consolidated
      Subsidiaries; and (iv) consolidated equity of the preferred shareowners
      of the Guarantor and its Consolidated Subsidiaries, in each case
      determined at such date in accordance with GAAP, excluding, however,
      from such calculation, amounts identified as "Accumulated Other
      Comprehensive Income (Loss)" in the financial statements of the
      Guarantor set forth in the Guarantor's report on Form 10-K or 10-Q, as
      the case may be, filed most recently with the SEC prior to the date of
      such determination.

                "EBITDA" means, with respect to any period, the sum of
      operating income of the Guarantor and its Consolidated Subsidiaries for
      such period, as determined on a consolidated basis in accordance with
      GAAP, plus all amounts deducted in the computation thereof on account of
      depreciation and amortization.

                "ERISA" means the Employee Retirement  Income Security Act of
      1974, as amended from time to time, and the regulations promulgated and
      rulings issued thereunder.

                "ERISA Affiliate" means,  with respect to any Person,  any
      trade or business (whether or not incorporated) which is a member of a
      group of which such Person is a member and which is under common control
      within the meaning of the regulations under Section 414(b) or (c) of the
      Internal Revenue Code of 1986, as amended from time to time.

                "Fourth Supplemental Indenture" means the Fourth Supplemental
      Indenture dated as of December 26, 2002, among the Company, the
      Guarantor and the Trustee.

                "GAAP" means, with respect to the 9.75% Senior Notes,
      generally accepted accounting principles in the United States on the
      date of the Fourth Supplemental Indenture.

                "Indebtedness" means, for any person, any and all
      indebtedness, liabilities and other monetary obligations of such person
      (i) for borrowed money or evidenced by bonds, debentures, notes or other
      similar instruments, (ii) to pay the deferred purchase price of property
      or services (except trade accounts payable arising and repaid in the
      ordinary course of business), (iii) Capitalized Lease Obligations,
      (iv) under reimbursement or similar agreements with respect to letters
      of credit (other than trade letters of credit) issued to support
      indebtedness or obligations of such person or of others of the kinds
      referred to in clauses (i) through (iii) above and clause (v) below,
      (v) reasonably quantifiable obligations under direct guaranties or
      indemnities, or under support agreements, in respect of, and reasonably
      quantifiable obligations (contingent or otherwise) to purchase or
      otherwise acquire, or otherwise to assure a creditor against loss in
      respect of, or to assure an obligee against failure to make payment in

<PAGE>

      respect of, indebtedness or obligations of others of the kinds referred
      to in clauses (i) through (iv) above, and (vi) in respect of unfunded
      vested benefits under Plans.  In determining Indebtedness for any
      person, there shall be included accrued interest on the principal amount
      thereof to the extent such interest has accrued for more than six months.

                "Interest Coverage Ratio" means, as of any date, the ratio of
      (i) EBITDA of the Guarantor and its Consolidated Subsidiaries for the
      most recently ended four fiscal quarters for which internal financial
      statements are available ending on or prior to such date, as determined
      on a consolidated basis in accordance with GAAP to (ii) the Interest
      Expense payable by the Guarantor and its Consolidated Subsidiaries
      during such four-quarter period, determined in the case of clauses (i)
      and (ii) on a pro forma basis as if the additional indebtedness had been
      incurred and proceeds of the additional indebtedness applied at the
      beginning of such four-quarter period.

                "Interest Expense" means, with respect to any period, interest
      expense of the Guarantor and its Consolidated Subsidiaries for such
      period, including both capitalized and noncapitalized interest and the
      interest component of capital lease obligations and all debt discount
      and expense amortized during such period, as determined on a
      consolidated basis in accordance with GAAP.

                "Multiple Employer Plan" means a single employer plan, as
      defined in Section 4001(a)(15) of ERISA, which is subject to Title IV of
      ERISA and which (i) is maintained for employees of the Guarantor or an
      ERISA Affiliate of the Guarantor and at least one Person other than the
      Guarantor and its ERISA Affiliates or (ii) was so maintained and in
      respect of which the Guarantor or an ERISA Affiliate of the Guarantor
      could have liability under Section 4064 or 4069 of ERISA in the event
      such plan has been or were to be terminated.

                "Nonrecourse Indebtedness" means Indebtedness of any person
      that finances the acquisition, development, ownership or operation of an
      asset in respect of which the obligee of such Indebtedness has no
      recourse whatsoever to such person or any of its Affiliates other than:
      (i) recourse to the named obligor with respect to such Indebtedness (the
      "Debtor") for amounts limited to the cash flow or net cash flow (other
      than historic cash flow or historic net cash flow) from the asset; and
      (ii) recourse to the Debtor for the purposes only of enabling amounts to
      be claimed in respect of such Indebtedness in an enforcement of any
      security interest or lien given by the Debtor over the asset or the
      income, cash flow or other proceeds deriving from the asset (or given by
      any shareholder or the like in the Debtor over its shares or like
      interest in the capital of the Debtor) to secure the Indebtedness, but
      only if the extent of the recourse to the Debtor is limited solely to
      the amount of any recoveries made on any such enforcement; and
      (iii) recourse to the Debtor generally or indirectly to any Affiliate of
      the Debtor, under any form of assurance, undertaking or support, which
      recourse is limited to a claim for damages (other than liquidated
      damages and damages required to be calculated in a specified way) for a
      breach of an obligation (other than a payment obligation or an
      obligation to comply or to procure compliance by another with any
      financial ratios or other tests of financial condition) by the Person
      against which such recourse is available.

                "Permitted Indebtedness" means:

                (i) Indebtedness of Alliant Energy Corporate Services, Inc.,
      so long as it is a mutual service company that provides services to
      utility and non-utility Subsidiaries of the Guarantor pursuant to the
      Public Utility Holding Company Act of 1935, as amended.

                (ii) intercompany Indebtedness owed to the Company, to the
      Guarantor or to any Consolidated Subsidiary;

                (iii) Indebtedness to the cash management programs established
      by the Guarantor pursuant to the SEC's approval under the Public Utility
      Holding Company Act of 1935, as amended, for (A) the Guarantor's
      domestic public utility Subsidiaries and Alliant Energy Corporate
      Services, Inc., known as the "utility money pool" and (B) the
      Guarantor's non-utility Subsidiaries, known as the "non-utility money
      pool";

<PAGE>

                (iv) Nonrecourse Indebtedness;

                (v) Indebtedness incurred to fund Alliant Energy Corporate
      Services, Inc. or the cash management program of the Guarantor's
      domestic public utility Subsidiaries, known as the "utility money pool";

                (vi) Permitted Refinancing Indebtedness;

                (vii) Indebtedness arising from the deposit and collection of
      checks and similar items in the ordinary course of business;

                (viii) Indebtedness arising from the guarantee of other
      Indebtedness permitted by this Indenture;

                (ix) Indebtedness represented by letters of credit issued in
      order to provide security for workers' compensation claims, payment
      obligations in connection with self-insurance or similar requirements in
      the ordinary course of business;

                (x) Indebtedness in respect of bid, payment and performance
      bonds, bankers' acceptances, workers' compensation claims, surety or
      appeal bonds, payment obligations in connection with self-insurance or
      similar obligations, and bank overdrafts (and letters of credit in
      respect thereof) in the ordinary course of business;

                (xi) Indebtedness consisting of guarantees, indemnities or
      obligations in respect of purchase price adjustments in connection with
      the acquisition or disposition of assets;

                (xii) Indebtedness of the Guarantor and its Consolidated
      Subsidiaries in existence on the date of original issuance of the 9.75%
      Senior Notes, until such amounts are repaid;

                (xiii) Indebtedness represented by the 9.75% Senior Notes and
      the guarantee of the Guarantor related thereto; and

                (xiv) additional Indebtedness in an aggregate principal amount
      not to exceed $100 million at any one time outstanding.

                "Permitted Refinancing Indebtedness" means any Indebtedness of
      the Guarantor or any of its Consolidated Subsidiaries issued in exchange
      for, or the net proceeds of which are used to extend, refinance, renew,
      replace, defease or refund other Indebtedness of the Guarantor or any of
      its Subsidiaries permitted to be incurred by this Indenture; provided
      that:

                (i)  the principal amount (or accreted value, if applicable)
      of such Permitted Refinancing Indebtedness does not exceed the principal
      amount of (or accreted value, if applicable), plus accrued interest on,
      the Indebtedness so extended, refinanced, renewed, replaced, defeased or
      refunded (plus the amount of reasonable expenses incurred in connection
      therewith);

                (ii) such Permitted Refinancing Indebtedness has a final
      maturity date later than the final maturity date of, and has a Weighted
      Average Life to Maturity equal to or greater than the Weighted Average
      Life to Maturity of, the Indebtedness being extended, refinanced,
      renewed, replaced, defeased or refunded;

                (iii)if the Indebtedness being extended, refinanced, renewed,
      replaced, defeased or refunded is Indebtedness that is subordinate or
      junior in right of payment to the 9.75% Senior Notes or the Guarantee
      pursuant to written agreement, such Permitted Refinancing Indebtedness
      is subordinated in right of payment to the 9.75% Senior Notes and the
      Guarantee on terms at least as favorable to the holders of the 9.75%

<PAGE>

      Senior Notes as those contained in the documentation governing such
      subordinated debt being extended, refinanced, renewed, replaced,
      defeased or refunded; and

                (iv) such Indebtedness is incurred by the Person who is the
      obligor on the Indebtedness being extended, refinanced, renewed,
      replaced, defeased or refunded.

                "Person" means an individual, partnership, corporation
      (including a business trust), limited liability company,  joint stock
      company,  trust, unincorporated association, joint venture or other
      entity, or a government or any political subdivision or agency thereof.

                "Plan" means a Single Employer Plan or a Multiple Employer
      Plan.

                "Registration Default" with respect to the 9.75% Senior Notes
      has the meaning set forth in Section 2.06 of the Fourth Supplemental
      Indenture.

                "Registration Rights Agreement" means, with respect to the
      9.75% Senior Notes, the Registration Rights Agreement to be executed
      among the Company, the Guarantor and Merrill Lynch, Pierce, Fenner &
      Smith Incorporated, Utendahl Capital Partners, L.P., and The Williams
      Capital Group, L.P., as initial purchasers, in connection with the
      offering of the 9.75% Senior Notes.

                "9.75% Senior Notes" has the meaning set forth in Section 2.01
      of the Fourth Supplemental Indenture.

                "Single Employer Plan" means a single employer plan, as
      defined in Section 4001(a)(15) of ERISA, which is subject to Title IV of
      ERISA and which (i) is maintained for employees of the Guarantor or an
      ERISA Affiliate of the Guarantor and no Person other than the Guarantor
      and its ERISA Affiliates, or (ii) was so maintained and in respect of
      which the Guarantor or an ERISA Affiliate of the Guarantor could have
      liability under Section 4069 of ERISA in the event  such plan has been
      or were to be terminated.

                "Subsidiary" with respect to the 9.75% Senior Notes means,
      with respect to any Person, any corporation or unincorporated entity of
      which more than 50% of the outstanding capital stock (or comparable
      interest) having ordinary voting power (irrespective of whether at the
      time capital stock (or comparable interest) of any other class or
      classes of such corporation or entity shall or might have voting power
      upon the occurrence of any contingency) is at the time directly or
      indirectly owned by said Person (whether directly or through one or more
      other Subsidiaries).  In the case of an unincorporated entity, a Person
      shall be deemed to have more than 50% of the interest having ordinary
      voting power only if such Person's vote in respect of such interests
      comprises more than 50% of the total voting power of all such interests
      in the unincorporated entity.

                "Weighted Average Life to Maturity" means, when applied to any
      Indebtedness at any date, the number of years obtained by dividing:

                (i)  the sum of the products obtained by multiplying (a) the
      amount of each then remaining installment, sinking fund, serial maturity
      or other required payments of principal, including payment at final
      maturity, in respect thereof, by (b) the number of years (calculated to
      the nearest one-twelfth) that will elapse between such date and the
      making of such payment, by

                (ii) the then outstanding principal amount of such
      Indebtedness.

           Section 1.02.  Article 1 of the Indenture shall be amended by
amending and restating in their entirety the following definitions in Section
1.01:

                "Exchange Offer" shall mean the exchange offer by the Company
      and the Guarantor of Exchange Securities for Registrable Securities, as
      provided for in a related registration rights agreement.

<PAGE>

                "Exchange Offer Registration Statement" shall mean an exchange
      offer registration statement on Form S-4 (or, if applicable, on another
      appropriate form), and all amendments and supplements to such
      registration statement, including the Prospectus contained therein, all
      exhibits thereto and all documents incorporated by reference therein.

                "Supplemental Indenture" means the First Supplemental
      Indenture, the Second Supplemental Indenture, the Third Supplemental
      Indenture, the Fourth Supplemental Indenture and any further
      supplemental indentures that the Company, the Guarantor and the Trustee
      may execute from time to time.

           Section 1.03.  The Indenture shall be amended by adding exhibits
titled "Exhibit G" and "Exhibit H," respectively, immediately following
Exhibit F of the Indenture.  Exhibit G to the Indenture shall be the form of
the 9.75% Senior Note and the related guarantee attached as Exhibit A to this
Fourth Supplemental Indenture and Exhibit H to the Indenture shall be the
form of Incurrence Certificate attached as Exhibit B to this Fourth
Supplemental Indenture.

           Section 1.04.  To the extent necessary, the forms of Transfer
Certificate and Exchange Certificate, each as attached to the Indenture as
Exhibits B and C, respectively, shall be amended to refer to the appropriate
Securities and the appropriate dates.

                                  ARTICLE 2.

                     PROVISIONS FOR THE 9.75% SENIOR NOTES

           Section 2.01.  There shall be a series of Securities entitled
"9.75% Senior Notes" (herein designated the "9.75% Senior Notes").  The form
of the 9.75% Senior Notes, the Guarantees issued by the Guarantor and the
Trustee's certificate of authentication to be borne thereby shall be
substantially in the forms set forth in Exhibit A hereto and shall be
executed, authenticated and delivered in accordance with the provisions of,
and shall in all respects be subject to, all of the terms, conditions and
covenants of the Indenture and this Fourth Supplemental Indenture, including,
but not limited to, the provisions of the Indenture with respect to the
transfer, exchange and replacement thereof. The aggregate principal amount of
the 9.75% Senior Notes that may be executed by the Company and authenticated
by the Trustee hereunder shall be limited to THREE HUNDRED MILLION DOLLARS
($300,000,000); provided, however, any exchanges or replacements of the 9.75%
Senior Notes made pursuant to the Indenture and the Fourth Supplemental
Indenture following the original issuance thereof, shall not be counted
against this limit.

           Section 2.02.  In accordance with the terms and conditions of the
Indenture, the Company may issue and sell the 9.75% Senior Notes inside the
United States without registration under the Securities Act in reliance on
Rule 144A thereunder.

           Section 2.03.  Except as provided below, the 9.75% Senior Notes
shall be represented initially in the form of a Restricted Global Security.
Each Restricted Global Security shall be registered in the name of a nominee
of the Depositary and deposited on behalf of the purchasers of the 9.75%
Senior Notes represented thereby with a custodian for the Depositary for
credit to the respective accounts of the purchasers (or to such other
accounts as they may direct).  Except as set forth below, each Restricted
Global Security shall be in the form of the 9.75% Senior Notes attached
hereto as Exhibit A and may be transferred, in whole and not in part, only to
another nominee of the Depositary or to a successor of the Depositary or its
nominee.

           Section 2.04.  (a)  Each Restricted Global Security, or any 9.75%
Senior Notes that may be issued in exchange for an interest in a Restricted
Global Security, shall be dated as provided in Section 2.03 of the Indenture,
shall mature on January 15, 2013 and shall bear interest at the initial rate
of 9.75% per annum (subject to increase pursuant to Section 2.06 hereof and
the terms of the 9.75% Senior Notes) from December 26, 2002, payable
semiannually on January 15 and July 15 in each year, commencing with July 15,
2003, until payment of the principal amount shall have been made or duly
provided for.  The record dates with respect to the interest payment dates
for the 9.75% Senior Notes shall be January 1 and July 1 (whether or not a
business day), respectively. The holder of record of 9.75% Senior Notes on

<PAGE>

any record date for the payment of interest shall be entitled to receive the
interest payable on such interest payment date.

           (b)  Both principal of and interest on the 9.75% Senior Notes shall
be payable at the office of the Paying Agent in St. Paul, Minnesota and the
Borough of Manhattan, The City of New York, New York or at any other office
maintained by the Company or the Guarantor, as the case may be, for such
purpose; provided that interest may be payable, at the option of the Company
or the Guarantor, as the case may be, by check mailed to the registered
address of the person entitled thereto as such address shall appear on the
registry books of the Company. On each interest payment date the Trustee
shall pay to the registered holder interest accrued in respect of such 9.75%
Senior Notes.  Payment of principal on 9.75% Senior Notes shall be paid to
the registered holder or upon his order only upon presentation and surrender
for payment of such 9.75% Senior Notes on or after the payment date at the
offices of the Company or the Guarantor, as the case may be, in St. Paul,
Minnesota and the Borough of Manhattan, The City of New York, New York or at
any other office of the Company or the Guarantor, as the case may be,
maintained for such purpose.

           (c)  The 9.75% Senior Notes shall not be convertible into or
exchangeable for equity securities of the Company or the Guarantor.

           (d)  The 9.75% Senior Notes shall not be subject to any sinking
fund.

           (e)  The 9.75% Senior Notes shall not be included for listing on
any national securities exchange.

           (f)  The Trustee, at its Corporate Trust Office located at 180 East
Fifth Street, St. Paul, Minnesota 55101, shall initially act as Paying Agent
for the 9.75% Senior Notes.

           Section 2.05.  (a)  So long as a nominee of the Depositary is the
registered owner of any Restricted Global Security, such nominee shall be
considered the sole owner and holder of the 9.75% Senior Notes represented by
such Restricted Global Security under the Indenture, as supplemented and
amended hereby. Except as herein provided, owners of beneficial interests in
any Restricted Global Security shall not be entitled to have 9.75% Senior
Notes represented by the such Restricted Global Security registered in their
names, shall not receive or be entitled to receive physical delivery of 9.75%
Senior Notes in certificated form and shall not be considered the owners or
holders thereof under the Indenture.

           (b)  None of the Company, the Guarantor or the Trustee shall have
any responsibility or liability for any aspect of the records relating to or
payments made on account of beneficial ownership interests in any Restricted
Global Security, or for maintaining, supervising or reviewing any records
relating to such beneficial interests.

           Section 2.06.  In the event that (a) the Exchange Offer
Registration Statement is not filed with the SEC on or prior to the 120th
calendar day following the Closing Time, (b) the Exchange Offer Registration
Statement has not been declared effective on or prior to the 210th calendar
day following the Closing Time, (c) the Exchange Offer is not consummated, on
or prior to the 45th calendar day following the effective date of the
Exchange Offer Registration Statement or (d) if required, the Shelf
Registration Statement is not declared effective on or prior to the 210th
calendar day following the Closing Time (each such event referred to in
clauses (a) through (d) above, a "Registration Default"), the interest rate
borne by the 9.75% Senior Notes shall be increased ("Additional Interest"),
in the amount of one-half of one percent (0.50%) per annum, which rate will
increase by one-quarter of one percent (0.25%) at the beginning of each
subsequent 90-day period during which a Registration Default is continuing,
provided that the maximum aggregate increase in the interest rate pursuant to
this Section 2.06 will in no event exceed two percent (2.0%) per annum.
Following the cure of all Registration Defaults with respect to the 9.75%
Senior Notes the accrual of Additional Interest will cease and the interest
rate will revert to the rate that otherwise would be in effect had such
Registration Default not occurred.

           If the Shelf Registration Statement with respect to the 9.75%
Senior Notes is unusable by the Holders for any reason after the Shelf
Registration Statement has been declared effective by the SEC, and the
aggregate number of days in any consecutive twelve-month period for which the
Shelf Registration Statement shall not be usable exceeds 30 days in the

<PAGE>

aggregate, then the interest rate borne by the 9.75% Senior Notes, so long as
any such notes are required to be registered under the Registration Rights
Agreement, will be increased by one-half of one percent (0.50%) per annum of
the principal amount of the 9.75% Senior Notes for the first 90-day period
(or portion thereof) beginning on the 31st day following the date that such
Shelf Registration Statement ceases to be usable, which rate shall be
increased by an additional one-quarter of one percent (0.25%) per annum of
the principal amount of the 9.75% Senior Notes at the beginning of each
subsequent 90-day period, provided that the maximum aggregate increase in the
interest rate pursuant to this Section 2.06 will in no event exceed two
percent (2.00%) per annum.  Any amounts payable under this Section 2.06 shall
also be deemed "Additional Interest" for purposes of the Indenture and the
Registration Rights Agreement.  Upon the Shelf Registration Statement once
again becoming usable, the interest rate borne by the 9.75% Senior Notes will
be reduced to the interest rate that otherwise would be in effect had the
Shelf Registration Statement not become unusable, provided the Company and
the Guarantor are otherwise in compliance with this the Indenture and the
Registration Rights Agreement at such time.  Additional Interest shall be
computed based on the actual number of days elapsed in each 90-day period in
which the Shelf Registration Statement is unusable.

           The Company and the Guarantor shall notify the Trustee within three
business days after each and every Event Date with respect to the 9.75%
Senior Notes.  Additional Interest with respect to the 9.75% Senior Notes
shall be paid by depositing with the Trustee, in trust, for the benefit of
the Holders of the 9.75% Senior Notes, on or before the applicable semiannual
interest payment date, immediately available funds in sums sufficient to pay
the Additional Interest then due.  The Additional Interest due shall be
payable on each interest payment date to the record Holder of the 9.75%
Senior Notes entitled to receive the interest payment to be paid on such date
as set forth in the Indenture.  Each obligation to pay Additional Interest
shall be deemed to accrue from and including the day following the applicable
Event Date.

           Section 2.07.  The 9.75% Senior Notes will be redeemable at the
Company's option in whole or in part at any time, on at least 30 days' but
not more than 60 days' prior written notice mailed to the registered holders
of the 9.75% Senior Notes, at a price equal to the greater of (i) 100% of the
principal amount of the 9.75% Senior Notes being redeemed and (ii) the sum of
the present values of the principal amount of the 9.75% Senior Notes to be
redeemed and the remaining scheduled payments of interest on the 9.75% Senior
Notes from the redemption date to January 15, 2013, discounted  from their
respective scheduled payment dates to the redemption date semi-annually
(assuming a 360-day year consisting of twelve 30-day months) at a discount
rate equal to the Treasury Yield plus 50 basis points, plus accrued interest
on the 9.75% Senior Notes to the redemption date.

           Section 2.08.  Neither the Company nor the Guarantor shall, and
each shall not permit any Consolidated Subsidiary other than, in the case of
the Guarantor, the Guarantor's domestic public utility Subsidiaries, to,
directly or indirectly, create, incur, issue, assume, Guarantee or otherwise
become directly or indirectly liable, contingently or otherwise, with respect
to (collectively, "incur") any Indebtedness (other than Permitted
Indebtedness) if, after giving pro forma effect to the incurrence of such
Indebtedness, any of the following is true:

           (a)  Consolidated Net Worth would be less than $1.2 billion;

           (b)  the ratio of Consolidated Indebtedness to Consolidated Total
Capitalization would exceed 0.70 to 1.00; or

           (c)  the Interest Coverage Ratio would be less than 2.0 to 1.0.

Upon the incurrence of any Indebtedness (other than Permitted Indebtedness)
by the Company, the Guarantor or any Consolidated Subsidiary other than, in
the case of the Guarantor, the Guarantor's domestic public utility
Subsidiaries, the Guarantor shall deliver to the Trustee a certificate
substantially in the form set forth in Exhibit C hereto (the "Certificate of
Incurrence") signed by one or more officers of the Guarantor holding at least
two of the following three titles:  Chief Financial Officer, Treasurer and
Chief Accounting Officer of the Guarantor.

           Section 2.09.  The Guarantor shall not, and shall not permit any
Subsidiary, other than the Guarantor's domestic public utility Subsidiaries,
to issue, assume or guarantee any Debt if the Debt is secured by any Lien
upon any of its property or assets (other than cash), without effectively
securing the outstanding 9.75% Senior Notes (together with any other

<PAGE>

indebtedness or obligation then existing or thereafter created ranking
equally with such 9.75% Senior Notes) equally and ratably with the Debt.
This limitation does not apply to:

           (a)  Liens in existence on the date of original issuance of the
      9.75% Senior Notes;

           (b)  (i) any Lien created or arising over any property or assets
      which the Guarantor or a Subsidiary acquires, constructs or creates, but
      only if (A) such Lien secures only principal amounts (not exceeding the
      cost of the acquisition, construction or creation) of Debt incurred for
      the purposes of the acquisition, construction or creation, together with
      any costs, expenses, interest and fees incurred in connection with the
      acquisition, construction or creation or a guarantee given in connection
      with the acquisition, construction or creation, (B) the Lien is created
      or arises on or before 90 days after the completion of the acquisition,
      construction or creation and (C) the Lien is confined solely to the
      property or assets so acquired, constructed or created; or (ii) any Lien
      to secure the Debt incurred by the Guarantor or a Subsidiary in
      connection with a specifically identifiable project where the Lien
      relates and is confined to a property or properties (including, without
      limitation, shares or other rights of ownership in the entities which
      own such property or project) involved in such project and acquired by
      the Guarantor or a Subsidiary after the date of original issuance of the
      9.75% Senior Notes and the recourse of the creditors in respect of the
      Debt is limited to any or all of such project and property (including as
      aforesaid);

           (c)  any Lien securing amounts not more than 90 days overdue or
      otherwise being contested in good faith;

           (d)  (i)  rights of financial institutions to offset credit
      balances in connection with the operation of cash management programs
      established for the Guarantor's or any Subsidiary's benefit or in
      connection with the issuance of letters of credit for the Guarantor's or
      any Subsidiary's benefit;

                (ii)  any Lien securing Debt incurred by the Guarantor or any
      Subsidiary in connection with the financing of accounts receivable;

                (iii)  any Lien incurred or deposits made in the ordinary
      course of business, including, but not limited to, (A) any mechanics',
      materialmen's, carriers', workmen's, vendors' or other like Liens and
      (B) any Liens securing amounts in connection with workers' compensation,
      unemployment insurance and other types of social security;

                (iv)  any Lien upon specific items of the Guarantor's or any
      Subsidiary's inventory or other goods and proceeds securing the
      Guarantor's or any Subsidiary's obligations in respect of bankers'
      acceptances issued or created to facilitate the purchase, shipment or
      storage of such inventory or other goods;

                (v)  any Lien incurred or deposits made securing the
      performance of tenders, bids, leases, trade contracts (other than for
      borrowed money), statutory obligations, surety bonds, appeal bonds,
      government contracts, performance bonds, return-of-money bonds and other
      obligations of like nature incurred by the Guarantor or any Subsidiary
      in the ordinary course of business;

                (vi)  any Lien constituted by a right of set off or right over
      a margin call account or any form of cash or cash collateral or any
      similar arrangement for obligations incurred by the Guarantor or any
      Subsidiary in respect of the hedging or management of risks under
      transactions involving any currency or interest rate swap, cap or collar
      arrangements, forward exchange transaction, option, warrant, forward
      rate agreement, futures contract or other derivative instrument of any
      kind;

                (vii)  any Lien arising out of title retention or like
      provisions in connection with the purchase of goods and equipment by the
      Guarantor or any Subsidiary in the ordinary course of business; and

<PAGE>

                (viii)  any Lien securing reimbursement obligations under
      letters of credit, guarantees and other forms of credit enhancement
      given in connection with the purchase of goods and equipment by the
      Guarantor or any Subsidiary in the ordinary course of business;

           (e)  (i)  Liens on any property or assets acquired from an entity
      which is merged with or into the Guarantor or any Subsidiary and is not
      created in anticipation of any such transaction (unless the Lien was
      created to secure or provide for the payment of any part of the purchase
      price of the entity to be acquired) and (ii) any Lien on any property or
      assets existing at the time of acquisition by the Guarantor or any
      Subsidiary and which is not created in anticipation of the acquisition
      (unless the Lien was created to secure or provide for the payment of any
      part of the purchase price of the property or assets so acquired);

           (f)  (i)  Liens required by any contract or statute in order to
      permit the Guarantor or any Subsidiary to perform any contract or
      subcontract made by it with or at the request of a governmental entity
      or any department, agency or instrumentality of a governmental entity,
      or to secure partial, progress, advance or any other payments by the
      Guarantor or any Subsidiary to a governmental unit under the provisions
      of any contract or statute; (ii) any Lien securing industrial revenue,
      development or similar bonds issued by the Guarantor or any Subsidiary
      or for its respective benefit, provided that the industrial revenue,
      development or similar bonds are nonrecourse to the Guarantor and/or the
      applicable Subsidiary; and (iii) any Lien securing taxes or assessments
      or other applicable governmental charges or levies;

           (g)  (i)  any Lien which arises under any order of attachment,
      distraint or similar legal process arising in connection with court
      proceedings and any Lien which secures the reimbursement obligation for
      any bond obtained in connection with an appeal taken in any court
      proceeding, so long as the execution or other enforcement of the Lien
      arising in connection with such legal process is effectively stayed and
      the claims secured by the Lien are being contested in good faith and, if
      appropriate, by appropriate legal proceedings, or any Lien in favor of a
      plaintiff or defendant in any action before a court or tribunal as
      security for costs or expenses; or (ii) any Lien arising by operation of
      law or by order of a court or tribunal or any Lien arising by an
      agreement of similar effect, including, without limitation, judgment
      liens; or

           (h)  any extension, renewal or replacement (or successive
      extensions, renewals or replacements), as a whole or in part, of any
      Liens referred to in clauses (a) through (g) above, for amounts not
      exceeding the principal amount of the Debt secured by the Lien so
      extended, renewed or replaced, so long as the extension, renewal or
      replacement Lien is limited to all or a part of the same property or
      assets that were covered by the Lien that was extended, renewed or
      replaced (plus improvements on such property or assets);

provided, however, the Guarantor or any such Subsidiary may create or permit
--------  -------
to subsist Liens over any of the Guarantor's or Subsidiary's property or
assets so long as the aggregate amount of Debt secured by all Liens that the
Guarantor or any such Subsidiary incurs (excluding the amount of Debt secured
by Liens set forth in clauses (a) through (h) above) does not exceed 10% of
the Guarantor's Consolidated Net Tangible Assets.

           Section 2.10.  The Company and the Guarantor shall notify the
Trustee within three business days after each and every Adjustment Date.

                                  ARTICLE 3.

                                 MISCELLANEOUS

           Section 3.01.  Capitalized terms used but not defined herein shall
have the respective meanings set forth in the Indenture, as may be amended
and supplemented from time to time in accordance therein.

           Section 3.02.  Except as supplemented and amended hereby, the
Indenture is in all respects ratified and confirmed, and all of the terms,
provisions and conditions thereof shall be and remain in full force and
effect, and this Fourth Supplemental Indenture and all its provisions shall
be deemed a part thereof.

<PAGE>

           Section 3.03.  In case any provision in this Fourth Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality
and enforceability of the remaining provisions shall not in any way be
affected or impaired thereby.

           Section 3.04.  If any provision of this Fourth Supplemental
Indenture limits, qualifies or conflicts with any other provision hereof or
of the Indenture which provision is required to be included in the Indenture
by any of the provisions of the Trust Indenture Act, such required provision
shall control.

           Section 3.05.  THIS FOURTH SUPPLEMENTAL INDENTURE AND ALL DISPUTES,
CONTROVERSIES OR CLAIMS ARISING OUT OF OR RELATING TO THIS FOURTH
SUPPLEMENTAL INDENTURE OR A BREACH HEREOF SHALL BE GOVERNED BY AND CONSTRUED
IN ACCORDANCE WITH THE LAWS OF THE STATE OF WISCONSIN WITHOUT REGARD TO THE
CONFLICTS OF LAWS AND RULES OF SAID STATE.

           Section 3.06.  This Fourth Supplemental Indenture has been
simultaneously executed in several counterparts, each of which shall be
deemed to be an original, and all such counterparts shall together constitute
but one and the same instrument.  Delivery by telecopier of an executed
signature page hereto shall be effective as delivery of a manually executed
counterpart hereof.

           Section 3.07.  This Fourth Supplemental Indenture shall be deemed
to have been executed on the date of the acknowledgment thereof by the
officer of the Trustee who signed it on behalf of the Trustee.



          [THE REST OF THIS PAGE HAS INTENTIONALLY BEEN LEFT BLANK.]


<PAGE>


           IN WITNESS WHEREOF, the Company, the Guarantor and the Trustee have
caused their names to be signed hereto by their respective officers thereunto
duly authorized and their respective corporate seals, duly attested, to be
hereunto affixed, all as of the day and year first above written.


                                    ALLIANT ENERGY RESOURCES, INC.
ATTEST:




By:_/s/ Enrique Bacalao                 By:_/s/ Thomas L. Hanson
    --------------------------              ------------------------------------
    Name:  Enrique Bacalao                  Name:  Thomas L. Hanson
    Title:  Assistant Treasurer             Title:  Vice President and Treasurer


                                            ALLIANT ENERGY CORPORATION,
ATTEST:                                     as Guarantor




By:_/s/ Enrique Bacalao                 By:_/s/ Thomas L. Hanson
    ---------------------------             ------------------------------------
    Name:  Enrique Bacalao                  Name:  Thomas L. Hanson
    Title:  Assistant Treasurer             Title:  Vice President and Treasurer


                                            U.S. BANK NATIONAL ASSOCIATION,
                                            as Trustee




                                        By:_/s/ Steven J. Peterson
                                            ------------------------------------
                                            Name:  Steven J. Peterson
                                            Title:  Trust Officer


<PAGE>

                                                                      EXHIBIT A


                          EXHIBIT G TO THE INDENTURE

                         [Form of 9.75% Senior Notes]


           Unless this certificate is presented by an authorized
representative of The Depository Trust Company, a New York corporation
("DTC"), to Alliant Energy Resources, Inc., or its agent for registration of
transfer, exchange or payment, and any certificate issued is registered in
the name of Cede & Co. or to such other entity or in such other name as is
requested by an authorized representative of DTC (and any payment hereon is
made to Cede & Co. or to such other entity as is requested by an authorized
representative of DTC), ANY TRANSFER, PLEDGE OR OTHER USE HEREOF FOR VALUE OR
OTHERWISE BY OR TO ANY PERSON IS WRONGFUL since the registered owner hereof,
Cede & Co., has an interest herein.

           Transfers of this Global Security shall be limited to transfers in
whole, but not in part, to nominees of Cede & Co. or to a successor thereof
or such successor's nominee [and transfers of portions of this Global
Security shall be limited to transfers made in accordance with the
restrictions set forth in Section 2.20 of the Indenture referred to in this
Global Security].

           [THE NOTES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF
1933, AS AMENDED (THE "SECURITIES ACT"), OR ANY STATE OR OTHER SECURITIES
LAWS. NEITHER THIS NOTE NOR ANY INTEREST OR PARTICIPATION HEREIN MAY BE
REOFFERED, SOLD, ASSIGNED, TRANSFERRED, PLEDGED, ENCUMBERED OR OTHERWISE
DISPOSED OF IN THE ABSENCE OF SUCH REGISTRATION OR UNLESS THE TRANSACTION IS
EXEMPT FROM, OR NOT SUBJECT TO, THE REGISTRATION REQUIREMENTS OF THE
SECURITIES ACT. BY ITS ACQUISITION HEREOF, THE HOLDER (1) REPRESENTS THAT IT
IS A "QUALIFIED INSTITUTIONAL BUYER" ("QIB") (AS DEFINED IN RULE 144A ("RULE
144A") UNDER THE SECURITIES ACT), (2) AGREES NOT TO OFFER, SELL OR OTHERWISE
TRANSFER THIS NOTE PRIOR TO (X) THE DATE WHICH IS TWO YEARS (OR SUCH SHORTER
PERIOD OF TIME AS PERMITTED BY RULE 144(K) UNDER THE SECURITIES ACT) AFTER
THE LATER OF THE ORIGINAL ISSUE DATE OF THE NOTES AND THE LAST DATE ON WHICH
ALLIANT ENERGY RESOURCES, INC. OR ANY "AFFILIATE" (AS DEFINED IN RULE 144
UNDER THE SECURITIES ACT) OF ALLIANT ENERGY RESOURCES, INC. WAS THE OWNER OF
THIS NOTE (OR ANY PREDECESSOR OF THIS NOTE) OR (Y) SUCH LATER DATE, IF ANY,
AS MAY BE REQUIRED BY APPLICABLE LAW (THE "RESALE RESTRICTION TERMINATION
DATE") EXCEPT (A) TO ALLIANT ENERGY RESOURCES, INC., (B) PURSUANT TO A
REGISTRATION STATEMENT THAT HAS BEEN DECLARED EFFECTIVE UNDER THE SECURITIES
ACT, (C) FOR SO LONG AS THE SECURITIES ARE ELIGIBLE FOR RESALE PURSUANT TO
RULE 144A, TO A PERSON IT REASONABLY BELIEVES IS A "QUALIFIED INSTITUTIONAL
BUYER" AS DEFINED IN RULE 144A THAT PURCHASES FOR ITS OWN ACCOUNT OR FOR THE
ACCOUNT OF A QUALIFIED INSTITUTIONAL BUYER, IN EACH CASE TO WHOM NOTICE IS
GIVEN THAT THE TRANSFER IS BEING MADE IN RELIANCE ON RULE 144A OR (D)
PURSUANT TO ANOTHER AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF
THE SECURITIES ACT SUBJECT IN EACH OF THE FOREGOING CASES OF ANY REQUIREMENT
OF LAW THAT THE DISPOSITION OF ITS PROPERTY OR THE PROPERTY OF SUCH INVESTOR
ACCOUNT OR ACCOUNTS BE AT ALL TIMES WITHIN ITS OR THEIR CONTROL, AND (3)
AGREES THAT IT WILL GIVE TO EACH PERSON TO WHOM THIS NOTE IS TRANSFERRED A
NOTICE SUBSTANTIALLY TO THE EFFECT OF THIS LEGEND; PROVIDED THAT ALLIANT
ENERGY RESOURCES, INC. AND THE TRUSTEE SHALL HAVE THE RIGHT PRIOR TO ANY SUCH
OFFER, SALE OR TRANSFER (I) PURSUANT TO CLAUSE (D) TO REQUIRE THE DELIVERY OF
AN OPINION OF COUNSEL, CERTIFICATION AND/OR OTHER INFORMATION SATISFACTORY TO
EACH OF THEM, AND (II) IN EACH OF THE FOREGOING CASES, BUT ONLY IF THIS NOTE
IS NOT A GLOBAL SECURITY (AS DEFINED IN THE INDENTURE REFERRED TO HEREIN), TO
REQUIRE THAT A CERTIFICATION OF TRANSFER IN THE FORM APPEARING ON THE OTHER
SIDE OF THIS NOTE IS COMPLETED AND DELIVERED BY THE TRANSFEROR TO ALLIANT
ENERGY RESOURCES, INC. AND THE TRUSTEE.  THIS LEGEND WILL BE REMOVED UPON THE
REQUEST OF THE HOLDER AFTER THE RESALE RESTRICTION TERMINATION DATE.]

<PAGE>

                        ALLIANT ENERGY RESOURCES, INC.
                          9.75% SENIOR NOTES DUE 2013

CUSIP No. 018803 ____ __
$300,000,000


Global Note


           Alliant Energy Resources, Inc., a corporation duly organized and
existing under the laws of the State of Wisconsin (the "Company," which term
includes any successor person under the Indenture hereinafter referred to),
for value received, hereby promises to pay to Cede & Co. or registered
assigns, the principal sum of THREE HUNDRED MILLION DOLLARS ($300,000,000) on
January 15, 2013, at the office or agency of the Company referred to below,
in such coin or currency of the United States of America as at the time of
payment is legal tender for the payment of public and private debts, and to
pay interest thereon in like coin or currency from December 26, 2002, or from
the most recent interest payment date on which interest has been paid or duly
provided for, semi-annually in arrears on January 15 and July 15 in each
year, commencing July 15, 2003, at the initial rate of 9.75% per annum, until
the principal hereof is paid or made available for payment, and (to the
extent lawful) to pay interest at the same rate per annum on any overdue
principal and premium and on any overdue installment of interest until paid.

           The interest rate borne by this Senior Note will be increased at
any time to and including January 1, 2004 upon a rating change by Moody's
Investors Services, Inc. ("Moody's") or Standard & Poor's Rating Service
("Standard & Poor's") on or prior to such date that causes the rating of this
Senior Note by either agency to be below Baa3 in the case of Moody's and BBB-
in the case of Standard & Poor's (or equivalent rating by such agency if such
rating reference is no longer in effect) (a "Rating Downgrade").  Beginning
with and including the date on which a Rating Downgrade is assigned (the
"Step-Up Date"), the interest rate borne by this Senior Note will be the rate
otherwise applicable plus one percent (1.00%) per annum.  If on any date
through January 1, 2004 (the "Step-Down Date"), subsequent to a Step-Up Date,
a new rating change by Moody's or Standard & Poor's causes the ratings of
this Senior Note to be above Ba1 in the case of Moody's and BB+ in the case
of Standard & Poor's, the interest rate borne by this Senior Note will be the
rate otherwise applicable less one percent (1.00%) per annum.  Such decrease
will be effective from and including the Step-Down Date.  There is no limit
on the number of times through January 1, 2004 that the interest rate borne
by this Senior Note can be adjusted up or down based on a rating change by
Moody's and Standard & Poor's during this period, provided, however, that the
interest rate shall never increase more than one percent (1.00%) due to
ratings downgrades, and following January 1, 2004, the interest rate borne on
this Senior Note will no longer be subject to increase or decrease and such
interest rate, as in effect on January 1, 2004, will remain in effect during
the remaining life of this Senior Note.

           Interest so payable, and punctually paid or duly provided for, on
any interest payment date, as provided in the Indenture, shall be paid to the
person in whose name this Senior Note (or one or more predecessor Senior
Notes) is registered at the close of business on the record date for such
interest, which shall be January 1 or July 1 (whether or not a business day),
as the case may be, next preceding such interest payment date.  Any such
interest not so punctually paid or duly provided for will forthwith cease to
be payable to the person in whose name this Senior Note is registered on such
record date and may either be paid to the person in whose name this Senior
Note is registered at the close of business on a record date for the payment
of such defaulted interest to be fixed by the Trustee, notice whereof shall
be given to the person in whose name this Senior Note is registered not less
than ten days prior to such record date, or be paid at any time in any other
lawful manner, all as more fully provided in the Indenture.

           This Senior Note is a "book-entry" security and is being registered
in the name of Cede & Co. as nominee of The Depository Trust Company ("DTC"),
a clearing agency.  Subject to the terms of the Indenture, dated as of
November 4, 1999 (as supplemented by the First Supplemental Indenture dated
as of November 4, 1999, the Second Supplemental Indenture dated as of
February 1, 2000, the Third Supplemental Indenture dated as of November 15,
2001, the Fourth Supplemental Indenture dated as of December 26, 2002 and as
supplemented and amended from time to time, the "Indenture"), among the
Company, Alliant Energy Corporation (the "Guarantor"), and U.S. Bank National

<PAGE>

Association, as successor to Firstar Bank, N.A., as trustee (the "Trustee"),
and except as provided therein, this Senior Note will be held by a clearing
agency or its nominee, and beneficial interests will be held by beneficial
owners through the book-entry facilities of such clearing agency or its
nominee in integrals of $1,000 in excess thereof.

           The statements set forth in the restrictive legend above are an
integral part of the terms of this Senior Note and by acceptance hereof each
holder of this Senior Note agrees to be subject to and bound by the terms and
provisions set forth in such legend.

           The Trustee will make payments of principal of and interest on
(except as otherwise provided below) this Senior Note by wire transfer of
immediately available funds. Notwithstanding the above, the final payment on
this Senior Note will be made after due notice by the Trustee of the pendency
of such payment and only upon presentation and surrender of this Senior Note
at its principal corporate trust office or such other offices or agencies
appointed by the Trustee for that purpose and such other locations provided
in the Indenture.

           Payments of principal of (and premium, if any) and interest on this
Senior Note will be made at the offices or agency of the Company or the
Guarantor, as the case may be, maintained for that purpose in St. Paul,
Minnesota and the Borough of Manhattan, The City of New York, New York in
such coin or currency of the United States of America as at the time of
payment is legal tender for payments of public and private debts; provided,
however, that at the option of the Company or the Guarantor, as the case may
be, payment of interest may be made by check mailed to the address of the
person entitled thereto as such address shall appear in the register of the
Company.

           This Senior Note is one of a duly authorized issue of Securities of
the Company, designated 9.75% Senior Notes (the "9.75% Senior Notes"),
limited in aggregate principal amount at any time outstanding to THREE
HUNDRED MILLION DOLLARS ($300,000,000) which may be issued under the Fourth
Supplemental Indenture.  Reference is hereby made to the Indenture, the
Fourth Supplemental Indenture and all other indentures supplemental thereto
for a statement of the respective rights, limitations of rights, duties,
obligations and immunities thereunder of the Company, the Guarantor, the
Trustee and the Holders of the 9.75% Senior Notes, and the terms upon which
the 9.75% Senior Notes are, and are to be, authenticated and delivered.  All
terms used in this Senior Note that are defined in the Indenture shall have
the meanings assigned to them in the Indenture.

           The Holder of this Senior Note is entitled to the benefits of the
Registration Rights Agreement, dated as of December 26, 2002 (the
"Registration Rights Agreement"), among the Company, the Guarantor and the
initial purchasers named therein (the "Initial Purchasers").  In the event
that (i) the Company and the Guarantor fail to file an Exchange Offer
Registration Statement with respect to the 9.75% Senior Notes with the
Securities and Exchange Commission (the "Commission") on or prior to the
120th calendar day following the Closing Time, (ii) the Commission does not
declare such Exchange Offer Registration Statement effective on or prior to
the 210th calendar day following the Closing Time, (iii) the Exchange Offer
is not consummated on or prior to the 45th calendar day following the
effective date of the Exchange Offer Registration Statement or (iv) if
required, a Shelf Registration Statement with respect to the 9.75% Senior
Notes is not declared effective by the Commission on or prior to the 210th
calendar day following the Closing Time (each, a "Registration Default"), the
per annum interest rate borne by the 9.75% Senior Notes shall be increased by
one-half of one percent (0.50%) per annum for the first 90-day period
following the Registration Default.  The interest rate borne by the 9.75%
Senior Notes will be increased by an additional one-quarter of one percent
(0.25%) per annum for the subsequent 90-day period (or portion thereof)
during which any such Registration Default continues up to a maximum
aggregate increase in the annual interest rate pursuant to this paragraph of
two percent (2.0%) per annum.  Following the cure of all Registration
Defaults, the interest rate borne by the 9.75% Senior Notes shall be reduced
to the interest rate borne by the 9.75% Senior Notes that otherwise would be
in effect had such Registration Default not occurred.  If the Shelf
Registration Statement is unusable by the Holders for any reason after the
Shelf Registration Statement has been declared effective by the Commission,
and the aggregate number of days in any consecutive twelve-month period for
which the Shelf Registration is unusable exceeds 30 days in the aggregate,
then the interest rate borne by the 9.75% Senior Notes will be increased by
one-half of one percent (0.50%) per annum of the principal amount of the
9.75% Senior Notes for the first 90-day period (or a portion thereof)
beginning the 31st day following the date that such Shelf Registration
Statement ceases to be usable, which rate shall be increased by an additional
one-quarter of one percent (0.25%) per annum of the principal amount of 9.75%

<PAGE>

Senior Notes at the beginning of each subsequent 90-day period, provided that
the maximum aggregate increase in the interest rate pursuant to this
paragraph will in no event exceed two percent (2.0%) per annum.  Upon the
Shelf Registration Statement once again becoming usable, the interest rate
borne by the 9.75% Senior Notes will be reduced to the interest rate that
otherwise would be in effect had the Shelf Registration Statement not become
unusable.  All accrued additional interest shall be paid to Holders by the
Company in the same manner and at the same time as interest is paid pursuant
to the Indenture.  All terms used in this Senior Note that are defined in the
Registration Rights Agreement shall have the meanings assigned to them in the
Registration Rights Agreement.

           Each purchaser of 9.75% Senior Notes, by its acquisition thereof,
will be deemed to have acknowledged, represented to and agreed with the
Initial Purchasers, the Company and the Guarantor as follows:

                (1)  Such purchaser understands and acknowledges that the
      9.75% Senior Notes have not been registered under the Securities Act or
      any other applicable securities laws, are being offered for resale in
      transactions not requiring registration under the Securities Act or any
      other securities laws including sales pursuant to Rule 144A under the
      Securities Act, and may not be offered, sold or otherwise transferred
      except in compliance with the registration requirements of the
      Securities Act or any other applicable securities law, or pursuant to an
      exemption therefrom or in a transaction not subject thereto, and in each
      case in compliance with the conditions for transfer set forth in
      paragraph (4) below.

                (2)  Such purchaser is not an "affiliate" (as defined in Rule
      144 under the Securities Act) of the Company and it is a QIB and is
      aware that any sale of 9.75% Senior Notes to it will be made in reliance
      on Rule 144A and such acquisition will be for its own account or for the
      account of another QIB with respect to which it exercises sole
      investment discretion and to whom it has given notice that the 9.75%
      Senior Notes are being sold in reliance on Rule 144A.

                (3)  Such purchaser acknowledges that none of the Company, the
      Guarantor or the Initial Purchasers, or any person representing the
      Company, the Guarantor or the Initial Purchasers, has made any
      representation to it with respect to the Company, the Guarantor or the
      offering or sale of any 9.75% Senior Notes other than the information
      contained in the Offering Memorandum, which has been delivered to it and
      upon which such purchaser is relying in making its investment decision
      with respect to the 9.75% Senior Notes.  Accordingly, such purchaser
      acknowledges that no representation or warranty is made by the Initial
      Purchasers as to the accuracy or completeness of such materials.  Such
      purchaser has had access to such financial and other information
      concerning the Company, the Guarantor and the 9.75% Senior Notes (and
      the Guarantees) as it has deemed necessary in connection with its
      decision to purchase any of the 9.75% Senior Notes, including an
      opportunity to ask questions of and request information from the Initial
      Purchasers, the Company and the Guarantor.

                (4)  Such purchaser is purchasing the 9.75% Senior Notes for
      its own account, or for one or more investor accounts for which it is
      acting as a fiduciary or agent, in each case for investment, and not
      with a view to, or for offer or sale in connection with, any
      distribution thereof in violation of the Securities Act, subject to any
      requirement of law that the disposition of its property or the property
      of such investor account or accounts be at all times within its or their
      control and subject to its or their ability to resell such 9.75% Senior
      Notes pursuant to Rule 144A or any exemption from registration available
      under the Securities Act or pursuant to a registration statement which
      has been declared effective under the Securities Act.  Such purchaser
      agrees on its own behalf and on behalf of any investor account for which
      it is purchasing the 9.75% Senior Notes, and each subsequent holder of
      the 9.75% Senior Notes by its acceptance thereof will be deemed to
      agree, to offer, sell or otherwise transfer the 9.75% Senior Notes prior
      to (x) the date which is two years (or such shorter period of time as
      permitted by Rule 144(k) under the Securities Act) after the later of
      the date of original issue of the 9.75% Senior Notes and the last date
      on which the Company or any of its "affiliates" (as defined in Rule 144
      under the Securities Act) was the owner of the 9.75% Senior Notes (or
      any predecessor thereto) or (y) such later date, if any, as may be
      required by applicable law (the "Resale Restriction Termination Date"),
      only (a) to the Company, (b) pursuant to a registration statement which
      has been declared effective under the Securities Act, (c) for so long as
      the 9.75% Senior Notes are eligible for resale pursuant to Rule 144A to
      a person it reasonably believes is a QIB that purchases for its own
      account or for the account of a QIB, in each case to whom notice is
      given that the transfer is being made in reliance on Rule 144A or (d)

<PAGE>

      pursuant to any other available exemption from the registration
      requirements of the Securities Act, subject in each of the foregoing
      cases to any requirement of law that the disposition of its property or
      the property of such investor account or accounts be at all times within
      its or their control and to compliance with any applicable state or
      other securities laws.  The foregoing restrictions on resale will not
      apply subsequent to the Resale Restriction Termination Date.  Each
      purchaser of 9.75% Senior Notes acknowledges that the Company, the
      Guarantor and the Trustee reserve the right prior to any offer, sale or
      other transfer of 9.75% Senior Notes prior to the Resale Restriction
      Termination Date pursuant to clauses (d), above, to require the delivery
      of an opinion of counsel, certifications and/or other information
      satisfactory to them and the Trustee.  Each purchaser of 9.75% Senior
      Notes acknowledges that each 9.75% Senior Note will contain a legend
      substantially in the form on the face of this Senior Note unless
      otherwise agreed by the Company, the Guarantor and the Trustee.

                (5)  Such purchaser acknowledges that the Company, the
      Guarantor, the Initial Purchasers, the Trustee and others will rely upon
      the truth and accuracy of the foregoing acknowledgments, representations
      and agreements and agree that, if any of the acknowledgments,
      representations, warranties and agreements deemed to have been made by
      its purchase of the notes are no longer accurate, it shall promptly
      notify the Initial Purchasers.  If such purchaser is acquiring any notes
      as a fiduciary or agent for one or more investor accounts, it represents
      that it has sole investment discretion with respect to each such account
      and it has full power to make the foregoing acknowledgments,
      representations and agreements on behalf of each such account and that
      each such investor account is eligible to purchase the notes.

                (6)  Such purchaser acknowledges that the Trustee, the
      transfer agent and the registrar will not be required to accept for
      registration of transfer any notes acquired by it, except upon
      presentation of evidence satisfactory to the Company and the Trustee
      that the restrictions set forth above have been complied with.

                (7)  Such purchaser acknowledges that the foregoing
      restrictions apply to holders of beneficial interests in the 9.75%
      Senior Notes, as well as the holders of the 9.75% Senior Notes.

           The 9.75% Senior Notes do not have the benefit of any sinking fund
obligations and shall not be repayable at the option of the Holder prior to
maturity.

           The 9.75% Senior Notes may be redeemed at the Company's option, in
whole or in part, at any time on at least 30 days', but not more than 60
days', prior written notice mailed to the registered holders of the 9.75%
Senior Notes, at a price equal to the greater of (a) 100% of the principal
amount of the 9.75% Senior Notes being redeemed and (b) the sum of the
present values of the principal amount of the 9.75% Senior Notes to be
redeemed and the remaining scheduled payments of interest on the 9.75% Senior
Notes from the redemption date to January 15, 2013, discounted from their
respective scheduled payment dates to the redemption date semi-annually
(assuming a 360-day year consisting of twelve 30-day months) at a discount
rate equal to the equivalent yield to maturity of a comparable treasury
security plus 50 basis points, plus accrued interest on the 9.75% Senior
Notes to the redemption date.

           If an Event of Default with respect to the 9.75% Senior Notes shall
occur and be continuing, the principal of all the 9.75% Senior Notes may be
declared due and payable in the manner and with the effect provided in the
Indenture.

           The Indenture contains provisions for defeasance at any time of (a)
the entire indebtedness of the Company (and the Guarantor) under this Senior
Note and (b) certain restrictive covenants and the related defaults and
Events of Default with respect to the 9.75% Senior Notes applicable to the
Company and the Guarantor, in each case, upon compliance by the Company and
the Guarantor with certain conditions set forth in the Indenture, which
provisions apply to this Senior Note.

           The Indenture permits, with certain exceptions as therein provided,
the amendment thereof and the modification of the rights and obligations of
the Company and the Guarantor and the rights of the Holders of the 9.75%
Senior Notes under the Indenture at any time by the Company, the Guarantor
and the Trustee with the consent of the Holders of a majority in aggregate
principal amount of the 9.75% Senior Notes at the time outstanding.  The

<PAGE>

Indenture also contains provisions permitting the Holders of specified
percentages in aggregate principal amount of the 9.75% Senior Notes at the
time outstanding, on behalf of the Holders of all 9.75% Senior Notes, to
waive compliance by the Company and the Guarantor with certain provisions of
the Indenture and certain past Defaults under the Indenture and their
consequences.  Any such consent or waiver by the Holder of this Senior Note
shall be conclusive and binding upon such Holder and upon all future Holders
of this Senior Note and of any 9.75% Senior Notes issued upon the
registration of transfer thereof or in exchange herefor or in lieu hereof,
whether or not notation of such consent or waiver is made upon this Senior
Note.

           No reference herein to the Indenture and provision of this Senior
Note or of the Indenture shall alter or impair the obligation of the Company
and the Guarantor, which is absolute and unconditional, to pay the principal
of (and premium, if any) and interest on this Senior Note at the times, place
and rate, and in the coin or currency, herein prescribed.

           As provided in the Indenture and subject to certain limitations on
transfer of this Senior Note by DTC or its nominee, the transfer of this
Senior Note is registrable by the Registrar, upon surrender of this Senior
Note for registration of transfer at the office or agency of the Company or
the Guarantor, as the case may be, in St. Paul, Minnesota and the Borough of
Manhattan, The City of New York, New York, duly endorsed by, or accompanied
by the written instrument of transfer attached hereto duly executed by the
Holder hereof or his attorney duly authorized in writing, and thereupon one
or more new 9.75% Senior Notes, of authorized denominations and for the same
aggregate principal amount, shall be issued to the designated transferee or
transferees.

           The 9.75% Senior Notes are issuable only in fully registered form
without coupons in denominations of $1,000 and any integral multiple
thereof.  As provided in the Indenture and subject to certain limitations
therein set forth, the 9.75% Senior Notes are exchangeable for a like
aggregate principal amount of 9.75% Senior Notes of different authorized
denomination, as requested by the Holder surrendering the same.

           No service charge shall be made for any such registration of
transfer or exchange of 9.75% Senior Notes, but the Company and the Guarantor
may require payment of a sum sufficient to cover any tax or other
governmental charge payable in connection therewith.

           Prior to due presentment of this Senior Note for registration of
transfer, the Company, the Guarantor, the Trustee and any agent of the
Company, the Guarantor or the Trustee may treat the person in whose name this
Senior Note is registered as the owner hereof for all purposes, whether or
not this Senior Note be overdue, and none of the Company, the Guarantor, the
Trustee or any such agent shall be affected by notice to the contrary.

           Interest on this Senior Note shall be computed on the basis of a
360-day year of twelve 30-day months.

           The Company shall furnish to any Holder of record of 9.75% Senior
Notes, upon written request and without charge, a copy of the Indenture.

           The Indenture and this Senior Note each shall be governed by and
construed in accordance with the laws of the State of Wisconsin without
regard to principles of conflicts of law.

           Unless the certificate of authentication hereon has been executed
by the Trustee by manual signature, this Senior Note shall not be entitled to
any benefit under the Indenture or be valid or obligatory for any purpose.



          [the rest of this page has INTENTIONALLY been left blank.]


<PAGE>


           In Witness Whereof, Alliant Energy Resources, Inc. has caused this
9.75% Senior Note to be signed in its corporate name by the facsimile
signature of two of its officers thereunto duly authorized and has caused a
facsimile of its corporate seal to be affixed hereto or imprinted or
otherwise reproduced hereon.

      ATTEST:                             ALLIANT ENERGY RESOURCES, INC.





      By:  _________________________      By:  ________________________________
           Name:                               Name:
           Title:                              Title:


<PAGE>

           FOR VALUE RECEIVED, the Guarantor, hereby unconditionally
guarantees to the Holder of the Security upon which this Guarantee is
endorsed the due and punctual payment of the principal, of premium, if any,
or interest on said Security, when and as the same shall be become due and
payable, whether at maturity, upon redemption or otherwise, according to the
terms thereof and of the Indenture referred to therein.

           The Guarantor agrees to determine, at least one business day prior
to the date upon which a payment of principal, of premium, if any, or
interest on said Security is due and payable, whether the Company has
available the funds to make such payment as the same shall become due and
payable.  In case of the failure of the Company punctually to pay any such
principal, premium, if any, or interest, the Guarantor hereby agrees to cause
any such payment to be made punctually when and as the same shall become due
and payable, whether at maturity, upon redemption or otherwise, and as if
such payment were made by the Company.

           The Guarantor hereby agrees that its obligations hereunder shall be
unconditional, irrevocable and absolute, irrespective of the validity,
regularity or enforceability of said Security or said Indenture, the absence
of any action to enforce the same, any waiver or consent by the Holder of
said Security with respect to any  provisions thereof, the recovery of any
judgment against the Company or any action to enforce the same or any other
circumstance which might otherwise constitute a legal or equitable discharge
or defense of a guarantor.  The Guarantor hereby waives diligence,
presentment, demand of payment, filing of claims with a court in the event of
merger or bankruptcy of the Company, any right to require a proceeding first
against the Company, protest or notice with respect to said Security or
indebtedness evidenced thereby, and all demands whatsoever and covenants that
this Guarantee will not be discharged except by complete performance of the
obligations contained in said Security and in this Guarantee.

           The Guarantor shall be subrogated to all rights of the Holder of
said Security against the Company in respect to any amounts paid by the
Guarantor pursuant to the provisions of this Guarantee; provided, however,
that the Guarantor shall not, without the consent of the Holders of all of
the Securities then outstanding, be entitled to enforce or to receive any
payments arising out of or based upon such right of subrogation until the
principal of and premium, if any, and interest on all Securities shall have
been paid in full or payment thereof shall have been provided for in
accordance with said Indenture.

           Notwithstanding anything to the contrary contained herein, if
following any payment of principal or interest by the Company on the
Securities to the Holders of the Securities it is determined by a final
decision of a court of competent jurisdiction that such payment shall be
avoided by a trustee in bankruptcy (including any debtor-in-possession) as a
preference under 11 U.S.C. Section 547 and such payment is paid by such
Holder to such trustee in bankruptcy, then and to the extent of such
repayment the obligations of the Guarantor hereunder shall remain in full
force and effect.

           This Guarantee shall not be valid or become obligatory for any
purpose with respect to a Security until a certificate of authentication on
such Security shall have been signed by the Trustee (or the authenticating
agent).

           This Guarantee shall be governed by the laws of the State of
Wisconsin.


<PAGE>


           IN WITNESS WHEREOF, ALLIANT ENERGY CORPORATION has caused this
Guarantee to be signed in its corporate name by the signature of two of its
officers thereunto duly authorized and has caused its corporate seal to be
affixed hereto or imprinted or otherwise reproduced hereon.



                                          ALLIANT ENERGY CORPORATION,
      ATTEST:                             as Guarantor





      By:  _________________________      By:  ________________________________
           Name:                               Name:
           Title:                              Title:




<PAGE>


                     TRUSTEE CERTIFICATE OF AUTHENTICATION
                     -------------------------------------



           This is one of the 9.75% Senior Notes described in the within-named
Indenture.



                                    U.S. BANK NATIONAL ASSOCIATION,
                                    as Trustee





                                    By:  ________________________________
                                         Name:
                                         Title:



<PAGE>

                                                                      EXHIBIT B
                          EXHIBIT H TO THE INDENTURE

                        FORM OF INCURRENCE CERTIFICATE



TO:   U.S. BANK NATIONAL ASSOCIATION

           Reference is hereby made to the Fourth Supplemental Indenture,
dated as of December 26, 2002 (the "Fourth Supplemental Indenture"), among
Alliant Energy Resources, Inc., a Wisconsin corporation (the "Company"),
Alliant Energy Corporation, a Wisconsin corporation, as guarantor (the
"Guarantor"), and U.S. Bank National Association, as successor to Firstar
Bank, N.A., as Trustee.  Terms with initial capital letters used but not
defined herein have the meanings assigned to them in the Fourth Supplemental
Indenture.

           This Incurrence Certificate is being delivered pursuant to
Section 2.08 of the Fourth Supplemental Indenture and relates to [description
of new Indebtedness] (the "New Indebtedness") by the [Company/Guarantor/name
of Consolidated Subsidiary] incurred on [date New Indebtedness is incurred]
(the "Incurrence Date").  The undersigned are the _________________________
and the __________________________, respectively, of the Guarantor and each
hereby certifies as of the date hereof, in his capacity as officer of the
Guarantor, as follows:

           As of the Incurrence Date, after giving pro forma effect to the
incurrence of the New Indebtedness:

           (a)  Consolidated Net Worth is more than $1.2 billion;

           (b)  the ratio of Consolidated Indebtedness to Consolidated Total
Capitalization does not exceed 0.70 to 1.00; and

           (c)  the Interest Coverage Ratio is more than 2.0 to 1.0.

           Schedule I attached hereto sets forth the calculations performed by
the undersigned in order to make the foregoing certifications.

           IN WITNESS WHEREOF, each of the undersigned has hereunto set his
hand this __ day of _______, 20__.


                               ______________________________________
                               Name:
                               Title:


                               ______________________________________
                               Name:
                               Title:

<PAGE>

                                  SCHEDULE I

             [CALCULATIONS USED TO PROVIDE INCURRENCE CERTIFICATE]