ALLIANT ENERGY CORP
S-4/A, 2000-04-25
ELECTRIC & OTHER SERVICES COMBINED
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<PAGE>   1


     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL 25, 2000


                                                      REGISTRATION NO. 333-92859
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549
                            ------------------------

                                AMENDMENT NO. 3

                                       TO
                                    FORM S-4
                             REGISTRATION STATEMENT
                                     Under
                           THE SECURITIES ACT OF 1933
                            ------------------------
                    Issuer of Senior Notes registered hereby
                         ALLIANT ENERGY RESOURCES, INC.
             (Exact name of registrant as specified in its charter)
                            ------------------------

<TABLE>
<S>                              <C>                              <C>
           WISCONSIN                          6719                          39-1605561
(State or other jurisdiction of   (Primary Standard Industrial    (I.R.S. Employer Identification
         incorporation)            Classification Code Number)                 No.)
</TABLE>

                              ALLIANT ENERGY TOWER
                              200 FIRST STREET SE
                            CEDAR RAPIDS, IOWA 52401
                                 (319) 398-4411
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)

                  Guarantor of Senior Notes registered hereby
                           ALLIANT ENERGY CORPORATION
            (Exact name of registration as specified in its charter)

<TABLE>
<S>                              <C>                              <C>
           WISCONSIN                          6719                          39-1380265
(State or other jurisdiction of   (Primary Standard Industrial    (I.R.S. Employer Identification
         incorporation)            Classification Code Number)                 No.)
</TABLE>

                           222 WEST WASHINGTON AVENUE
                            MADISON, WISCONSIN 53703
                                 (608) 252-3311
  (Address, including zip code, and telephone number, including area code, of
                   registrant's principal executive offices)

<TABLE>
<S>                                              <C>
               EDWARD M. GLEASON                                   Copies to:
    VICE PRESIDENT-TREASURER AND CORPORATE                BENJAMIN F. GARMER, III, ESQ.
                    SECRETARY                                    FOLEY & LARDNER
        ALLIANT ENERGY RESOURCES, INC.                      777 EAST WISCONSIN AVENUE
          ALLIANT ENERGY CORPORATION                       MILWAUKEE, WISCONSIN 53202
          222 WEST WASHINGTON AVENUE                             (414) 271-2400
           MADISON, WISCONSIN 53703
                (608) 252-3311
    (Name, address, including zip code, and
                telephone number,
  including area code, of agent for service)
</TABLE>

                            ------------------------
     APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: Upon
consummation of the Exchange Offer referred to herein.

     If the securities being registered on this Form are being offered in
connection with the formation of a holding company and there is compliance with
General Instruction G, check the following box.  [ ]

     If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, check the following box and
list the Securities Act registration statement number of the earlier effective
registration statement for the same offering.  [ ]

     If this Form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ]
                            ------------------------
     THE REGISTRANTS HEREBY AMEND THIS REGISTRATION STATEMENT ON SUCH DATE OR
DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANTS
SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION
STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF
THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A),
MAY DETERMINE.
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   2

     THE INFORMATION IN THIS PROSPECTUS IS NOT COMPLETE AND MAY BE CHANGED. WE
     MAY NOT SELL THESE SECURITIES UNTIL THE REGISTRATION STATEMENT FILED WITH
     THE SECURITIES AND EXCHANGE COMMISSION IS EFFECTIVE. THIS PROSPECTUS IS NOT
     AN OFFER TO SELL THESE SECURITIES AND IT IS NOT SOLICITING AN OFFER TO BUY
     THESE SECURITIES IN ANY STATE WHERE THE OFFER OR SALE IS NOT PERMITTED.


                  SUBJECT TO COMPLETION, DATED APRIL 25, 2000


                       [ALLIANT ENERGY RESOURCES, INC. LOGO]

                         ALLIANT ENERGY RESOURCES, INC.
                               OFFER TO EXCHANGE
                                ALL OUTSTANDING
                          7 3/8% SENIOR NOTES DUE 2009
                   $250,000,000 PRINCIPAL AMOUNT OUTSTANDING
                                      FOR
                        NEW 7 3/8% SENIOR NOTES DUE 2009
                         $250,000,000 PRINCIPAL AMOUNT
                             ----------------------
- -  We are offering to exchange new registered 7 3/8% Senior Notes due 2009 for
   all of our outstanding unregistered 7 3/8% Senior Notes due 2009.

- -  The exchange offer expires at 5:00 p.m., New York City time, on
                , 2000, unless we extend it.

- -  The terms of the new senior notes are substantially identical to those of the
   existing senior notes, except that the new senior notes will not have
   securities law transfer restrictions and registration rights relating to the
   existing senior notes and the new senior notes will not provide for the
   payment of additional interest under circumstances relating to the timing of
   the exchange offer.

- -  Our parent, Alliant Energy Corporation, will fully and unconditionally
   guarantee the new senior notes.

- -  The exchange offer is not subject to any condition other than that the
   exchange offer not violate applicable law or applicable interpretation of the
   staff of the SEC and certain other conditions.

- -  All outstanding senior notes that are validly tendered and not validly
   withdrawn will be exchanged.

- -  You may withdraw your tender of existing senior notes any time before the
   exchange offer expires.

- -  We will not receive any proceeds from the exchange offer.

- -  The exchange of senior notes will not be a taxable event for U.S. federal
   income tax purposes.

   Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

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

              The date of this prospectus is              , 2000.
<PAGE>   3

<PAGE>   4

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                PAGE
                                                                ----
<S>                                                             <C>
Prospectus Summary..........................................       4
Where You Can Find More Information.........................      13
Forward-Looking Statements..................................      14
Use of Proceeds.............................................      15
Capitalization..............................................      15
The Exchange Offer..........................................      16
Business....................................................      25
Description of Outstanding Indebtedness.....................      28
Description of the New Senior Notes.........................      29
United States Federal Income Tax Considerations.............      43
Plan of Distribution........................................      46
Legal Matters...............................................      47
Experts.....................................................      47
</TABLE>

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

                                        3
<PAGE>   5

                               PROSPECTUS SUMMARY

     The following summary highlights selected information from this prospectus
and may not contain all of the information that is important to you. This
prospectus includes the specific terms of the new senior notes we are offering,
as well as information regarding our business. We encourage you to read this
prospectus in its entirety.

                         ALLIANT ENERGY RESOURCES, INC.

     We are a wholly-owned subsidiary of Alliant Energy Corporation, which is a
registered public utility holding company. We manage a portfolio of companies
involved in non-regulated businesses.

     Through these businesses, we:

     -  offer large energy users an array of services to maximize their
        productivity and energy efficiency,

     -  provide solutions for waste remediation and other environmental
        engineering and consulting services,

     -  make investments in utilities in international and domestic markets and
        seek opportunities to develop or improve electricity generation
        facilities in these markets,

     -  market new products and services to enhance the security and comfort of
        residential and small customers and to maximize their energy efficiency,

     -  buy, sell and trade electricity for large customers and assist those
        customers to minimize risks related to changes in costs of energy
        through Cargill-Alliant LLC, a joint venture with Cargill Incorporated
        in which we have a 50% ownership interest,

     -  offer short-line railway freight service in Iowa, storage services and
        barge terminal and hauling service on the Mississippi River, and

     -  own, manage and develop affordable housing developments and provide
        equity and debt financing for these developments.

     Set forth below is a condensed organization chart that reflects how our and
Alliant Energy Corporation's businesses and investments are managed:

                                    [GRAPH]

     Our principal executive offices are located at Alliant Tower, 200 First
Street SE, Cedar Rapids, Iowa 52401, telephone number (319) 398-4411.
                                        4
<PAGE>   6

                           ALLIANT ENERGY CORPORATION

     Alliant Energy Corporation was formed as a result of a three-way merger
involving WPL Holdings, Inc., IES Industries Inc. and Interstate Power Company.
The merger was completed in April 1998. The first tier subsidiaries of Alliant
Energy Corporation include Wisconsin Power and Light Company, IES Utilities
Inc., Interstate Power Company, Alliant Energy Resources, Inc. and Alliant
Energy Corporate Services, Inc.

     Alliant Energy Corporation, through its public utility operating companies,
Wisconsin Power and Light Company, IES Utilities Inc. and Interstate Power
Company, is engaged principally in:

     -  the generation, transmission, distribution and sale of electric energy;

     -  the purchase, distribution, transportation and sale of natural gas; and

     -  the provision of water and steam services in selected markets.

The principal markets of Alliant Energy Corporation's utility operating
subsidiaries are located in Iowa, Wisconsin, Minnesota and Illinois. Alliant
Energy Corporation is also involved in several non-regulated and non-utility
activities through our company.

     Alliant Energy Corporation, a public utility holding company incorporated
in Wisconsin in 1981, has its principal executive offices located at 222 West
Washington Avenue, Madison, Wisconsin 53703, telephone number (608) 252-3311.

                               THE EXCHANGE OFFER

Existing Senior Notes......  We sold $250,000,000 of our 7 3/8% Senior Notes due
                             2009, which are fully and unconditionally
                             guaranteed by Alliant Energy Corporation, to the
                             initial purchasers on November 9, 1999. We issued
                             the existing senior notes at a discount of 1.2% per
                             existing senior note, which means the initial
                             purchasers paid less than the principal amount for
                             the existing senior notes. The initial purchasers
                             resold those existing senior notes to qualified
                             institutional buyers pursuant to Rule 144A under
                             the Securities Act of 1933.

Registration Rights
Agreement..................  When we sold the existing senior notes we entered
                             into a registration rights agreement with the
                             initial purchasers in which we agreed, among other
                             things, to provide to you and all other holders of
                             these existing senior notes the opportunity to
                             exchange your unregistered existing senior notes
                             for a new series of substantially identical new
                             senior notes that we have registered under the
                             Securities Act. This exchange offer is being made
                             for that purpose.

New Senior Notes...........  We are offering registered 7 3/8% Senior Notes due
                             2009, which are fully and unconditionally
                             guaranteed by Alliant Energy Corporation, in
                             exchange for your existing senior notes. The terms
                             of the new senior notes and the existing senior
                             notes are substantially identical except:

                             -  the new senior notes will be issued in a
                                transaction that will have been registered under
                                the Securities Act;

                             -  the new senior notes will not contain securities
                                law restrictions on transfer; and

                             -  the new senior notes will not provide for the
                                payment of additional interest under
                                circumstances relating to the timing of the
                                exchange offer.

                                        5
<PAGE>   7

The Exchange Offer.........  We are offering to exchange $1,000 principal amount
                             of the new senior notes for each $1,000 principal
                             amount of your existing senior notes. As of the
                             date of this prospectus, $250,000,000 aggregate
                             principal amount of the existing senior notes are
                             outstanding. For procedures for tendering, see "The
                             Exchange Offer -- Procedures for Tendering Existing
                             Senior Notes"

Expiration Date............  This exchange offer will expire at 5:00 p.m., New
                             York City time, on             , 2000, unless we
                             extend it.

Resales of New Senior
Notes......................  We believe that you may resell or otherwise
                             transfer the new senior notes received in the
                             exchange offer without complying with the
                             registration and prospectus delivery provisions of
                             the Securities Act so long as you are not a
                             broker-dealer and you meet the following
                             conditions:

                             -  you are not our "affiliate" within the meaning
                                of Rule 405 under the Securities Act;

                             -  you acquire the new senior notes issued in the
                                exchange offer in the ordinary course of your
                                business;

                             -  you have no arrangement or understanding with
                                any person to participate in the distribution of
                                the new senior notes; and

                             -  you did not purchase the existing senior notes
                                directly from us to resell pursuant to Rule 144A
                                or any other available exemption from the
                                Securities Act.

                             By signing the letter of transmittal and tendering
                             your existing senior notes, you will be making
                             representations to this effect. You may incur
                             liability under the Securities Act if:

                             -  any of the representations listed above are not
                                true; and

                             -  you transfer any new senior note issued to you
                                in the exchange offer without either delivering
                                a prospectus meeting the requirements of the
                                Securities Act or qualifying for an exemption
                                from the registration requirements under the
                                Securities Act.

                             We do not assume or indemnify you against liability
                             under these circumstances, which means that we will
                             not protect you against any loss incurred as a
                             result of this liability under the Securities Act.

                             If you do not meet the conditions listed above,
                             then:

                             -  you will not be permitted to tender existing
                                senior notes in the exchange offer; and

                             -  you must comply with the registration and
                                prospectus delivery requirements of the
                                Securities Act, including being named as a
                                selling security holder, in connection with any
                                sale of existing senior notes unless an
                                exemption from these requirements is available.

                             Each broker-dealer that has received new senior
                             notes for its own account in exchange for existing
                             senior notes that were acquired as a result of
                             market-making or other trading activities must
                             acknowledge that it will deliver a prospectus
                             meeting the requirements of the Securities Act in
                             connection with any resale of the new senior notes.

                                        6
<PAGE>   8

                             A broker-dealer generally may use this prospectus
                             in connection with any such resale. See "The
                             Exchange Offer -- Resales of New Senior Notes."

Acceptance of Existing
Senior Notes and Delivery
  of New Senior Notes......  We will accept for exchange any and all existing
                             senior notes that are validly tendered in the
                             exchange offer and not withdrawn before the offer
                             expires. The new senior notes will be delivered
                             promptly following the exchange offer.

Withdrawal Rights..........  You may withdraw your tender of existing senior
                             notes at any time before the exchange offer
                             expires.

Conditions of the Exchange
Offer......................  The exchange offer is subject to the following
                             conditions, which we may waive:

                             -  the exchange offer, or the making of any
                                exchange by a holder of existing senior notes,
                                will not violate any applicable law or
                                interpretation by the staff of the SEC; and

                             -  no action may be pending or threatened in any
                                court or before any governmental agency with
                                respect to the exchange offer that may impair
                                our ability to proceed with the exchange offer.

Consequences of Failure to
  Exchange.................  If you are eligible to participate in the exchange
                             offer and you do not tender your existing senior
                             notes, then you will not have further exchange or
                             registration rights and you will continue to hold
                             existing senior notes subject to restrictions on
                             transfer.

Federal Income Tax
  Consequences.............  The exchange of an existing senior note for a new
                             senior note will not be taxable to a United States
                             holder for federal income tax purposes.
                             Consequently, you will not recognize any gain or
                             loss upon receipt of the new senior notes. See
                             "United States Federal Income Tax Considerations."

Use of Proceeds............  We will not receive any proceeds from the exchange
                             offer.

Accounting Treatment.......  We will not recognize any gain or loss on the
                             exchange of senior notes. See "The Exchange
                             Offer -- Accounting Treatment."

Exchange Agent.............  Firstar Bank, N.A. is the exchange agent. See "The
                             Exchange Offer -- Exchange Agent."

                                        7
<PAGE>   9

                              THE NEW SENIOR NOTES

     The new senior notes will evidence the same debt as the existing senior
notes and will be governed by the same indenture, as supplemented, under which
the existing senior notes were issued.

TERMS OF THE NEW SENIOR NOTES

Aggregate Principal
Amount.....................  Up to $250,000,000.

Interest Rate..............  7 3/8% per year.

Maturity Date..............  November 9, 2009.


Interest Payment Dates.....  May 9 and November 9 of each year, beginning
                             November 9, 2000.


Interest Calculations......  Based on a 360-day year of twelve 30-day months.

Parent Company Guarantee...  Our parent, Alliant Energy Corporation, will fully
                             and unconditionally guarantee the new senior notes.
                             The guarantee will be equal in right of payment
                             with all other unsecured indebtedness and
                             guarantees issued by Alliant Energy Corporation.
                             The guarantee will be effectively subordinated to
                             all secured indebtedness of Alliant Energy
                             Corporation and will be effectively subordinated to
                             the claims of creditors of any of Alliant Energy
                             Corporation's subsidiaries. As of December 31,
                             1999, the amount of indebtedness of Alliant Energy
                             Corporation that ranked equally with, or senior to,
                             the guarantee was $309.8 million, none of which was
                             secured.

Ranking....................  The new senior notes will rank equally with all of
                             our other unsecured and unsubordinated
                             indebtedness. The new senior notes will be
                             effectively subordinated to all of our secured
                             indebtedness and will be effectively subordinated
                             to the claims of creditors of any of our
                             subsidiaries. As of December 31, 1999, as adjusted
                             to give effect to the issuance of our exchangeable
                             senior notes due 2030 in the initial aggregate
                             principal amount of $402.5 million on February 1,
                             2000, the amount of indebtedness of Alliant Energy
                             Resources that ranked equally with, or senior to,
                             the senior notes was $789.8 million, none of which
                             was secured. As of December 31, 1999, the amount of
                             indebtedness incurred by our subsidiaries was $80.1
                             million.

Ratings....................  The senior notes have been assigned ratings of A by
                             Standard & Poor's Ratings Services and A3 by
                             Moody's Investor's Service, Inc. These ratings have
                             been obtained with the understanding that S&P and
                             Moody's will continue to monitor our credit rating
                             and that of Alliant Energy Corporation, and will
                             make future adjustments to the extent warranted. A
                             rating reflects only the views of S&P or Moody's
                             and is not a recommendation to buy, sell or hold
                             the senior notes. We cannot give any assurance that
                             the ratings will be retained for any time period or
                             that they will not be revised downward or withdrawn
                             entirely by S&P or Moody's.

                                        8
<PAGE>   10

Optional Redemption........  The new senior notes will be redeemable in whole or
                             in part at our option at any time, on at least 30
                             days' but not more than 60 days' prior written
                             notice at a price equal to the greater of:

                             - 100% of the principal amount of the new senior
                               notes being redeemed and

                             - the sum of the present values of the principal
                               amount of the new senior notes to be redeemed and
                               the remaining scheduled payments of interest on
                               the new senior notes from the redemption date to
                               November 9, 2009, discounted from their
                               respective scheduled payment dates to the
                               redemption date semi-annually at a discount rate
                               equal to the Treasury Yield, as defined under
                               "Description of the New Senior Notes -- Optional
                               Redemption", plus 20 basis points, plus accrued
                               interest on the senior notes to the redemption
                               date. See "Description of the New Senior Notes --
                               Optional Redemption."

Sinking Fund...............  None.

Form and Denominations.....  The new senior notes initially will be issued in
                             fully registered book-entry form and will be
                             represented by one or more registered global
                             securities deposited with or on behalf of, and
                             registered in the name of, a nominee of The
                             Depository Trust Company. The new senior notes will
                             be issued in denominations of $1,000 and integral
                             multiples thereof.

Absence of Market for the
Notes......................  The new senior notes are a new issue of securities
                             with no established trading market. We currently
                             have no intention to apply to list the new senior
                             notes on any securities exchange or to seek their
                             admission to trading on any automated quotation
                             system. Accordingly, we cannot provide any
                             assurance as to the development or liquidity of any
                             market for the new senior notes.

GENERAL INDENTURE PROVISIONS APPLICABLE TO THE NEW SENIOR NOTES

No Limit on Debt...........  The indenture governing the new senior notes does
                             not limit the amount of debt that we may issue or
                             provide holders any protection should we be
                             involved in a highly leveraged transaction.

Covenants..................  The indenture contains covenants that, among other
                             things, will limit our ability and that of our
                             subsidiaries and, for some limited matters, Alliant
                             Energy Corporation to:

                             -  issue, assume or guarantee some types of secured
                                indebtedness;

                             -  engage in sale and lease-back transactions; and

                             -  consolidate or merge.

                             These covenants are subject to important exceptions
                             and qualifications, which are described under the
                             heading "Description of the New Senior
                             Notes -- Covenants" in this prospectus.

                                        9
<PAGE>   11

Events of Default..........  Each of the following is an event of default under
                             the indenture:

                             -  the failure by us or Alliant Energy Corporation
                                to pay principal of or premium, if any, on the
                                senior notes when due;

                             -  the failure by us or Alliant Energy Corporation
                                for 30 days to pay interest when due on the
                                senior notes;

                             -  the failure by us or Alliant Energy Corporation
                                to perform other covenants with respect to the
                                senior notes following 90 days after receipt of
                                notice of failure; and

                             -  events of bankruptcy, insolvency or
                                reorganization of us or Alliant Energy
                                Corporation.

                             These covenants are subject to important exceptions
                             and qualifications, which are described under the
                             heading "Description of the New Senior
                             Notes -- Events of Default" in this prospectus.

Remedies...................  If any event of default occurs and is continuing,
                             the trustee under the indenture or holders of at
                             least 25% in aggregate principal amount of
                             outstanding senior notes may declare the principal
                             thereof immediately due and payable.

Other......................  The new senior notes and the existing senior notes
                             will vote together as a single class for purposes
                             of determining whether the holders of the requisite
                             percentage in outstanding principal amount have
                             taken certain actions or exercised certain rights
                             under the indenture.

                                       10
<PAGE>   12

                         SUMMARY FINANCIAL INFORMATION

ALLIANT ENERGY RESOURCES, INC.

     The following table sets forth our unaudited summary consolidated financial
information. The information set forth below was derived from Alliant Energy
Corporation's financial statements and notes.

<TABLE>
<CAPTION>
                                                                    YEAR ENDED DECEMBER 31,
                                                                --------------------------------
                                                                  1999        1998        1997
                                                                --------    --------    --------
                                                                         (IN THOUSANDS)
<S>                                                             <C>         <C>         <C>
INCOME STATEMENT DATA:
Operating revenues..........................................    $305,029    $238,676    $361,961
Operating income (loss).....................................      (1,256)     (8,608)     (6,818)
Net income (loss)...........................................      37,812(1)   (8,898)     (3,966)
</TABLE>

<TABLE>
<CAPTION>
                                                                     DECEMBER 31,
                                                                ----------------------
                                                                   1999         1998
                                                                ----------    --------
                                                                    (IN THOUSANDS)
<S>                                                             <C>           <C>
BALANCE SHEET DATA:
Current assets..............................................    $  132,401    $ 92,148
Non-current assets(2).......................................     1,716,148     777,113
Current liabilities.........................................       197,669      63,648
Non-current liabilities (excludes minority interest)........       502,760     160,278
Minority interest(3)........................................         7,208       6,193
</TABLE>

- ---------------
(1) Includes after-tax gains of $25 million from the sales of a portion of our
    investment in McLeodUSA Incorporated.

(2) Includes the market value of McLeodUSA Incorporated of $1,124 million at
    December 31, 1999 and $320 million at December 31, 1998.

(3) Minority interest represents primarily real estate joint ventures.

                                       11
<PAGE>   13

ALLIANT ENERGY CORPORATION

     The following table sets forth selected consolidated financial information
of Alliant Energy Corporation. The information set forth below was selected or
derived from the financial statements and notes of Alliant Energy Corporation.
The information set forth below is qualified in its entirety by and should be
read in conjunction with the Alliant Energy Corporation Management's Discussion
and Analysis of Financial Condition and Results of Operations and the detailed
information and consolidated financial statements, including the notes thereto,
incorporated by reference in this prospectus. See "Where You Can Find More
Information."

<TABLE>
<CAPTION>
                                                           YEAR ENDED DECEMBER 31,
                                      ------------------------------------------------------------------
                                         1999        1998(1)         1997          1996          1995
                                      ----------    ----------    ----------    ----------    ----------
                                               (DOLLARS IN THOUSANDS EXCEPT FOR PER SHARE DATA)
<S>                                   <C>           <C>           <C>           <C>           <C>
INCOME STATEMENT DATA:
Operating revenues..................  $2,197,963    $2,130,874    $2,300,627    $2,232,840    $1,976,807
Operating income....................     376,535       283,302       336,383       365,439       364,932
Income from continuing operations...     196,581        96,675       144,578       157,088       159,157
Net income..........................     196,581        96,675       144,578       155,791       145,971
PER SHARE DATA:
Income from continuing operations...       $2.51         $1.26         $1.90         $2.08         $2.13
Earnings per average common share
  (basic and diluted)...............       $2.51         $1.26         $1.90         $2.06         $1.95
Dividends declared per common
  share(2)..........................       $2.00         $2.00         $2.00         $1.97         $1.94
BALANCE SHEET DATA:
Total assets........................  $6,075,683    $4,959,337    $4,923,550    $4,639,826    $4,476,406
Long-term obligations, net(3).......  $1,660,558    $1,713,649    $1,604,305    $1,444,355    $1,357,755
RATIO OF EARNINGS TO FIXED
  CHARGES...........................        3.19          2.17          2.77          3.21          3.17
</TABLE>

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

(1) The 1998 financial results reflect the recording of $54 million of pre-tax
    merger charges.

(2) Represents data for WPL Holdings, Inc. prior to the three-way merger
    involving WPL Holdings, Inc., IES Industries Inc. and Interstate Power
    Company in April 1998.

(3) Long-term obligations, net include long-term debt, current maturities,
    variable rate demand bonds, current and long-term capital lease obligations
    and mandatory redeemable preferred stock.

                                       12
<PAGE>   14

                      WHERE YOU CAN FIND MORE INFORMATION

     Alliant Energy Corporation, our parent corporation and the guarantor of the
senior notes, files annual, quarterly and current reports, proxy statements and
other information with the SEC. You may read and copy any document which Alliant
Energy Corporation files at the SEC's public reference rooms at 450 Fifth
Street, N.W., Washington D.C., and at regional SEC offices in Chicago, Illinois
and New York, New York. You can call the SEC at 1-800-SEC-0330 for further
information on the operation of the public reference rooms. You can also find
Alliant Energy Corporation's public filings with the SEC on the internet at a
website maintained by the SEC located at http://www.sec.gov.

     We are "incorporating by reference" specified documents that Alliant Energy
Corporation files with the SEC, which contain important business and financial
information not included in or delivered with this prospectus. "Incorporating by
reference" means:

     -  incorporated documents are considered part of this prospectus;

     -  we are disclosing important information to you by referring you to those
        documents; and

     -  information Alliant Energy Corporation files with the SEC will
        automatically update and supersede information contained in this
        offering memorandum.

     We incorporate by reference the documents we list below and any future
filings Alliant Energy Corporation makes with the SEC under Sections 13(a),
13(c), 14 or 15(d) of the Securities Exchange Act of 1934 after the date of this
prospectus and before the end of the exchange offer:


     -  Alliant Energy Corporation's Annual Report on Form 10-K for the year
        ended December 31, 1999; and



     -  Alliant Energy Corporation's Current Report on Form 8-K dated January
        25, 2000, as amended by Alliant Energy Corporation's Current Report on
        Form 8-K/A dated January 25, 2000, Alliant Energy Corporation's Current
        Report on Form 8-K dated January 26, 2000, Alliant Energy Corporation's
        Current Reports on Form 8-K dated February 1, 2000, and Alliant Energy
        Corporation's Current Report on Form 8-K dated April 7, 2000.


     YOU MAY REQUEST A COPY OF ANY OF THESE FILINGS (INCLUDING EXHIBITS), AT NO
COST, BY WRITING TO EDWARD M. GLEASON, VICE PRESIDENT-TREASURER AND CORPORATE
SECRETARY, ALLIANT ENERGY CORPORATION, 222 WEST WASHINGTON AVENUE, MADISON,
WISCONSIN 53703, OR BY CALLING MR. GLEASON AT (608) 252-3311. TO OBTAIN TIMELY
DELIVERY OF ANY OF THIS INFORMATION, YOU MUST MAKE YOUR REQUEST AT LEAST FIVE
BUSINESS DAYS PRIOR TO THE EXPIRATION OF THE EXCHANGE OFFER. THE DATE BY WHICH
YOU MUST MAKE YOUR REQUEST IS           , 2000.

     You should rely only on the information contained or incorporated by
reference in this document or to which we have referred you. We have not
authorized any other person to provide you with different information. This
prospectus may only be used where it is legal to sell these securities. You
should assume that the information contained or incorporated by reference in
this document is accurate as of the date on the front cover of the prospectus
only. Our and Alliant Energy Corporation's business, financial condition,
results of operations and prospects may have changed since that date.

                                       13
<PAGE>   15

                           FORWARD-LOOKING STATEMENTS

     This prospectus (including the information we incorporate by reference)
contains forward-looking statements that are not of historical fact and are
statements intended to qualify for the safe harbors from liability established
by the Private Securities Litigation Reform Act of 1995. From time to time, we
or Alliant Energy Corporation may make other forward-looking statements within
the meaning of the federal securities laws that involve judgments, assumptions
and other uncertainties beyond our control. These forward-looking statements may
include, among others, statements concerning revenue and cost trends, cost
recovery, cost reduction strategies and anticipated outcomes, pricing
strategies, changes in the utility industry, planned capital expenditures,
financing needs and availability, statements of expectations, beliefs, future
plans and strategies, anticipated events or trends and similar comments
concerning matters that are not historical facts. You are cautioned that these
statements are not a guarantee of future performance and that these
forward-looking statements are subject to risks and uncertainties that could
cause actual results to differ materially from those expressed in, or implied
by, these statements. Some, but not all, of the risks and uncertainties include:

     -  weather effects on sales and revenues,

     -  competitive factors,

     -  general economic conditions in the relevant service territory,

     -  federal and state regulatory or government actions, including issues
        associated with the deregulation of the utility industry,

     -  unanticipated construction and acquisition expenditures,

     -  issues related to stranded costs and their recovery,

     -  the operations of Alliant Energy Corporation's nuclear facilities,

     -  unanticipated costs associated with environmental remediation efforts
        being undertaken by Alliant Energy Corporation,

     -  unanticipated issues relating to establishing a transmission company,

     -  material changes in the value of our investment in McLeodUSA
        Incorporated,

     -  technological developments,

     -  employee workforce factors, including changes in key executives,
        collective bargaining agreements or work stoppages,

     -  political, legal and economic conditions in foreign countries Alliant
        Energy Corporation has investments in, and

     -  changes in the rate of inflation.

                                       14
<PAGE>   16

                                USE OF PROCEEDS

     This exchange offer is intended to satisfy our obligations under the
registration rights agreement entered into in connection with the issuance of
the existing senior notes. We will not receive any cash proceeds from the
issuance of the new senior notes. We added the net proceeds of approximately
$247 million from the sale of the existing senior notes to our general funds. We
then used these general funds to repay commercial paper we issued in connection
with the development and acquisition of our non-regulated businesses as it
became due.

                                 CAPITALIZATION

     The following table sets forth the consolidated capitalization of Alliant
Energy Corporation, including us, as of December 31, 1999, and as adjusted to
give effect to the issuance of $402.5 million of exchangeable senior notes due
2030. See "Description of Outstanding Indebtedness."

<TABLE>
<CAPTION>
                                                                    DECEMBER 31, 1999
                                                         ---------------------------------------
                                                           ACTUAL      ADJUSTMENTS     ADJUSTED
                                                         ----------    -----------    ----------
                                                                     (IN THOUSANDS)
<S>                                                      <C>           <C>            <C>
Common stock.........................................    $      790           --      $      790
Additional paid-in capital...........................       942,408           --         942,408
Retained earnings....................................       577,464           --         577,464
Accumulated other comprehensive income...............       634,903           --         634,903
                                                         ----------     --------      ----------
  Total common equity................................     2,155,565           --       2,155,565
                                                         ----------     --------      ----------
Cumulative preferred stock of subsidiaries...........       113,638           --         113,638
Long-term debt (excluding current portion):
                                                         ----------     --------      ----------
Exchangeable senior notes............................            --     $402,500         402,500
Other long-term debt.................................     1,486,765           --       1,486,765
                                                         ----------     --------      ----------
  Total long-term debt...............................     1,486,765      402,500       1,889,265
                                                         ----------     --------      ----------
       Total capitalization..........................    $3,755,968     $402,500      $4,158,468
                                                         ==========     ========      ==========
</TABLE>

                                       15
<PAGE>   17

                               THE EXCHANGE OFFER

PURPOSE AND EFFECT; REGISTRATION RIGHTS

     We sold the existing senior notes on November 9, 1999 in transactions
exempt from the registration requirements of the Securities Act. Therefore, the
existing senior notes are subject to significant restrictions on resale. In
connection with the issuance of the existing senior notes, we entered into a
registration rights agreement, which required that we and Alliant Energy
Corporation:

     -  file with the SEC a registration statement under the Securities Act
        relating to the exchange offer and the issuance and delivery of new
        senior notes in exchange for the existing senior notes;

     -  use our reasonable best efforts to cause the SEC to declare the exchange
        offer registration statement effective under the Securities Act; and

     -  use our reasonable best efforts to consummate the exchange offer not
        later than 45 days following the effective date of the exchange offer
        registration statement.

     If you participate in the exchange offer, you will, with limited
exceptions, receive new senior notes that are freely tradeable and not subject
to restrictions on transfer. You should read this prospectus under the heading
"-- Resales of New Senior Notes" for more information relating to your ability
to transfer new senior notes.

     If you are eligible to participate in the exchange offer and do not tender
your existing senior notes, you will continue to hold the untendered existing
senior notes, which will continue to be subject to restrictions on transfer
under the Securities Act.

     The exchange offer is intended to satisfy our exchange offer obligations
under the registration rights agreement. The above summary of the registration
rights agreement is not complete and is subject to, and qualified by reference
to, all the provisions of the registration rights agreement. A copy of the
registration rights agreement has been filed as an exhibit to the registration
statement that includes this prospectus.

TERMS OF THE EXCHANGE OFFER

     We are offering to exchange $250,000,000 in aggregate principal amount of
our 7 3/8% Senior Notes due 2009 that have been registered under the Securities
Act for a like principal amount of our outstanding unregistered 7 3/8% Senior
Notes due 2009.

     Upon the terms and subject to the conditions set forth in this prospectus
and in the accompanying letter of transmittal, we will accept all existing
senior notes validly tendered and not withdrawn before 5:00 p.m., New York City
time, on the expiration date of the exchange offer. We will issue $1,000
principal amount of new senior notes in exchange for each $1,000 principal
amount of outstanding existing senior notes we accept in the exchange offer. You
may tender some or all of your existing senior notes under the exchange offer.
However, the existing senior notes are issuable in authorized denominations of
$1,000 and integral multiples thereof. Accordingly, existing senior notes may be
tendered only in denominations of $1,000 and integral multiples thereof. The
exchange offer is not conditioned upon any minimum amount of original notes
being tendered.

     The form and terms of the new senior notes will be the same as the form and
terms of the existing senior notes, except that:

     - the new senior notes will be registered with the SEC and thus will not be
       subject to the restrictions on transfer or bear legends restricting their
       transfer;

     - all of the new senior notes will be represented by global notes in
       book-entry form unless exchanged for notes in definitive certificated
       form under the limited circumstances described under "Description of the
       New Senior Notes -- Book-Entry Procedures and Form;" and

     - the new senior notes will not provide for the payment of additional
       interest under circumstances relating to the timing of the exchange
       offer.
                                       16
<PAGE>   18

     The new senior notes will evidence the same debt as the existing senior
notes and will be issued under, and be entitled to the benefits of, the
indenture, as supplemented, governing the existing senior notes.

     The new senior notes will accrue interest from the most recent date to
which interest has been paid on the existing senior notes or, if no interest has
been paid, from the date of issuance of the existing senior notes. Accordingly,
registered holders of new senior notes on the record date for the first interest
payment date following the completion of the exchange offer will receive
interest accrued from the most recent date to which interest has been paid on
the existing senior notes or, if no interest has been paid, from the date of
issuance of the existing senior notes. However, if that record date occurs prior
to completion of the exchange offer, then the interest payable on the first
interest payment date following the completion of the exchange offer will be
paid to the registered holders of the existing senior notes on that record date.

     In connection with the exchange offer, you do not have any appraisal or
dissenters' rights under the Wisconsin Business Corporation Law or the
indenture, as supplemented. We intend to conduct the exchange offer in
accordance with the registration rights agreement and the applicable
requirements of the Securities Exchange Act of 1934 and the rules and
regulations of the SEC.

     We will be deemed to have accepted validly tendered existing senior notes
when we have given oral or written notice of our acceptance to the exchange
agent. The exchange agent will act as agent for the tendering holders for the
purpose of receiving the new senior notes from us.

     If we do not accept any tendered existing senior notes because of an
invalid tender or for any other reason, then we will return certificates for any
unaccepted existing senior notes without expense to the tendering holder as
promptly as practicable after the expiration date.

EXPIRATION DATE; AMENDMENTS

     The exchange offer will expire at 5:00 p.m., New York City time, on
          , 2000, unless we, in our sole discretion, extend the exchange offer.

     If we determine to extend the exchange offer, then we will notify the
exchange agent of any extension by oral or written notice and give each
registered holder notice of the extension by means of a press release or other
public announcement before 9:00 a.m., New York City time, on the next business
day after the previously scheduled expiration date.

     We reserve the right, in our sole discretion, to delay accepting any
existing senior notes, to extend the exchange offer or to amend or terminate the
exchange offer if any of the conditions described below under "-- Conditions"
have not been satisfied or waived by giving oral or written notice to the
exchange agent of the delay, extension, amendment or termination. Further, we
reserve the right, in our sole discretion, to amend the terms of the exchange
offer in any manner. We will notify you as promptly as practicable of any
extension, amendment or termination. We will also file a post-effective
amendment to the registration statement of which this prospectus is a part with
respect to any fundamental change in the exchange offer.

PROCEDURES FOR TENDERING EXISTING SENIOR NOTES

     Any tender of existing senior notes that is not withdrawn prior to the
expiration date will constitute a binding agreement between the tendering holder
and us upon the terms and subject to the conditions set forth in this prospectus
and in the accompanying letter of transmittal. A holder who wishes to tender
existing senior notes in the exchange offer must do either of the following:

     -  properly complete, sign and date the letter of transmittal, including
        all other documents required by the letter of transmittal; have the
        signature on the letter of transmittal guaranteed if the letter of
        transmittal so requires; and deliver that letter of transmittal and
        other required documents to the exchange agent at the address listed
        below under "-- Exchange Agent" on or before the expiration date; or

                                       17
<PAGE>   19

     -  if the existing senior notes are tendered under the book-entry transfer
        procedures described below, transmit to the exchange agent on or before
        the expiration date an agent's message.

     In addition, one of the following must occur:

     -  the exchange agent must receive certificates representing your existing
        senior notes, along with the letter of transmittal, on or before the
        expiration date; or

     -  the exchange agent must receive a timely confirmation of book-entry
        transfer of the existing senior notes into the exchange agent's account
        at DTC under the procedure for book-entry transfers described below,
        along with the letter of transmittal or a properly transmitted agent's
        message, on or before the expiration date; or

     -  the holder must comply with the guaranteed delivery procedures described
        below.

     The term "agent's message" means a message, transmitted by a book-entry
transfer facility to and received by the exchange agent and forming a part of
the book-entry confirmation, which states that the book-entry transfer facility
has received an express acknowledgement from the tendering participant stating
that the participant has received and agrees to be bound by the letter of
transmittal and that we may enforce the letter of transmittal against the
participant.

     The method of delivery of existing senior notes, the letter of transmittal
and all other required documents to the exchange agent is at your election and
risk. Rather than mail these items, we recommend that you use an overnight or
hand delivery service. In all cases, you should allow sufficient time to assure
timely delivery to the exchange agent before the expiration date. Do not send
letters of transmittal or existing senior notes to us.

     Generally, an eligible institution must guarantee signatures on a letter of
transmittal or a notice of withdrawal unless the existing senior notes are
tendered:

     -  by a registered holder of the existing senior notes who has not
        completed the box entitled "Special Issuance Instructions" or "Special
        Delivery Instructions" on the letter of transmittal; or

     -  for the account of an eligible institution.

     If signatures on a letter of transmittal or a notice of withdrawal are
required to be guaranteed, the guarantee must be by a firm which is:

     -  a member of a registered national securities exchange;

     -  a member of the National Association of Securities Dealers, Inc.;

     -  a commercial bank or trust company having an office or correspondent in
        the United States; or

     -  another "eligible institution" within the meaning of Rule 17Ad-15 under
        the Securities Exchange Act.

     If the letter of transmittal is signed by a person other than the
registered holder of any outstanding existing senior notes, the original notes
must be endorsed or accompanied by appropriate powers of attorney. The power of
attorney must be signed by the registered holder exactly as the registered
holder(s) name(s) appear(s) on the existing senior notes and an eligible
institution must guarantee the signature on the power of attorney.

     If the letter of transmittal, or any existing senior notes or powers of
attorney are signed by trustees, executors, administrators, guardians,
attorneys-in-fact, officers of corporations or others acting in a fiduciary or
representative capacity, these persons should so indicate when signing. Unless
waived by us, they should also submit evidence satisfactory to us of their
authority to so act.

     If you wish to tender existing senior notes that are registered in the name
of a broker, dealer, commercial bank, trust company or other nominee, you should
promptly instruct the registered holder to tender on your behalf. If you wish to
tender on your behalf, you must, before completing the procedures

                                       18
<PAGE>   20

for tendering existing senior notes, either register ownership of the existing
senior notes in your name or obtain a properly completed bond power from the
registered holder. The transfer of registered ownership may take considerable
time.

     We will determine in our sole discretion all questions as to the validity,
form, eligibility, including time of receipt, and acceptance of existing senior
notes tendered for exchange. Our determination will be final and binding on all
parties. We reserve the absolute right to reject any and all tenders of existing
senior notes not properly tendered or existing senior notes our acceptance of
which might, in the judgment of our counsel, be unlawful. We also reserve the
absolute right to waive any defects, irregularities or conditions of tender as
to any particular existing senior notes. Our interpretation of the terms and
conditions of the exchange offer, including the instructions in the letter of
transmittal, will be final and binding on all parties. Unless waived, any
defects or irregularities in connection with tenders of existing senior notes
must be cured within the time period we determine. Neither we, the exchange
agent nor any other person will incur any liability for failure to give you
notification of defects or irregularities with respect to tenders of your
existing senior notes.

     By tendering, you will represent to us that:

     -  the new senior notes acquired in the exchange offer are being acquired
        in the ordinary course of business of the person receiving the new
        senior notes;

     -  neither you nor any other person receiving your new senior notes has any
        arrangement or understanding with any person to participate in the
        distribution of the new senior notes; and

     -  neither you nor any other person receiving your new senior notes is our
        "affiliate," as defined under Rule 405 of the Securities Act.

     If you or the person receiving your new senior notes is our "affiliate," as
defined under Rule 405 of the Securities Act, or is participating in the
exchange offer for the purpose of distributing the new senior notes, you or that
other person cannot rely on the applicable interpretations of the staff of the
SEC, cannot tender your existing senior notes in the exchange offer and must
comply with the registration and prospectus delivery requirements of the
Securities Act in any resale transaction.

     If you are a broker-dealer and you will receive new senior notes for your
own account in exchange for the existing senior notes, where these existing
senior notes were acquired as a result of market-making activities or other
trading activities, then you must acknowledge that you will deliver a prospectus
in connection with any resale of the new senior notes.

ACCEPTANCE OF EXISTING SENIOR NOTES FOR EXCHANGE; DELIVERY OF NEW SENIOR NOTES

     Upon satisfaction of all conditions to the exchange offer, we will accept,
promptly after the expiration date, all existing senior notes properly tendered
and will issue the new senior notes promptly after acceptance of the existing
senior notes.

     For purposes of the exchange offer, we will be deemed to have accepted
properly tendered existing senior notes for exchange when we have given oral or
written notice of that acceptance to the exchange agent. For each existing
senior note accepted for exchange, you will receive a new senior note having a
principal amount equal to that of the surrendered existing senior note.

     In all cases, we will issue new senior notes for existing senior notes that
we have accepted for exchange under the exchange offer only after the exchange
agent timely receives:

     - certificates for your existing senior notes or a timely confirmation of
       book-entry transfer of your existing senior notes into the exchange
       agent's account at DTC; and

     - a properly completed and duly executed letter of transmittal and all
       other required documents or a properly transmitted agent's message.

                                       19
<PAGE>   21

     If we do not accept any tendered existing senior notes for any reason set
forth in the terms of the exchange offer or if you submit existing senior notes
for a greater principal amount than you desire to exchange, we will return the
unaccepted or non-exchanged existing senior notes without expense to you. In the
case of existing senior notes tendered by book-entry transfer into the exchange
agent's account at DTC under the book-entry procedures described below, we will
credit the non-exchanged existing senior notes to your account maintained with
DTC.

BOOK-ENTRY TRANSFER

     We understand that the exchange agent will make a request within two
business days after the date of this prospectus to establish accounts for the
existing senior notes at DTC for the purpose of facilitating the exchange offer,
and any financial institution that is a participant in DTC's system may make
book-entry delivery of existing senior notes by causing DTC to transfer the
existing senior notes into the exchange agent's account at DTC in accordance
with DTC's procedures for transfer. Although delivery of existing senior notes
may be effected through book-entry transfer at DTC, the exchange agent must
receive a properly completed and duly executed letter of transmittal with any
required signature guarantees, or an agent's message instead of a letter of
transmittal, and all other required documents at its address listed below under
"-- Exchange Agent" on or before the expiration date, or if you comply with the
guaranteed delivery procedures described below, within the time period provided
under those procedures.

GUARANTEED DELIVERY PROCEDURES

     If you wish to tender your existing senior notes and your existing senior
notes are not immediately available, or you cannot deliver your existing senior
notes, the letter of transmittal or any other required documents or comply with
DTC's procedures for transfer before the expiration date, then you may
participate in the exchange offer if:

     -  the tender is made through an eligible institution;

     -  before the expiration date, the exchange agent receives from the
        eligible institution a properly completed and duly executed notice of
        guaranteed delivery, substantially in the form provided by us, by
        facsimile transmission, mail or hand delivery, containing:

       - the name and address of the holder and the principal amount of existing
         senior notes tendered,

       - a statement that the tender is being made thereby, and

       - a guarantee that within three New York Stock Exchange trading days
         after the expiration date, the certificates representing the existing
         senior notes in proper form for transfer or a book-entry confirmation
         and any other documents required by the letter of transmittal will be
         deposited by the eligible institution with the exchange agent; and

     -  the exchange agent receives the properly completed and executed letter
        of transmittal as well as certificates representing all tendered
        existing senior notes in proper form for transfer, or a book-entry
        confirmation, and all other documents required by the letter of
        transmittal within three New York Stock Exchange trading days after the
        expiration date.

WITHDRAWAL RIGHTS

     You may withdraw your tender of existing senior notes at any time before
the exchange offer expires.

     For a withdrawal to be effective, the exchange agent must receive a written
notice of withdrawal at its address listed below under "-- Exchange Agent." The
notice of withdrawal must:

     -  specify the name of the person who tendered the existing senior notes to
        be withdrawn;

     -  identify the existing senior notes to be withdrawn, including the
        principal amount, or, in the case of existing senior notes tendered by
        book-entry transfer, the name and number of the DTC account to be
        credited, and otherwise comply with the procedures of DTC; and
                                       20
<PAGE>   22

     -  if certificates for existing senior notes have been transmitted, specify
        the name in which those existing senior notes are registered if
        different from that of the withdrawing holder.

     If you have delivered or otherwise identified to the exchange agent the
certificates for existing senior notes, then, before the release of these
certificates, you must also submit the serial numbers of the particular
certificates to be withdrawn and a signed notice of withdrawal with the
signatures guaranteed by an eligible institution, unless the holder is an
eligible institution.

     We will determine in our sole discretion all questions as to the validity,
form and eligibility, including time of receipt, of notices of withdrawal. Our
determination will be final and binding on all parties. Any existing senior
notes so withdrawn will be deemed not to have been validly tendered for purposes
of the exchange offer. We will return any existing senior notes that have been
tendered but that are not exchanged for any reason to the holder, without cost,
as soon as practicable after withdrawal, rejection of tender or termination of
the exchange offer. In the case of existing senior notes tendered by book-entry
transfer into the exchange agent's account at DTC, the existing senior notes
will be credited to an account maintained with DTC for the existing senior
notes. You may retender properly withdrawn existing senior notes by following
one of the procedures described under "-- Procedures for Tendering Existing
Senior Notes" at any time on or before the expiration date.

CONDITIONS

     Notwithstanding any other term of the exchange offer, we will not be
required to accept for exchange, or to exchange new senior notes for, any
existing senior notes if:

     -  the exchange offer, or the making of any exchange by a holder of
        existing senior notes, would violate any applicable law or applicable
        interpretation by the staff of the SEC; or

     -  any action or proceeding is instituted or threatened in any court or by
        or before any governmental agency with respect to the exchange offer
        which, in our judgment, would reasonably be expected to impair our
        ability to proceed with the exchange offer.

     The conditions listed above are for our sole benefit and we may assert them
regardless of the circumstances giving rise to any condition. Subject to
applicable law, we may waive these conditions in our discretion in whole or in
part at any time and from time to time. If we waive these conditions, then we
intend to continue the exchange offer for at least five business days after the
waiver. If we fail at any time to exercise any of the above rights, the failure
will not be deemed a waiver of those rights, and those rights will be deemed
ongoing rights which may be asserted at any time and from time to time.

EXCHANGE AGENT

     Firstar Bank, N.A. is the exchange agent for the exchange offer. You should
direct any questions and requests for assistance and requests for additional
copies of this prospectus, the letter of transmittal or the notice of guaranteed
delivery to the exchange agent addressed as follows:

     By Hand, Overnight Mail, Courier, or Registered or Certified Mail:

        Firstar Bank, N.A.
        1555 North RiverCenter Drive
        Suite 301
        Milwaukee, Wisconsin 53212
        Attention: Peter M. Brennan

                                       21
<PAGE>   23

     By Facsimile:

        (414) 905-5003
        Attention: Peter M. Brennan

     Delivery of the letter of transmittal to an address other than as listed
above or transmission via facsimile other than as listed above will not
constitute a valid delivery of the letter of transmittal.

FEES AND EXPENSES

     We will pay the expenses of the exchange offer. We will not make any
payments to brokers, dealers or others soliciting acceptances of the exchange
offer. We are making the principal solicitation by mail; however, our officers
and employees may make additional solicitations by facsimile transmission,
e-mail, telephone or in person. You will not be charged a service fee for the
exchange of your senior notes, but we may require you to pay any transfer or
similar government taxes in certain circumstances.

TRANSFER TAXES

     You will not be obligated to pay any transfer taxes, unless you instruct us
to register new senior notes in the name of, or request that existing senior
notes not tendered or not accepted in the exchange offer be returned to, a
person other than the registered tendering holder.

ACCOUNTING TREATMENT

     We will record the new senior notes at the same carrying values as the
existing senior notes, which is the aggregate principal amount of the existing
senior notes, as reflected in our accounting records on the date of exchange.
Accordingly, we will not recognize any gain or loss on the exchange of senior
notes. We will amortize the expenses of the offer over the term of the new
senior notes.

CONSEQUENCES OF FAILURE TO EXCHANGE EXISTING SENIOR NOTES

     If you are eligible to participate in the exchange offer but do not tender
your existing senior notes, you will not have any further registration rights.
Your existing senior notes will continue to be subject to restrictions on
transfer. Accordingly, you may resell the existing senior notes that are not
exchanged only:

     - to us;

     - so long as the existing senior notes are eligible for resale under Rule
       144A under the Securities Act, to a person whom you reasonably believe is
       a "qualified institutional buyer" within the meaning of Rule 144A
       purchasing for its own account or for the account of a qualified
       institutional buyer in a transaction meeting the requirements of Rule
       144A;

     - in accordance with Rule 144 under the Securities Act or another exemption
       from the registration requirements of the Securities Act;

     - to an institutional accredited investor as defined in Rule 501(a)(1),
       (2), (3) or (7) under the Securities Act that is acquiring the existing
       senior notes for its own account or for the account of an institutional
       accredited investor for investment purposes and not with a view to, or
       for offer or sale in connection with, any distribution in violation of
       the Securities Act; or

     - under any effective registration statement under the Securities Act;

in each case in accordance with all other applicable securities laws. We do not
intend to register the existing senior notes under the Securities Act.

RESALES OF NEW SENIOR NOTES

     We are making the exchange offer in reliance on the position of the staff
of the SEC as set forth in interpretive letters addressed to third parties in
other transactions. However, we have not sought our own

                                       22
<PAGE>   24

interpretive letter, and we cannot provide any assurance that the staff of the
SEC would make a similar determination with respect to the exchange offer as it
has in the interpretive letters addressed to third parties. Based on these
interpretations by the staff of the SEC, and except as provided below, we
believe that new senior notes may be offered for resale, resold and otherwise
transferred by a holder that participates in the exchange offer and is not a
broker-dealer without further compliance with the registration and prospectus
delivery provisions of the Securities Act. To receive new senior notes that are
freely tradeable, a holder must acquire the new senior notes in the ordinary
course of its business and may not participate, or have any arrangement or
understanding with any person to participate, in the "distribution" within the
meaning of the Securities Act of the existing senior notes or the new senior
notes. Holders wishing to participate in the exchange offer must make the
representations described in " -- Procedures for Tendering Existing Senior
Notes" above.

     Any holder of existing senior notes:

     - who is our "affiliate," as defined in Rule 405 under the Securities Act;

     - who did not acquire the new senior notes in the ordinary course of its
       business;

     - who intends to participate, or has an arrangement or understanding with
       any person to participate, in a "distribution" within the meaning of the
       Securities Act of the existing senior notes or the new senior notes; or

     - who purchased the existing senior notes directly from us to resell
       pursuant to Rule 144A or any other available exemption under the
       Securities Act,

will be subject to separate restrictions. Each holder in any of the above
categories:

     - will not be ably to rely on the interpretations of the staff of the SEC
       in the above-mentioned interpretative letters;

     - will not be permitted or entitled to tender existing senior notes in the
       exchange offer; and

     - must comply with the registration and prospectus delivery requirements of
       the Securities Act, including being named as a selling security holder,
       in connection with any sale or other transfer of existing senior notes
       unless such sale is made pursuant to an exemption from these
       requirements.

     In addition, if you are a broker-dealer holding existing senior notes
acquired for your own account, then you may be deemed a statutory "underwriter"
within the meaning of the Securities Act in connection with any resales of your
new senior notes. Each broker-dealer that receives new senior notes for its own
account pursuant to the exchange offer must acknowledge that it acquired the
existing senior notes for its own account as a result of market-making
activities or other trading activities and must agree that it will deliver a
prospectus meeting the requirements of the Securities Act in connection with any
resale of those new senior notes. The letter of transmittal states that by
making the above acknowledgement and by delivering a prospectus, a broker-dealer
will not be deemed to admit that it is an "underwriter" within the meaning of
the Securities Act.

     Based on the position taken by the staff of the SEC in the interpretative
letters referred to above, we believe that broker-dealers who acquired existing
senior notes for their own accounts, as a result of market-making or other
trading activities may fulfill their prospectus delivery requirements with
respect to the new senior notes received upon the exchange of existing senior
notes, other than existing senior notes that represent an unsold allotment from
the original sale of the existing senior notes, with a prospectus meeting the
requirements of the Securities Act, which may be the prospectus prepared for an
exchange offer so long as it contains a description of the plan of distribution
with respect to the sale of such new senior notes. Accordingly, this prospectus,
as it may be amended or supplemented, may be used by a participating
broker-dealer in connection with resales of new senior notes received in
exchange for existing senior notes where such existing senior notes were
acquired by that participating broker-dealer for its own account as a result of
market-making or other trading activities. See "Plan of Distribution." However,
a participating broker-dealer who intends to use this prospectus in connection
with the resale of new senior

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<PAGE>   25

notes received in exchange for existing senior notes pursuant to the exchange
offer must notify us, or cause us to be notified, on or before the expiration
date of the exchange offer, that it is a participating broker-dealer. Such
notice may be given in the space provided for that purpose in the letter of
transmittal or may be delivered to the exchange agent at the address set forth
above under " --  Exchange Agent." Any participating broker-dealer who is an
"affiliate" of ours may not rely on such interpretive letters and must comply
with the registration and prospectus delivery requirements of the Securities Act
in connection with any resale transaction.

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<PAGE>   26

                                    BUSINESS

OVERVIEW

     We are a wholly-owned subsidiary of Alliant Energy Corporation, which is a
registered public utility holding company. We manage a portfolio of companies
involved in non-regulated businesses. Our primary subsidiaries include Alliant
Energy Investments, Inc.; Alliant Energy International, Inc.; and Alliant Energy
Industrial Services, Inc. Alliant Energy Corporation also has a 50% ownership
interest in a joint venture with Cargill Incorporated, named Cargill-Alliant
LLC.

     We were incorporated in Wisconsin in 1988 as Heartland Development
Corporation, a subsidiary of WPL Holdings, Inc. As part of a three-way merger
involving our parent in April 1998, we merged with IES Diversified Inc., the
holding company for the non-regulated businesses of the former IES Industries
Inc., to form Alliant Energy Resources, Inc.

STRATEGY

     As competitive forces shape the energy-services industry, energy providers
are being challenged to increase growth and profits. Because we expect
consumption of electricity and natural gas to grow only modestly within Alliant
Energy Corporation's domestic utility service territory, we have entered several
energy-services markets that we expect will provide opportunities for new
sources of growth. We have established new distinct platforms to complement our
existing non-regulated investments, which are designed to meet customer needs.
These platforms and existing investments include:

     -  Investments:  Our existing investments include an oil and gas production
        company, a short-line railroad, a barge company, an affordable housing
        company, various real estate joint ventures and an equity stake in an
        independent telecommunications provider.

     -  International:  We are a partner in developing, or are seeking to
        develop, energy generation and infrastructure in New Zealand, Australia,
        China, Mexico and Brazil, markets which we have selected because of
        their growth potential.

     -  Industrial Services:  We are a provider of energy and environmental
        services designed to maximize productivity for industrial and large
        commercial customers. This platform consists of four units: Energy
        Planning; Energy Management; Energy Applications, which provides
        facilities-based and commodities-based energy solutions; and RMT, Inc.,
        an environmental-management and engineering firm with offices throughout
        the United States and the United Kingdom. We believe these four
        components comprise an industrial services company with expertise that
        customers find valuable.

     -  Cargill-Alliant:  Alliant Energy Corporation has an energy-trading joint
        venture with Cargill Incorporated that combines the risk-management and
        commodity trading expertise of Cargill with Alliant Energy Corporation's
        low-cost electricity generation and transmission business experience.
        Cargill-Alliant LLC officially began operations in 1997 and has an
        initial term through October 2002. The term automatically renews for
        successive five-year periods unless either party notifies the other at
        least one year prior to the then expiring term, in which case the other
        party must decide whether to sell its interest in the joint venture to
        the nonrenewing party or acquire the nonrenewing party's interest.

     -  Mass Markets:  We are a provider of products and services designed to
        meet the comfort, security and productivity needs of residential and
        small commercial customers. We offer home appliance and furnace
        warranties and a variety of home energy, safety and security products
        through our "Power House" catalog. We market these products directly to
        customers, through the mail with our catalog and over the Internet. We
        expect to continue to pursue opportunities in these markets, which we
        believe have growth potential as industry deregulation allows more
        customers to choose their energy suppliers in an open market.

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<PAGE>   27

PRINCIPAL OPERATIONS

     We conduct our operations through our principal subsidiaries and
investments, which are engaged in the businesses described below:

     Investments:  Our subsidiaries and investments include Whiting Petroleum
Corporation, Alliant Energy Transportation, Inc. and Alliant Energy Investments,
Inc., which is a holding company whose primary subsidiaries include Heartland
Properties, Inc. and Capital Square Financial Corporation and which holds an
equity stake in McLeodUSA Incorporated. Alliant Energy Investments also has
direct and indirect equity interests in various real estate and economic
development ventures, primarily concentrated in Iowa.

     -  Whiting Petroleum is based in Denver, Colorado and was organized to
        purchase, develop and produce crude oil and natural gas. Whiting
        Petroleum's construction and acquisition expenditures were approximately
        $60 million in 1998 and $35 million in 1999.

     -  Alliant Energy Transportation is a holding company whose equity
        investments total $31 million as of December 31, 1999 and include the
        Cedar Rapids and Iowa City Railway Company, a short-line railway, which
        renders freight service between Cedar Rapids and Iowa City, Transfer
        Services, Inc. and Williams Bulk Transfer, Inc., which provide
        transloading and storage services, and a 75% equity investment in IEI
        Barge Services Inc., which provides barge terminal and hauling services
        on the Mississippi River.

     -  Heartland Properties, formed in 1988, is responsible for performing
        asset management and facilitating the development and financing of high
        quality, affordable housing in Wisconsin and the Midwest. Heartland
        Properties has a majority ownership interest in approximately 60
        properties.

     -  Capital Square was incorporated in 1992 to provide mortgage banking
        services to facilitate Heartland Properties' development and financing
        efforts in the affordable housing market.

     -  We also hold an equity interest of approximately 10.5% in McLeodUSA
        Incorporated. McLeodUSA is an independent telecommunications provider
        based in Cedar Rapids, Iowa. Our investment in McLeodUSA had a market
        value of approximately $1.1 billion as of December 31, 1999 (based on a
        closing price of $58.875 per share and compared to a cost basis of
        approximately $28 million). Alliant Energy Investments is a party to a
        stockholders' agreement that provides, subject to some exceptions, that
        it may not sell any equity securities of McLeodUSA until December 31,
        2001 without the consent of the Board of Directors of McLeodUSA.

     International:  Our international operations include Alliant Energy
International, Inc., a holding company whose primary investments include Alliant
International New Zealand Limited, Alliant Energy Australia Pty Ltd., Interstate
Energy Corporation Pte. Ltd., Grandelight Holdings Ltd., Alliant Energy de
Mexico L.L.C. and Alliant Energy Brazil, Inc.

     -  Alliant International New Zealand has made equity investments in several
        New Zealand utility entities since 1995, which totaled $108 million as
        of December 31, 1999. As a result of electricity reforms since 1995,
        several utility companies exited generation and retail businesses. As
        part of its strategy to enter the generation and retail markets, Alliant
        International New Zealand sold all of its interest in Central Power
        Limited and a portion of its interest in Powerco Limited, each of which
        were electricity distribution companies. Alliant International New
        Zealand has a 10% interest in Infrastructure and Utilities NZ Ltd., a
        holding company for infrastructure and utility businesses in New Zealand
        and a 17% interest in TrustPower Ltd., an electricity generation and
        retail company. Alliant International New Zealand and Infrastructure and
        Utilities NZ Ltd. hold a collective interest in TrustPower of
        approximately 42%.

     -  In October 1999, Alliant Energy Australia acquired a 10% equity interest
        in Infratil Australia Limited, a holding company for infrastructure and
        utility businesses in Australia. Alliant Energy Australia also closed on
        the acquisition of a 22% equity interest in Southern Hydro Partnership,
        a hydro-electricity generation business, in February 2000.

                                       26
<PAGE>   28

     -  As of December 31, 1999, Alliant Energy International has invested $62
        million in investments in China, which consist of an equity investment
        of $27 million in two individual cogeneration facilities in China and an
        equity investment of $35 million in Peak Pacific Investment Company PTE
        Ltd. Peak Pacific was formed to develop investment opportunities in
        generation infrastructure projects in China. In addition, we have
        commitments of an additional $11 million to invest in China as of
        December 31, 1999.

     -  Alliant Energy de Mexico owns two subsidiaries incorporated in Mexico
        that have entered into agreements to operate the electrical
        distributions facilities serving a resort community known as Laguna del
        Mar, located in Puerto Penasco, Sonora, Mexico. As of December 31, 1999,
        Alliant Energy International's investment consisted of $10 million in
        secured debentures of Laguna del Mar.

     -  Alliant Energy Brazil was formed for the purpose of making investments
        in Brazil. On January 25, 2000, our subsidiary, Alliant Energy Holdings
        do Brazil Ltda., acquired, for approximately $347 million, an equity
        stake in Brazilian utility operations serving an aggregate of
        approximately 820,000 customers. Alliant Energy Brazil will continue to
        examine similar opportunities to invest in electricity generation and
        distribution entities that have arisen as a result of the Brazilian
        government's privatization of the electricity sector.

     Industrial Services:  Our industrial services include Alliant Energy
Industrial Services, Inc., a holding company whose primary wholly-owned
subsidiaries include Industrial Energy Applications, Inc., Heartland Energy
Group, Inc. and RMT, Inc.

     -  Industrial Energy Applications and Heartland Energy Group offer to their
        customers commodities-based energy services, such as supplying natural
        gas and electricity, and facilities-based energy services, including
        standby generation, cogeneration, steam production and propane air
        systems. They also provide energy consulting services for customers and
        own two oil and natural gas gathering systems in Texas.

     -  RMT is a Madison, Wisconsin-based environmental and engineering
        consulting company that serves clients nationwide in a variety of
        industrial market segments. The most significant of these markets are
        chemical companies, pulp and paper processors, oil and gas providers,
        foundries and other manufacturers. RMT specializes in consulting on
        solid and hazardous waste management, ground water quality protection,
        industrial design and hygiene engineering, and air and water pollution
        control.

                                       27
<PAGE>   29

                    DESCRIPTION OF OUTSTANDING INDEBTEDNESS

     The following is information concerning our indebtedness other than the
existing senior notes.

     We are a party to a revolving 3-Year Credit Agreement with various banking
institutions. This agreement extends through October 2000, with one-year
extensions available upon agreement by the parties. We also use unused borrowing
availability under this agreement to support our commercial paper program. A
combined maximum of $450 million of borrowings under this agreement and the
commercial paper program may be outstanding at any time. Interest rates and
maturities are set at the time of borrowing. The rates are based upon quoted
market prices and the maturities are less than one year. At December 31, 1999,
we had no direct borrowings under this facility and $139 million of commercial
paper outstanding and backed by this facility, with interest rates ranging from
5.90% to 6.32% and maturities ranging from 11 to 53 days. We intend to continue
issuing commercial paper backed by this facility. At December 31, 1999, we had
$311 million of credit capacity available under this facility. No conditions
existed at December 31, 1999 that would prevent the issuance of commercial paper
or direct borrowings under the 3-Year Credit Agreement. The new senior notes
will rank equally with indebtedness under the 3-Year Credit Agreement.

     We are also a party to a revolving 364-Day Credit Agreement with various
banking institutions. This agreement extends through October 16, 2000, with
364-day extensions available upon agreement by the parties. We also use the
unborrowed portion of this agreement to support our commercial paper program. A
combined maximum of $150 million of borrowings under this agreement and
commercial paper backed by this facility may be outstanding at any one time.
Interest rates and maturities are set at the time of borrowing. The rates are
based upon quoted market prices and the maturities are less than one year. At
December 31, 1999, we had no borrowings under this facility and no commercial
paper backed by this facility outstanding and we had $150 million of credit
capacity available under this facility. No conditions existed at December 31,
1999 that would prevent the issuance of commercial paper or direct borrowings
under the 364-Day Credit Agreement. The new senior notes will rank equally with
indebtedness under the 364-Day Credit Agreement.

     On February 1, 2000, we completed a private placement of 5,940,960
exchangeable senior notes in accordance with Rule 144A under the Securities Act.
The exchangeable senior notes were issued in the initial aggregate principal
amount of $402.5 million and will be due in 2030. The exchangeable senior notes
have an interest rate of 7.25% through February 15, 2003 and 2.5% after that
date. The exchangeable senior notes are exchangeable for cash based upon the
value of McLeodUSA Incorporated Class A Common Stock. Alliant Energy Corporation
has agreed to fully and unconditionally guarantee the payment of principal and
interest on the exchangeable senior notes. The exchangeable senior notes were
issued as a series of debt under the same indenture that the existing senior
notes were, and the new senior notes will be, issued. The new senior notes will
rank equally with the exchangeable senior notes.

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<PAGE>   30

                      DESCRIPTION OF THE NEW SENIOR NOTES

     The existing senior notes were, and the new senior notes will be, issued
under and governed by an Indenture, as supplemented and amended by the First
Supplemental Indenture, each dated as of November 4, 1999, between us and
Firstar Bank, N.A., as trustee and paying agent. The following summary of some
provisions of the indenture, the new senior notes and the guarantees is not
complete, and is qualified in its entirety by reference to the provisions of the
indenture. A copy of the indenture and the supplemental indenture have been
filed as exhibits to the registration statement that includes this prospectus.
The holders of new senior notes are entitled to the benefits of and are bound by
all the provisions of the indenture.

GENERAL

     The indenture does not limit the aggregate principal amount of debt
securities that may be issued under it and provides that debt securities may be
issued from time to time in one or more series as provided in a supplemental
indenture or a resolution of our Board of Directors. The new senior notes will
be fully and unconditionally guaranteed by Alliant Energy Corporation, will be
issued in the aggregate principal amount of $250,000,000 and will mature on
November 9, 2009, at their principal amount unless redeemed before that date.


     We will pay interest on the new senior notes at a rate of 7 3/8% per annum
from the most recent date to which interest has been paid on the existing senior
notes or, if no interest has been paid, from the date of issuance of the
existing senior notes. We will pay interest on the new senior notes semiannually
in arrears on May 9 and November 9 of each year, commencing on November 9, 2000,
until the principal amount has been paid or made available for payment, to the
persons in whose names the new senior notes are registered at the close of
business on May 1 or November 1, as the case may be, before each interest
payment date. Interest on the new senior notes will be computed on the basis of
a 360-day year of twelve 30-day months. The principal of and interest on the new
senior notes will be payable in U.S. dollars or in such other coin or currency
of the United States that at the time of payment is legal tender for the payment
of public and private debts.


FULL AND UNCONDITIONAL GUARANTEE

     Alliant Energy Corporation has agreed to fully and unconditionally
guarantee the payment of the principal of, and premium, if any, or interest on,
the new senior notes as these items become due and payable, whether at maturity,
upon redemption or otherwise, according to the terms of the new senior notes and
the indenture. Alliant Energy Corporation will determine, at least one business
day prior to the date upon which a payment of principal of, and premium, if any,
or interest on, the new seniors notes is due and payable, whether we have
available the funds to make these payments as they become due and payable. If we
fail to pay principal, premium, if any, or interest, then Alliant Energy
Corporation will cause these payments to be made as they become due and payable,
whether at maturity, upon redemption, or otherwise, as if these payments were
made by us. Alliant Energy Corporation's obligations will be unconditional
regardless of the validity or enforceability of, or the absence of any action to
enforce, the new senior notes or the indenture, any waiver or consent by a
holder of new senior notes, the recovery of any judgment against us or any
action to enforce a judgment against us. Alliant Energy Corporation will be
subrogated to all rights of a holder of new senior notes against us with respect
to any amounts paid by Alliant Energy Corporation pursuant to the guarantee.

RANKING

     The new senior notes will be senior, unsecured and unsubordinated
obligations of ours ranking equally and ratably with all our other senior,
unsecured and unsubordinated obligations. The guarantees will be unsecured
obligations of Alliant Energy Corporation and will rank equally with all other
unsecured and unsubordinated indebtedness of Alliant Energy Corporation. Because
we are a holding company and conduct substantially all of our operations through
our subsidiaries, the rights of our creditors, including

                                       29
<PAGE>   31

those under the new senior notes, to participate in any distributions of the
assets of any of our subsidiaries or joint ventures, upon liquidation or
reorganization or otherwise, are necessarily subject, and therefore will be
effectively subordinated, to the prior claims of creditors of any of our
subsidiaries or joint ventures, except to the extent our claims as a creditor
may be recognized.

     In addition, because Alliant Energy Corporation is a holding company which
conducts substantially all of its operations through subsidiaries, including us,
the right of Alliant Energy Corporation, and hence the right of creditors of
Alliant Energy Corporation, including holders of the new senior notes through
the guarantees, to participate in any distribution of assets of any subsidiary
upon its liquidation or reorganization or otherwise is necessarily subject to
the prior claims of creditors of such subsidiaries, except to the extent that
claims of Alliant Energy Corporation itself as a creditor of the subsidiary may
be recognized.

     The new senior notes will also be effectively subordinated to all of our
future secured indebtedness and the related guarantees will be effectively
subordinated to all future secured indebtedness of Alliant Energy Corporation.

BOOK-ENTRY PROCEDURES AND FORM

  Global Notes: Book-Entry Form

     Except as provided below, the new senior notes will be issued in fully
registered book-entry form and will be represented by one or more global notes.
The global notes will be deposited with, or on behalf of, The Depositary Trust
Company of New York City and registered in the name of a nominee of DTC.

     We expect that pursuant to procedures established by DTC:

     - upon the issuance of the new senior notes in the form of one or more
       global notes, DTC or its custodian will credit, on its internal system,
       the principal amount of new senior notes of the individual beneficial
       interests represented by these global notes to the respective accounts of
       participants who have accounts with DTC and

     - ownership of beneficial interests in the global notes will be shown on,
       and the transfer of this ownership will be effected only through, records
       maintained by DTC or its nominee with respect to interests of
       participants and the records of participants with respect to interests of
       persons other than participants. Holders of senior notes may hold their
       interests in the global notes directly through DTC if they are
       participants in this system, or indirectly through organizations which
       are participants in this system. The laws of some states of the United
       States may require that certain purchasers of securities take physical
       delivery of the new senior notes in definitive certificated form. Such
       limits and such laws may impair the ability of such purchasers to own,
       transfer or pledge interests in the global notes.

     So long as DTC, or its nominee, is the registered owner or holder of new
senior notes, DTC or its nominee, as the case may be, will be considered the
sole owner or holder of new senior notes represented by the global notes for all
purposes under the indenture. No beneficial owner of an interest in the global
notes will be able to transfer that interest except in accordance with DTC's
procedures, in addition to those provided for under the indenture with respect
to the new senior notes.

     Payments of the principal of, and premium, if any, and interest on, the
global notes will be made to DTC or its nominee, as the case may be, as the
registered owner thereof. None of us, the trustee or any paying agent will have
any responsibility or liability for any aspect of the records relating to or
payments made on account of beneficial ownership interests in the global notes
or for maintaining, supervising or reviewing any records relating to such
beneficial ownership interest.

     We expect that DTC or its nominee, upon receipt of any payment of principal
of and premium, if any, and interest on the global notes, will credit
participants' accounts with payments in amounts proportionate to their
respective beneficial interests in the principal amount of the global notes as
shown on the records of DTC or its nominee. We also expect that payments by
participants to owners of
                                       30
<PAGE>   32

beneficial interests in the global notes held through such participants will be
governed by standing instructions and customary practice, as is now the case
with securities held for the accounts of customers registered in the names of
nominees for such customers. These payments will be the responsibility of such
participants. Transfers between participants in DTC will be effected in the
ordinary way through DTC's settlement system in accordance with DTC rules and
will be settled in same day funds.

     DTC has advised us that it will take any action permitted to be taken by a
holder of new senior notes only at the direction of one or more participants to
whose account the DTC interests in the global notes are credited and only in
respect of such portion of the aggregate principal amount of new senior notes as
to which such participant or participants has or have given such direction.

     DTC has advised us as follows: DTC is a limited purpose trust company
organized under the laws of the State of New York, a member of the Federal
Reserve System, a "clearing corporation" within the meaning of the Uniform
Commercial Code and a "clearing agency" registered pursuant to the provisions of
Section 17A of the Securities Exchange Act of 1934. DTC was created to hold
securities for its participants and facilitate the clearance and settlement of
securities transactions between participants through electronic book-entry
changes in accounts of its participants, thereby eliminating the need for
physical movement of certificates. Participants include securities brokers and
dealers, banks, trust companies and clearing corporations and some other
organizations. Indirect access to the DTC system is available to others such as
banks, brokers, dealers and trust companies that clear through or maintain a
custodial relationship with a participant, either directly or indirectly.

     Although DTC has agreed to the foregoing procedures in order to facilitate
transfers of interests in the global notes among participants of DTC, it is
under no obligation to perform such procedures, and such procedures may be
discontinued at any time. None of us, the trustee or any of our respective
agents will have any responsibility for the performance by DTC or its
participants or indirect participants of their respective obligations under the
rules and procedures governing their operations, including maintaining,
supervising or reviewing the records relating to, payments made on account of,
beneficial ownership interests in global notes.

     According to DTC, the foregoing information with respect to DTC has been
provided to its participants and other members of the financial community for
informational purposes only and is not intended to serve as a representation,
warranty or contract modification of any kind.

  Certificated Notes

     We will issue new senior notes in certificated form in exchange for global
notes if:

     -  DTC or any successor depositary notifies us that it is unwilling or
        unable to continue as a depositary for the global notes or ceases to be
        a "clearing agency" registered under the Securities Exchange Act of 1934
        and a successor depositary is not appointed by us within 90 days of such
        notice,

     -  an event of default under the new senior notes has occurred and is
        continuing, or

     -  we determine that the new senior notes will no longer be represented by
        global notes.

     The holder of a new senior note in certificated form may transfer such note
by surrendering it at the office or agency maintained by us for such purpose in
Milwaukee, Wisconsin or New York, New York.

     A holder of a new senior note may request that its new senior note be
issued in certificated form and may request at any time that its interest in a
global note be exchanged for a new senior note in certificated form. New senior
notes in certificated form may also be issued in exchange for new senior notes
represented by the global notes if no successor depositary is appointed by us as
described above or in some other circumstances set forth in the indenture.

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<PAGE>   33

PURCHASE AND CANCELLATION

     We may at any time purchase new senior notes in the open market or
otherwise at any price, subject to applicable U.S. securities laws. Any purchase
by tender will be made available to all holders of new senior notes. Any new
senior notes so purchased must be promptly surrendered to the trustee for
cancellation.

     All new senior notes that are redeemed or purchased by us will promptly be
canceled. Any new senior notes in certificated form so canceled will be
forwarded to or to the order of the trustee and these new senior notes in
certificated form may not be reissued or resold.

COVENANTS

     Except as otherwise set forth under "-- Defeasance and Covenant Defeasance"
below, for so long as any new senior notes remain outstanding or any amount
remains unpaid on any of the new senior notes, we will comply with the terms of
the covenants set forth below.

  Payment of Principal and Interest

     We will duly and punctually pay the principal of and premium, if any, and
interest on the new senior notes in accordance with the terms of the new senior
notes and the indenture.

  Limitation on Liens

     The indenture provides that we will not, and we will not permit any of our
subsidiaries to issue, assume or guarantee any Debt if the Debt is secured by
any Lien upon any of our property or assets other than cash, without effectively
securing the outstanding new senior notes, together with any other indebtedness
then existing or thereafter created ranking equally with the new senior notes,
equally and ratably with the Debt. "Debt" is defined in the indenture as all of
our obligations evidenced by bonds, debentures, notes or similar evidences of
indebtedness in each case for money borrowed. "Lien" is defined in the indenture
as any mortgage, lien, pledge, security interest or other encumbrance. The term
"Lien" does not include any easements, rights-of-way, restrictions and other
similar encumbrances and encumbrances consisting of zoning restrictions, leases,
subleases, licenses, sublicenses, restrictions on the use of property or defects
in the title to property. The limitation on Liens does not apply to:

     -  Liens in existence on the date of original issuance of the new senior
        notes;

     -  any Lien created or arising over any property or assets which we or any
        of our subsidiaries acquire, construct or create, but only if:

       - the Lien secures only principal amounts, which may not exceed the cost
         of the acquisition, construction or creation, of Debt, together with
         any costs, expenses, interest and fees, incurred in connection with the
         acquisition, construction or creation of the property or assets or a
         guarantee given in connection with the acquisition, construction or
         creation of the property or assets,

       - the Lien is created or arises on or before 90 days after the completion
         of the acquisition, construction or creation of the property or assets
         and

       - the Lien is confined solely to the property or assets so acquired,
         constructed or created;

     -  any Lien to secure the Debt incurred by us or our subsidiaries in
        connection with a specifically identifiable project where the Lien
        relates and is confined to a property, including shares or other rights
        of ownership in the entities which own that property or project,
        involved in that project and acquired by us or our subsidiaries after
        the date of original issuance of the senior notes and the recourse of
        the creditors in respect of the Debt is limited to that project and
        property;

     -  any Lien securing amounts not more than 90 days overdue or otherwise
        being contested in good faith;
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<PAGE>   34

     -  rights of financial institutions to offset credit balances in connection
        with the operation of cash management programs established or the
        issuance of letters of credit for our or any of our subsidiaries'
        benefit;

     -  any Lien securing Debt incurred by us or any of our subsidiaries in
        connection with the financing of accounts receivable;

     -  any Lien incurred in the ordinary course of business, including any
        mechanics', materialmen's, carriers', workmen's, vendors' or other like
        Liens and any Liens securing amounts in connection with workers'
        compensation, unemployment insurance and other types of social security;

     -  any Lien upon specific items of our or any of our subsidiaries'
        inventory or other goods and proceeds securing our or any of our
        subsidiaries' obligations in respect of bankers' acceptances issued or
        created to facilitate the purchase, shipment or storage of inventory or
        other goods;

     -  any Lien incurred 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
        us or any of our subsidiaries in the ordinary course of business;

     -  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 us or any of our subsidiaries in
        respect of the hedging or management of risks under transactions
        involving any derivative instrument of any kind;

     -  any Lien arising out of title retention or like provisions in connection
        with the purchase of goods and equipment by us or any of our
        subsidiaries in the ordinary course of business;

     -  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 us or any of our
        subsidiaries in the ordinary course of business;

     -  Liens on any property or assets acquired from an entity with which we or
        any of our subsidiaries merge and that 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;

     -  any Lien on any property or assets existing at the time of acquisition
        by us or any of our subsidiaries 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;

     -  Liens required by any contract or statute in order to permit us or any
        of our subsidiaries to perform any contract or subcontract made by us or
        any of our subsidiaries with a governmental entity or governmental unit,
        or to secure payments by us or any of our subsidiaries to a governmental
        unit under the provisions of any contract or statute;

     -  any Lien securing industrial revenue, development or similar bonds
        issued by us or any of our subsidiaries or for our or any of our
        subsidiaries' benefit, provided that these bonds are nonrecourse to us
        or any of our subsidiaries;

     -  any Lien securing taxes or assessments or other applicable governmental
        charges or levies;

     -  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 that legal process is effectively stayed and the claims
        secured by the Lien are being contested in good faith and 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;

                                       33
<PAGE>   35

     -  any Lien arising by operation of law or by order of a court or any Lien
        arising by an agreement of similar effect, including judgment liens; or

     -  any extension, renewal or replacement of any Liens referred to in the
        clauses 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 those properties or
        assets.

     Although the indenture limits our and our subsidiaries' ability to incur
Liens as set forth above, the indenture nevertheless provides that we or our
subsidiaries may create or permit to subsist Liens over any of our and our
subsidiaries' property or assets so long as the aggregate amount of Debt secured
by all Liens that we or our subsidiaries incur, excluding the amount of Debt
secured by Liens set forth in the clauses above, does not exceed 10% of Alliant
Energy Corporation's Consolidated Net Tangible Assets. "Consolidated Net
Tangible Assets" is defined in the indenture as the total of all assets,
including revaluations thereof as a result of commercial appraisals, price level
restatement or otherwise, appearing on the most recent consolidated balance
sheet of Alliant Energy Corporation as of the date of determination, net of
applicable reserves and deductions, but excluding goodwill, trade names,
trademarks, patents, unamortized debt discount and all other like intangible
assets, less the aggregate of the consolidated current liabilities of Alliant
Energy Corporation appearing on such balance sheet.

  Limitation on Sale and Lease-Back Transactions

     The indenture provides that we will not enter into any arrangement with any
entity providing for the lease by us of any of the assets that we have sold or
transferred or that we have agreed to sell or transfer to that entity unless:

     -  the transaction involves a lease for a temporary period not to exceed
        three years;

     -  the transaction is between us and one of our affiliates;

     -  we would be entitled to incur Debt secured by a Lien on the assets or
        property involved in the transaction at least equal to the Attributable
        Debt with respect to the transaction, without equally and ratably
        securing the senior notes, as described under "-- Limitation on Liens"
        above, other than as described in the second paragraph of that
        description;

     -  we enter into the transaction within 270 days after our initial
        acquisition of the assets or property subject to the transaction;

     -  the aggregate amount of all Attributable Debt with respect to all sale
        and lease-back transactions then in effect does not exceed 10% of
        Alliant Energy Corporation's Consolidated Net Tangible Assets; or

     -  within 12 months preceding the sale or transfer or 12 months following
        the sale or transfer, regardless of whether we make any sale or
        transfer, we apply, in the case of a sale or transfer for cash, an
        amount equal to the net proceeds of the sale or transfer and, in the
        case of a sale or transfer other than for cash, an amount equal to the
        fair value of the assets so leased at the time that we enter into the
        arrangement, as determined by our Board of Directors,

       - to the retirement of Debt, incurred or assumed by us which by its terms
         matures at, or is extendible or renewable at the option of the obligor
         to, a date more than 12 months after the date of incurring, assuming or
         guaranteeing such Debt; or

       - to an investment in any of our assets.

     "Attributable Debt" is defined in the indenture as, with respect to any
particular sale and lease-back transaction, at the time of determination, the
present value of the obligation of the lessee for net rental payments during the
remaining term of the lease included in the sale and lease-back transaction,
including any period for which such lease has been extended or may, at the
option of the lessor, be extended. The
                                       34
<PAGE>   36

present value of this obligation is discounted at the rate of interest implicit
in the transaction determined in accordance with generally accepted accounting
principles.

  Consolidation, Merger, Conveyance, Sale or Lease

     The indenture provides that we may, without the consent of any holders of
the new senior notes, consolidate or merge with, or convey, transfer or lease
substantially all of our property and assets to, another U.S. entity so long as:

     -  if we are not the surviving entity, the surviving entity expressly
        assumes by supplemental indenture all of our applicable obligations
        under the new senior notes and the indenture;

     -  immediately after giving effect to the transaction, no event of default
        under the new senior notes and no event which, after notice or lapse of
        time, would become an event of default under the new senior notes, has
        occurred and is continuing; and

     -  either we or our successor delivers to the trustee an officers'
        certificate and an opinion of counsel stating that the consolidation,
        merger, conveyance, transfer or lease, and if a supplemental indenture
        is required by the transaction, the supplemental indenture, comply with
        the indenture and all conditions precedent in the indenture relating to
        such transaction.

     In addition, we may assign and delegate all of our rights and obligations
under the indenture, the new senior notes, the supplemental indenture and all
other related documents, agreements and instruments to Alliant Energy
Corporation or a subsidiary of Alliant Energy Corporation, any person that owns
all of our capital stock or any person that owns all of the capital stock of a
person that owns all of our capital stock. Upon the assumption of these rights
and obligations by that person, we will be automatically released from the
obligations, provided that immediately after giving effect to the transaction,
no event of default under the new senior notes, and no event which, after notice
or lapse of time, would become an event of default under the new senior notes,
has occurred and is continuing.

     The indenture also provides that Alliant Energy Corporation may, without
the consent of any holders of the new senior notes, consolidate or merge with,
or convey, transfer or lease substantially all of its property and assets to,
another U.S. entity so long as:

     -  if Alliant Energy Corporation is not the surviving entity, the surviving
        entity assumes by supplemental indenture all of Alliant Energy
        Corporation's obligations under the guarantees and the indenture;

     -  immediately after giving effect to the transaction, no event of default
        under the new senior notes, and no event which, after notice or lapse of
        time, would become an event of default under the new senior notes, has
        occurred and is continuing; and

     -  either Alliant Energy Corporation or the successor person delivers to
        the trustee an officers' certificate and an opinion of counsel stating
        that the consolidation, merger, conveyance, transfer or lease, and if a
        supplemental indenture is required by the transaction, the supplemental
        indenture, comply with the indenture and all conditions precedent in the
        indenture, relating to these transactions.

  Money For Securities Payments To Be Held In Trust

     The indenture provides that if we at any time act as our own paying agent
with respect to the new senior notes, we will, on or before each due date of the
principal of, or any premium or interest on, any of the new senior notes,
segregate and hold in trust for the benefit of the persons entitled a sum in the
currency in which the new senior notes are payable sufficient to pay the
principal or any premium or interest due until such sums are paid or otherwise
disposed of. We will promptly notify the trustee of our action or failure to
act.

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<PAGE>   37

     Whenever we have one or more paying agents for any series of debt
securities, we will, on or prior to each due date of the principal of, or any
premium or interest on any series of debt securities, deposit with any paying
agent a sum sufficient to pay the principal or any premium or interest due, the
sum to be held in trust for the benefit of the persons entitled. Unless the
paying agent is the trustee, we will promptly notify the trustee of our action
or failure to act.

     We will cause each paying agent for each series of debt securities, if
other than the trustee, to execute and deliver to the trustee an agreement that
requires the paying agent:

     -  to hold all sums held by it for the payment of the principal of, or any
        premium or interest on, any series of debt securities in trust for the
        benefit of the persons entitled until such sums are paid or otherwise
        disposed of as provided in the indenture;

     -  to give the trustee notice of any default by us or Alliant Energy
        Corporation in the making of any payment of principal, any premium or
        interest on, any series of debt securities; and

     -  at any time during the continuance of the default, upon the written
        request of the trustee, pay to the trustee all sums held in trust by it.

     We or Alliant Energy Corporation may at any time pay, or direct any paying
agent to pay, to the trustee all sums held in trust by us or the paying agent.
These sums will be held by the trustee upon the same terms as those applicable
to us or the paying agent. Upon payment by the paying agent to the trustee, the
paying agent will be released from all further liability with respect to such
sums.

     Except as otherwise provided in the indenture, any money deposited with the
trustee or the paying agent, or held by us, in trust for the payment of the
principal of, or any premium or interest on, any series of debt securities and
remaining unclaimed for two years after that principal, premium or interest has
become due and payable will be discharged from such trust. The holder of the new
senior note will thereafter, as an unsecured general creditor, look only to us
or Alliant Energy Corporation, as the case may be, for payment, and all
liability of the trustee or the paying agent with respect to the trust money,
and all liability of us as trustee thereof, will cease. However, the trustee or
the paying agent may at our expense cause to be published once, in an authorized
newspaper or mailed to holders of the new senior notes, or both, notice that
such money remains unclaimed and that, after a date specified, which will not be
less than 30 days from the date of the publication or mailing nor later than two
years after the principal and any premium or interest have become due and
payable, any unclaimed balance of such money then remaining will be repaid to us
or Alliant Energy Corporation, as the case may be.

  Company And Guarantor Statements As To Compliance; Notice Of Defaults

     We and Alliant Energy Corporation will each deliver to the trustee, within
120 days after the end of each fiscal year, a written statement signed by our
respective principal executive officer, principal financial officer or principal
accounting officer, stating that:

     -  a review of our respective activities during the year and of our
        respective performances under the indenture has been made under such
        officer's supervision, and

     -  to the best of such officer's knowledge, based on that review,

       - we or Alliant Energy Corporation, as the case may be, have complied
         with all the conditions and covenants imposed on each of us by the
         indenture throughout the year, or, if there has been a default in the
         fulfillment of any condition or covenant, specifying each default known
         to such officer and its nature and status, and

       - no event has occurred and is continuing which is, or after notice or
         lapse of time would become, an event of default under the new senior
         notes, or, if such an event has occurred and is continuing, specifying
         each such event known to such officer and its nature and status.

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<PAGE>   38

     We and Alliant Energy Corporation will deliver to the trustee, within five
days after its occurrence, written notice of any event of default under the new
senior notes or any event which after notice or lapse of time would become an
event of default.

MODIFICATION OF THE INDENTURE

     We, Alliant Energy Corporation and the trustee may modify and amend the
indenture or any supplemental indenture or the rights of the holders of the debt
securities of each series to be affected with the consent of the holders of more
than 50% of the principal amount of the outstanding debt securities of each
affected series, with each series voting as a class. These majority holders may
also waive compliance by us or Alliant Energy Corporation with any provision of
the indenture, any supplemental indenture or the debt securities of any series.
However, without the consent of a holder of each debt security affected, an
amendment or waiver may not:

     -  reduce the amount of debt securities whose holders must consent to an
        amendment or waiver;

     -  change the rate or the time for payment of interest;

     -  change the principal or the fixed maturity;

     -  waive a default in the payment of principal, premium or interest;

     -  make any debt securities payable in a different currency;

     -  make any change in the provisions of the indenture concerning waiver of
        existing defaults, rights of holders of debt securities to receive
        payments or amendments and waivers with consent of holders of debt
        securities;

     -  impair the right to institute suit for the enforcement of any payment on
        or after the stated maturity of such payment or, in the case of
        redemption, on or after the redemption date; or

     -  modify or effect in any manner adverse to the holders the terms and
        conditions of Alliant Energy Corporation's obligations regarding due and
        punctual payment of principal of, or any premium or interest on, or any
        sinking fund requirements of, any debt securities subject to guarantees.

     We, Alliant Energy Corporation and the trustee may amend or supplement the
indenture without the consent of any holder of any of the debt securities:

     -  to cure any ambiguity, defect or inconsistency in the indenture, any
        supplemental indenture, the debt securities or guarantees;

     -  to provide for the assumption of all of our obligations under the debt
        securities, the indenture, or any supplemental indenture or of Alliant
        Energy Corporation's obligations under the guarantees and the indenture
        or any supplemental indenture by any corporation in connection with a
        merger or consolidation of us or Alliant Energy Corporation or transfer
        or lease of substantially all of our or Alliant Energy Corporation's
        property and assets;

     -  make any change that does not adversely affect the rights of any holder
        of debt securities;

     -  to add to the rights of holders of any of the debt securities;

     -  to secure any debt securities as provided under the heading "--
        Limitation on Liens";

     -  to evidence the succession of another person to us or Alliant Energy
        Corporation, and the assumption by the successor person of the covenants
        of us and Alliant Energy Corporation, as the case may be, provided in
        the indenture or the senior notes;

     -  to establish the form or terms of any debt securities;

     -  to evidence and provide for the acceptance of appointment under the
        indenture by a successor trustee with respect to the debt securities and
        to add to or change any of the provisions of the indenture necessary to
        facilitate the administration of the indenture by more than one trustee;
        or
                                       37
<PAGE>   39

     -  to supplement any of the provisions of the indenture to the extent
        necessary to permit or facilitate defeasance and discharge of any debt
        securities, provided that such action will not adversely affect the
        interests of any holder of any debt security in any material respect.

EVENTS OF DEFAULT

     Any one of the following is an event of default with respect to the senior
notes:

          (a) if we or Alliant Energy Corporation default in the payment of any
     interest on the senior notes, and such default continues for 30 days;

          (b) if we or Alliant Energy Corporation default in payment of
     principal of or premium, if any, on the senior notes when the same become
     due at maturity, upon redemption, by declaration or otherwise;

          (c) if we or Alliant Energy Corporation materially default in the
     performance or materially breach any of our respective covenants or
     obligations in the indenture, any supplemental indenture or the senior
     notes and this material default or breach continues for a period of 90 days
     after we or Alliant Energy Corporation receive written notice from the
     trustee or the holders of at least 25% in aggregate principal amount of the
     outstanding senior notes;

          (d) if we or Alliant Energy Corporation default in the payment of the
     principal of any bond, debenture, note or other indebtedness or in the
     payment of principal under any mortgage, indenture or instrument under
     which there may be issued or by which there may be secured or evidenced any
     indebtedness for money borrowed, which default for payment of principal is
     in an aggregate principal amount exceeding $25,000,000 when such
     indebtedness becomes due and payable, whether at maturity, upon redemption
     or acceleration or otherwise, if such default continues unremedied or
     unwaived for more than 30 business days and the time for payment of such
     amount has not been expressly extended;

          (e) our failure or the failure by Alliant Energy Corporation generally
     to pay our respective debts as they become due, or the admission in writing
     of our inability or Alliant Energy Corporation's inability to pay our
     respective debts generally, or the making of a general assignment for the
     benefit of our respective creditors, or the institution of any proceeding
     by or against Alliant Energy Corporation or us that is not dismissed within
     180 days from its commencement seeking to adjudicate us or Alliant Energy
     Corporation bankrupt or insolvent, or seeking liquidation, winding up,
     reorganization, arrangement, adjustment, protection, relief or composition,
     other than a solvent liquidation, winding up, reorganization, arrangement,
     adjustment, protection, relief or composition, of us or Alliant Energy
     Corporation or our respective debts under any law relating to bankruptcy,
     insolvency, reorganization, moratorium or relief of debtors, or seeking the
     entry of an order for relief or appointment of an administrator, receiver,
     trustee, intervenor or other similar official for us or Alliant Energy
     Corporation or for any substantial part of our property or the property of
     Alliant Energy Corporation, or the taking of any action by Alliant Energy
     Corporation or us to authorize any of the actions set forth in this clause;
     and

          (f) a material default in the performance or material breach by
     Alliant Energy Corporation of any covenant or obligation of Alliant Energy
     Corporation contained in the guarantee, and the continuance of such
     material default or breach for a period of 90 days after which we or
     Alliant Energy Corporation receive written notice from the trustee or the
     holders of at least 25% in aggregate principal amount of the senior notes.

     If an event of default with respect to the senior notes occurs and is
continuing, either the trustee or the holders of at least 25% in aggregate
principal amount of the outstanding senior notes may declare the principal
amount of the outstanding senior notes, and any interest accrued on the senior
notes, to be due and payable immediately by delivering a written notice to us
and Alliant Energy Corporation and to the trustee if given by the holders. At
any time after that declaration of acceleration has been made, but before a
judgment or decree for payment of money has been obtained, the holders of a
majority in
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<PAGE>   40

principal amount of all of the senior notes, by notice to the trustee, may
rescind this declaration and all its consequences if all events of default have
been cured or waived, other than the non-payment of principal of the outstanding
new senior notes which has become due solely by reason of the declaration of
acceleration, and that declaration of acceleration and its consequences will be
automatically annulled and rescinded.

     Holders of the new senior notes may not enforce the indenture, the new
senior notes or any guarantees, if applicable, unless:

     -  the holder has previously given written notice to the trustee of a
        continuing event of default under the senior notes with respect to the
        senior notes;

     -  the holders of not less than 25% in aggregate principal amount of the
        senior notes have made written request to the trustee to institute
        proceedings in respect of such event of default under the senior notes
        in its own name as trustee;

     -  the holder or holders have offered the trustee indemnity satisfactory to
        the trustee against the costs, expenses and liabilities to be incurred
        in compliance with such request;

     -  the trustee, for 60 days after its receipt of such notice, request and
        offer of indemnity, has failed to institute any such proceedings; and

     -  no direction inconsistent with such written request has been given to
        the trustee during the 60-day period by the holders of a majority of the
        outstanding aggregate principal amount of the senior notes.

     However, these limitations do not apply to a suit instituted by a holder of
any new senior notes for the enforcement of the payment of the principal of or
premium, if any, or interest on the new senior notes on or after the applicable
due date specified in the new senior notes.

     If the trustee collects any money pursuant to an event of default under the
senior notes, it will pay out the money in the following order:

     -  first, to the trustee for amounts to it as compensation for its services
        and any indemnities owed to it;

     -  second, to holders of the senior notes in respect of which or for the
        benefit of which this money has been collected for amounts due and
        unpaid on the senior notes for principal and interest, ratably, without
        preference or priority of any kind, according to the amounts due and
        payable on the senior notes for principal and interest; and

     -  third, to the person or persons lawfully entitled this money, or as a
        court of competent jurisdiction may direct.

     The trustee may fix a record date with respect to registered securities and
payment date for any such payment to holders of the senior notes. This record
date will not be less than 10 days nor more than 60 days prior to the applicable
payment date.

OPTIONAL REDEMPTION

     We may redeem the new senior notes at our 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 new senior notes, at a price equal to
the greater of:

     - 100% of the principal amount of the new senior notes being redeemed; and

     - the sum of the present values of the principal amount of the new senior
       notes to be redeemed and the remaining scheduled payments of interest on
       the new senior notes from the redemption date to November 9, 2009,
       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

                                       39
<PAGE>   41

       equal to the Treasury Yield plus 20 basis points, plus accrued interest
       on the new senior notes to the redemption date.

     "Treasury Yield" means, with respect to any redemption date, the annual
rate equal to the semi-annual equivalent yield to maturity of the Comparable
Treasury Issue, assuming a price for the Comparable Treasury Issue expressed as
a percentage of its principal amount equal to the Comparable Treasury Price for
such redemption date.

     "Comparable Treasury Issue" means the United States treasury security
selected by an Independent Investment Banker as having a maturity comparable to
the remaining term of the senior notes to be redeemed that would be utilized, at
the time of selection and in accordance with customary financial practice, in
pricing new issues of corporate debt securities of comparable maturity to the
remaining term of the senior notes.

     "Comparable Treasury Price" means, with respect to any date of redemption,

     - the average of the bid and asked prices for the Comparable Treasury Issue
       expressed in each case as a percentage of its principal amount on the
       third business day preceding the redemption date, as set forth in the
       daily statistical release published by the Federal Reserve Bank of New
       York and designated "Composite 3:30 p.m. Quotations for U.S. Government
       Securities" or

     - if this release is not published or does not contain such prices on the
       business day in question, the Reference Treasury Dealer Quotation for the
       redemption date.

     "Independent Investment Banker" means an independent investment banking
institution of national standing appointed by us and reasonably acceptable to
the trustee.

     "Reference Treasury Dealer Quotation" means, with respect to the Reference
Treasury Dealer and redemption date, the average, as determined by us, of the
bid and asked prices for the Comparable Treasury Issue expressed in each case as
a percentage of its principal amount and quoted in writing to us by the
Reference Treasury Dealer at 5:00 p.m. on the third business day preceding the
redemption date.

     "Reference Treasury Dealer" means a primary United States government
securities dealer in New York City appointed by us and reasonably acceptable to
the trustee.

     Notice of redemption will be mailed by first class mail at least 30 but not
more than 60 days before the redemption date to each holder of the new senior
notes to be redeemed at its registered address.

     If fewer than all the new senior notes are to be redeemed, selection of new
senior notes for redemption will be made by the trustee in any manner the
trustee deems fair and appropriate and that complies with applicable legal and
securities exchange requirements.

     Unless we default in payment of the redemption price, from and after the
date of redemption, the new senior notes or portions thereof called for
redemption will cease to bear interest, and the holders of the new senior notes
will have no right in respect of the new senior notes except the right to
receive the redemption price.

DEFEASANCE AND COVENANT DEFEASANCE

     The indenture provides that we and Alliant Energy Corporation may elect:

     - to be discharged from any and all of our respective obligations in
       respect of the new senior notes ("defeasance"), except for the
       obligations to register the transfer or exchange of the new senior notes,
       replace stolen, lost or mutilated new senior notes, maintain paying
       agencies and hold moneys for payments in trust or

     - not to comply with some covenants ("covenant defeasance") of the
       indenture with respect to the new senior notes described above under "--
       Covenants"

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<PAGE>   42

If we and Alliant Energy Corporation irrevocably deposit with the trustee money
or U.S. Government Obligations or a combination of money or U.S. Government
Obligations, in an amount sufficient, together with interest paid on the U.S.
Government Obligations, to pay, when due, the principal of and premium, if any,
and interest on the outstanding new senior notes to maturity or redemption or an
installment of interest. We and Alliant Energy Corporation must satisfy certain
other conditions before we may effect defeasance or covenant defeasance. These
conditions include:

     -  that no event of default under the senior notes or event, which with
        notice or lapse of time would become an event of default with respect to
        the new senior notes, will have occurred and be continuing on the date
        of the deposit or insofar as an event of default described in clause (e)
        of the first paragraph under "-- Events of Default" is concerned, at any
        time during the period ending on the 181st day after the date of the
        deposit; and

     -  that the defeasance or covenant defeasance will not result in the breach
        or violation of, or constitute a default under, the indenture or any
        other material agreement or instrument under which we are bound or under
        which Alliant Energy Corporation is bound.

     To exercise any such option, we or Alliant Energy Corporation will be
required to deliver to the Trustee:

     - an opinion of independent counsel of recognized standing to the effect
       that the holders of the new senior notes will not recognize income, gain
       or loss for United States federal income tax purposes as a result of such
       deposit, and will be subject to United States federal income tax on the
       same amounts, in the same manner and at the same times as would have been
       the case absent the deposit, which in the case of defeasance must be
       based on a change in law or a published ruling by the United States
       Internal Revenue Service, and the deposit will not result in us or
       Alliant Energy Corporation being deemed an "investment company" required
       to be registered under the Investment Company Act of 1940 and

     - an officer's certificate as to compliance with all conditions precedent
       provided for in the indenture relating to the satisfaction and discharge
       of the new senior notes.

     If we or Alliant Energy Corporation wish to deposit or cause to be
deposited money or U.S. Government Obligations to pay or discharge the principal
of, premium, if any, and interest on the outstanding new senior notes to and
including a redemption date on which all of the outstanding new senior notes are
to be redeemed, the redemption date will be irrevocably designated by a
resolution of our Board of Directors or a resolution of the Board of Directors
of Alliant Energy Corporation delivered to the Trustee on or prior to the date
of deposit of such money or U.S. Government Obligations, and such Board
resolution will be accompanied by an irrevocable notice of the defeasance to the
trustee.

     If the trustee is unable to apply any money or U.S. Government Obligations
deposited in trust to effect a defeasance or covenant defeasance by reason of
any order or judgment of any court or governmental authority enjoining,
restraining or otherwise prohibiting such application, then any obligations from
which we or Alliant Energy Corporation had been discharged or released will be
revived and reinstated as though no such deposit of moneys in trust had
occurred, until the time that the trustee is permitted so to apply all of the
money or U.S. Government Obligations deposited in trust.

     "U.S. Government Obligations" means direct obligations of the United States
for the payment of which its full faith and credit is pledged, or obligations of
a person controlled or supervised by and acting as an agency or instrumentality
of the United States and the payment of which is unconditionally guaranteed by
the United States, and will also include a depository receipt issued by a bank
or trust company as custodian with respect to any U.S. Government Obligation or
a specific payment of interest on or principal of any U.S. Government Obligation
held by a custodian for the account of a holder of a depository receipt.
However, except as required by law, a custodian is not authorized to make any
deduction from the amount payable to the holder of any depository receipt from
any amount received by the custodian in respect of the U.S. Government
Obligation or the specific payment of interest on or principal of the U.S.
Government Obligation evidenced by a depository receipt.
                                       41
<PAGE>   43

PAYMENT AND PAYING AGENT

     We have appointed the trustee to act as paying agent with respect to the
new senior notes. We may at any time designate additional paying agents or
rescind the designation of any paying agents or approve a change in the office
through which any paying agent acts, except that we will be required to maintain
a paying agent in each place of payment for the new senior notes.

     All moneys paid by us to the paying agent for the payment of the principal
of, or premium, if any, or interest on, any new senior notes that remain
unclaimed at the end of two years after such principal, premium, if any, or
interest has become due and payable will be repaid to us and the holder of the
new senior notes will thereafter look only to us for payment of any such
amounts.

GOVERNING LAW

     The indenture and the new senior notes will be governed by, and construed
in accordance with, the laws of the State of Wisconsin.

                                       42
<PAGE>   44

                UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

     THIS SUMMARY IS OF A GENERAL NATURE AND IS INCLUDED SOLELY FOR
INFORMATIONAL PURPOSES. IT IS NOT INTENDED TO BE, NOR SHOULD IT BE CONSTRUED AS
BEING, LEGAL OR TAX ADVICE. NO REPRESENTATION WITH RESPECT TO THE CONSEQUENCES
TO ANY PARTICULAR PURCHASER OF THE NEW SENIOR NOTES IS MADE. PROSPECTIVE
PURCHASERS SHOULD CONSULT THEIR OWN TAX ADVISORS WITH RESPECT TO THEIR
PARTICULAR CIRCUMSTANCES.

     The following is a discussion of the material United States federal income
tax consequences to a beneficial owner of new senior notes (a "United States
Holder") who is:

     - a citizen or resident of the United States,

     - a corporation, partnership or other entity treated as a corporation or a
       partnership for United States federal income tax purposes created or
       organized in or under the laws of the United States, any state thereof or
       the District of Columbia,

     - an estate whose income is subject to United States federal income tax
       regardless of its source, or

     - a trust if a court within the United States is able to exercise primary
       supervision over the administration of the trust and one or more United
       States persons have the authority to control all substantial decisions of
       the trust.

     The following summary deals only with new senior notes held as capital
assets by purchasers at the issue price who are United States Holders and not
with special classes of holders, such as dealers in securities or currencies,
financial institutions, life insurance companies, tax-exempt entities, persons
holding new senior notes as a hedge against or which are hedged against currency
risks, and persons whose functional currency is not the U.S. dollar. Persons
considering the purchase of new senior notes should consult their own tax
advisors concerning these matters and as to the tax treatment under foreign,
state and local tax laws and regulations. We cannot provide any assurance that
the Internal Revenue Service will not challenge the conclusions stated below. We
have not sought and will not seek a ruling from the IRS on any of the matters
discussed below.

     This discussion is based upon the Internal Revenue Code of 1986, Treasury
Regulations, IRS rulings and pronouncements and judicial decisions now in
effect, all of which are subject to change at any time. Changes in this area of
law may be applied retroactively in a manner that could cause the tax
consequences to vary substantially from the consequences described below,
possibly adversely affecting a United States Holder. The authorities on which
this discussion is based are subject to various interpretations, and it is
therefore possible that the federal income tax treatment of the purchase,
ownership and disposition of the new senior notes may differ from the treatment
described below.

CONSEQUENCES OF THE EXCHANGE OFFER TO EXCHANGING AND NONEXCHANGING HOLDERS

     The exchange of an existing senior note for a new senior note pursuant to
the exchange offer will not be taxable to an exchanging United States Holder for
federal income tax purposes. As a result, an exchanging United States Holder
will not recognize any gain or loss on the exchange; the holding period for the
new senior note will include the holding period for the existing senior note;
and the basis of the new senior note will be the same as the basis for the new
senior note.

     The exchange offer will result in no federal income tax consequences to a
nonexchanging United States Holder of existing senior notes.

GENERAL

     A United States Holder using the accrual method of accounting for federal
income tax purposes is required to include interest paid or accrued on the new
senior notes in ordinary income as interest accrues, while a United States
Holder using the cash receipts and disbursements method of accounting for
federal income tax purposes must include interest in ordinary income when
payments are received, or made available for receipt, by the United States
Holder.

                                       43
<PAGE>   45

     Although the existing senior notes were issued at a discount of 1.2% per
existing senior note to the initial purchasers, such discount is not considered
to be original issue discount for tax purposes. However, the existing senior
notes provide for the payment of additional amounts of interest under certain
circumstances and therefore both the existing and new senior notes are subject
to the Treasury Regulations that apply to debt instruments that provide for one
or more contingent payments. For purposes of determining whether the existing
senior notes were issued with original issue discount, we intend to take the
position that the existing senior notes did not, as of the issue date, represent
contingent payment debt because the likelihood of paying an increased rate of
interest as a result of us or Alliant Energy Corporation defaulting under the
registration rights agreement was remote. Accordingly, both the existing and new
senior notes will not be considered to be issued with original issue discount. A
United States Holder may not take a contrary position unless such contrary
position is disclosed in the proper manner to the IRS. United States Holders
should consult their tax advisors regarding the tax consequences of the new
senior notes being treated as contingent payment debt.

     If the IRS successfully asserts that these contingent payments were not
remote as of the issue date, the amount and timing of the interest income that a
United States Holder is required to include in taxable income may have to be
redetermined and any gain or loss on a sale, exchange, redemption or retirement
of the new senior notes, may be recharacterized as ordinary income. If the
amount and timing of interest income required to be included in taxable income
is redetermined, then a United States Holder, regardless of the United States
Holder's method of accounting, may be required to include in taxable income
interest in excess of the coupon amount of interest received periodically over
the term of the new senior notes as its accrues, which may result in the
recognition of interest income prior to the receipt of the coupon amount of
interest.

SALE, EXCHANGE, REDEMPTION OR RETIREMENT OF NEW SENIOR NOTES

     Upon the sale, exchange, redemption or retirement of a new senior note, a
United States Holder will generally recognize capital gain or loss equal to the
difference between the amount realized and the United States Holder's tax basis
in the new senior note. For these purposes, the amount realized will not include
any amounts attributable to accrued and unpaid interest. A United States
Holder's tax basis in a new senior note will generally be its cost. That capital
gain or loss will generally be long-term capital gain or loss if the new senior
notes were held for more than one year; otherwise, the capital gain or loss will
be short-term.

ASSUMPTION OF THE NEW SENIOR NOTES

     An assumption of our obligations under the new senior notes may be deemed
for United States federal income tax purposes to be an exchange of the new
senior notes for new debt instruments resulting in the recognition of taxable
gain or loss to a United States Holder and possibly other adverse United States
tax consequences. Investors should consult their tax advisors regarding the
United States federal, state, local and foreign tax consequences of such an
assumption.

WITHHOLDING TAXES AND REPORTING REQUIREMENTS

     Interest payments and payments of principal and any premium with respect to
a new senior note will be reported to the extent required by the Internal
Revenue Code to the United States Holders and the IRS. These amounts will
ordinarily not be subject to withholding of United States federal income tax.
However, a backup withholding tax at a rate of 31% will apply to these payments
if a United States Holder fails to properly certify to us or our agent the
United States Holder's taxpayer identification number and other information, or
fails to report all interest and dividends required to be reported on its
federal income tax returns, or otherwise fails to establish, in the manner
prescribed by law, an exemption from backup withholding. Any amount withheld
under backup withholding is allowable as a credit against the United States
Holder's federal income tax liability, provided that person furnishes the
required information to the IRS.

                                       44
<PAGE>   46

     New IRS regulations will generally be applicable to payments made after
December 31, 1999. In general, these regulations do not significantly alter the
substantive withholding and information reporting requirements but unify and
clarify current procedures. Under the new regulations, special rules apply which
permit the shifting of primary responsibility for withholding to some financial
intermediaries acting on behalf of beneficial owners. United States Holders of
new senior notes should consult with their own tax advisors regarding the
application of the backup withholding rules to their particular situation, the
availability of exemption therefrom, the procedure for obtaining such an
exemption, if available, and the impact of the new regulations with respect to
new senior notes.

                                       45
<PAGE>   47

                              PLAN OF DISTRIBUTION

     Each broker-dealer that receives new senior notes for its own account as a
result of market-making activities or other trading activities in connection
with the exchange offer must acknowledge that it will deliver a prospectus in
connection with any resale of these new senior notes. This prospectus, as it may
be amended or supplemented from time to time, may be used by a broker-dealer in
connection with resales of new senior notes received in exchange for existing
senior notes where such existing senior notes were acquired as a result of
market-making activities or other trading activities.

     We will not receive any proceeds in connection with the exchange offer or
any sale of new senior notes by broker-dealers. New senior notes received by
broker-dealers for their own account pursuant to the exchange offer may be sold
from time to time in one or more transactions in the over-the-counter market, in
negotiated transactions, through the writing of options on the new senior notes
or a combination of these methods of resale, at market prices prevailing at the
time of resale, at prices related to such prevailing market prices or negotiated
prices. Any resale may be made directly to purchasers or to or through brokers
or dealers who may receive compensation in the form of commissions or
concessions from any such broker-dealers or the purchasers of any such new
senior notes. Any broker-dealer that resells new senior notes that were received
by it for its own account pursuant to the exchange offer and any broker-dealer
that participates in a distribution of such new senior notes may be deemed to be
an "underwriter" within the meaning of the Securities Act and any profit on any
such resale of new senior notes and any commissions or concessions received by
any such persons may be deemed to be underwriting compensation under the
Securities Act. The letter of transmittal states that by acknowledging that it
will deliver, and by delivering, a prospectus, a broker-dealer will not be
deemed to admit that it is an "underwriter" within the meaning of the Securities
Act. See "The Exchange Offer -- Resales of the New Senior Notes."

                                       46
<PAGE>   48

                                 LEGAL MATTERS

     Foley & Lardner of Milwaukee, Wisconsin will issue an opinion about some
legal matters with respect to the new senior notes.

                                    EXPERTS

     The audited financial statements and schedules incorporated by reference in
this prospectus and elsewhere in the registration statement have been audited by
Arthur Andersen LLP, independent public accountants, as indicated in their
reports with respect thereto, and are included herein in reliance upon the
authority of said firm as experts in giving said reports.

                                       47
<PAGE>   49

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

                                  $250,000,000

                     [ALLIANT ENERGY RESOURCES, INC. LOGO]

                         ALLIANT ENERGY RESOURCES, INC.

                        NEW 7 3/8% SENIOR NOTES DUE 2009
                         UNCONDITIONALLY GUARANTEED BY

                           ALLIANT ENERGY CORPORATION

                            -----------------------
                                   PROSPECTUS
                            -----------------------

                                           , 2000

- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
<PAGE>   50

                                    PART II

                     INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 20. INDEMNIFICATION OF DIRECTORS AND OFFICERS.

     Pursuant to the provisions of the Wisconsin Business Corporation Law and
Article VIII of the Registrants' Bylaws, directors and officers of the
Registrants are entitled to mandatory indemnification from the Registrants
against certain liabilities (which may include liabilities under the Securities
Act of 1933) and expenses (i) to the extent such officers or directors are
successful in the defense of a proceeding; and (ii) in proceedings in which the
director or officer is not successful in defense thereof, unless it is
determined that the director or officer breached or failed to perform his or her
duties to either Registrant and such breach or failure constituted: (a) a
willful failure to deal fairly with either Registrant or its shareholders in
connection with a matter in which the director or officer had a material
conflict of interest; (b) a violation of criminal law unless the director or
officer had a reasonable cause to believe his or her conduct was lawful or had
no reasonable cause to believe his or her conduct was unlawful; (c) a
transaction from which the director or officer derived an improper personal
profit; or (d) willful misconduct. Additionally, under the Wisconsin Business
Corporation Law, directors of the Registrants are not subject to personal
liability to the Registrants, their shareholders or any person asserting rights
on behalf thereof, for certain breaches or failures to perform any duty
resulting solely from their status as directors, except in circumstances
paralleling those outlined in (a) through (d) above.

     The indemnification provided by the Wisconsin Business Corporation Law and
the Registrants' Bylaws is not exclusive of any other rights to which a director
or officer of the Registrants may be entitled. The Registrants also carry
directors' and officers' liability insurance.

     The Registration Rights Agreement contains provisions under which the
underwriters agree to indemnify the directors and officers of the Registrants
against certain liabilities, including liabilities under the Securities Act of
1933 or to contribute to payments the directors and officers may be required to
make in respect thereof.

ITEM 21. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES.

     (a) Exhibits. The exhibits listed in the accompanying Exhibit Index are
filed (except where otherwise indicated) as part of this Joint Registration
Statement.

     (b) Financial Statement Schedules. Schedule II - Valuation and Qualifying
Accounts is hereby incorporated by reference to Alliant Energy Corporation's
Annual Report on Form 10-K for the year ended December 31, 1998, as amended
(File No. 1-9894). All other schedules are omitted because they are not
applicable or not require, or because the required information is shown either
in the consolidated financial statements or in the notes thereto.

     (c) Reports, Opinions or Appraisals. Not applicable.

ITEM 22. UNDERTAKINGS.

     (a) The undersigned Registrant hereby undertakes:

          (1) To file, during any period in which offers or sales are being
     made, a post-effective amendment to this Registration Statement:

             (i) To include any prospectus required by Section 10(a)(3) of the
        Securities Act of 1933;

             (ii) To reflect in the prospectus any facts or events arising after
        the effective date of the Registration Statement (or the most recent
        post-effective amendment thereof) which, individually or in the
        aggregate, represent a fundamental change in the information set forth
        in the Registration Statement. Notwithstanding the foregoing, any
        increase or decrease in volume of securities offered (if the total
        dollar value of securities offered would not exceed that which was
        registered) and any deviation from the low or high end of the estimated
        maximum offering range
                                      II-1
<PAGE>   51

        may be reflected in the form of prospectus filed with the Commission
        pursuant to Rule 424(b) if, in the aggregate, the changes in volume and
        price represent no more than a 20% change in the maximum aggregate
        offering price set forth in the "Calculation of Registration Fee" table
        in the effective Registration Statement;

             (iii) To include any material information with respect to the plan
        of distribution not previously disclosed in the Registration Statement
        or any material change to such information in the registration
        statement.

        Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply
        if the Registration Statement is on Form S-3 or Form S-8, and the
        information required to be included in a post-effective amendment by
        those paragraphs is contained in periodic reports filed by the
        Registrant pursuant to Section 13 or Section 15(d) of the Securities
        Exchange Act of 1934 that are incorporated by reference in the
        Registration Statement.

          (2) That, for the purpose of determining any liability under the
     Securities Act of 1933, each such post-effective amendment shall be deemed
     to be a new Registration Statement relating to the securities offered
     therein, and the offering of such securities at that time shall be deemed
     to be the initial bona fide offering thereof.

          (3) To remove from registration by means of a post-effective amendment
     any of the securities being registered which remain unsold at the
     termination of the offering.

     (b) Each of the undersigned Registrants hereby undertakes that, for
purposes of determining any liability under the Securities Act of 1933, each
filing of the Registrant's annual report pursuant to Section 13(a) or Section
15(d) of the Securities Exchange Act of 1934 that is incorporated by reference
in the Registration Statement shall be deemed to be a new Registration Statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

     (c) Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to directors, officers and controlling persons of
the Registrants pursuant to the foregoing provisions, or otherwise, the
Registrants have been advised that in the opinion of the Securities and Exchange
Commission such indemnification is against public policy as expressed in the
Securities Act of 1933 and is, therefore, unenforceable. In the event that a
claim for indemnification against such liabilities (other than the payment by a
Registrant of expenses incurred or paid by a director, officer or controlling
person of a Registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, each of the Registrants will,
unless in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the Act and
will be governed by the final adjudication of such issue.

     (d) Each of the undersigned Registrants hereby undertakes to respond to
requests for information that is incorporated by reference into the Prospectus
pursuant to Item 4, 10(b), 11 or 13 of this form, within one business day of
receipt of such request, and to send the incorporated documents by first class
mail or other equally prompt means. This includes information contained in
documents filed subsequent to the effective date of the Registration Statement
through the date of responding to the request.

     (e) Each of the undersigned Registrants hereby undertakes to supply by
means of a post-effective amendment all information concerning a transaction,
and the company being acquired involved therein, that was not the subject of and
included in the Registration Statement when it became effective.

                                      II-2
<PAGE>   52

                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant
has duly caused this Amendment to the Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized, in the City of Madison,
State of Wisconsin, on April 25, 2000.


                                          ALLIANT ENERGY RESOURCES, INC.

                                          By:   /s/ ERROLL B. DAVIS, JR.
                                            ------------------------------------
                                                    Erroll B. Davis, Jr.
                                                  Chief Executive Officer

     Pursuant to the requirements of the Securities Act of 1933, this Amendment
to the Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.


<TABLE>
<CAPTION>
                  SIGNATURE                                       TITLE                          DATE
                  ---------                                       -----                          ----
<C>                                              <S>                                        <C>
          /s/ ERROLL B. DAVIS, JR.               Chief Executive Officer and Director       April 25, 2000
- ---------------------------------------------    (Principal Executive Officer)
            Erroll B. Davis, Jr.

            /s/ EDWARD M. GLEASON                Vice President-Treasurer and Corporate     April 25, 2000
- ---------------------------------------------    Secretary (Principal Financial Officer)
              Edward M. Gleason

             /s/ DANIEL A. DOYLE                 Vice President, Chief Accounting and       April 25, 2000
- ---------------------------------------------    Financial Planning Officer
               Daniel A. Doyle                   (Principal Accounting Officer)

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Alan B. Arends

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                Jack B. Evans

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Rockne G. Flowers

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Joyce L. Hanes

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                   Lee Liu

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
             Katharine C. Lyall

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Arnold M. Nemirow

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Milton E. Neshek
</TABLE>


                                      II-3
<PAGE>   53


<TABLE>
<CAPTION>
                  SIGNATURE                                       TITLE                          DATE
                  ---------                                       -----                          ----
<C>                                              <S>                                        <C>
                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Judith D. Pyle

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                Robert D. Ray

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Robert W. Schlutz

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
            Wayne H. Stoppelmoor

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Anthony R. Weiler

         *By: /s/ EDWARD M. GLEASON
   ---------------------------------------
              Edward M. Gleason
              Attorney-in-fact
</TABLE>


                                      II-4
<PAGE>   54

                                   SIGNATURES


     Pursuant to the requirements of the Securities Act of 1933, the Registrant
has duly caused this Amendment to the Registration Statement to be signed on its
behalf by the undersigned, thereunto duly authorized, in the City of Madison,
State of Wisconsin, on April 25, 2000.


                                          ALLIANT ENERGY CORPORATION

                                          By:   /s/ ERROLL B. DAVIS, JR.
                                            ------------------------------------
                                                    Erroll B. Davis, Jr.
                                               President and Chief Executive
                                                           Officer

     Pursuant to the requirements of the Securities Act of 1933, this Amendment
to the Registration Statement has been signed by the following persons in the
capacities and on the dates indicated.


<TABLE>
<CAPTION>
                  SIGNATURE                                       TITLE                          DATE
                  ---------                                       -----                          ----
<C>                                              <S>                                        <C>
          /s/ ERROLL B. DAVIS, JR.               President and Chief Executive Officer      April 25, 2000
- ---------------------------------------------    and Director (Principal Executive
            Erroll B. Davis, Jr.                 Officer)

            /s/ THOMAS M. WALKER                 Executive Vice President and Chief         April 25, 2000
- ---------------------------------------------    Financial Officer (Principal Financial
              Thomas M. Walker                   Officer)

             /s/ DANIEL A. DOYLE                 Vice President, Chief Accounting and       April 25, 2000
- ---------------------------------------------    Financial Planning Officer
               Daniel A. Doyle                   (Principal Accounting Officer)

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Alan B. Arends

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                Jack B. Evans

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Rockne G. Flowers

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Joyce L. Hanes

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                   Lee Liu

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
             Katharine C. Lyall

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Arnold M. Nemirow

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Milton E. Neshek
</TABLE>


                                      II-5
<PAGE>   55


<TABLE>
<CAPTION>
                  SIGNATURE                                       TITLE                          DATE
                  ---------                                       -----                          ----
<C>                                              <S>                                        <C>
                      *                          Director                                   April 25, 2000
- ---------------------------------------------
               Judith D. Pyle

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
                Robert D. Ray

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Robert W. Schlutz

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
            Wayne H. Stoppelmoor

                      *                          Director                                   April 25, 2000
- ---------------------------------------------
              Anthony R. Weiler

         *By: /s/ EDWARD M. GLEASON
   ---------------------------------------
              Edward M. Gleason
              Attorney-in-fact
</TABLE>


                                      II-6
<PAGE>   56

                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
NUMBER                         DOCUMENT DESCRIPTION
- -------                        --------------------
<S>        <C>
 (4.1)     Indenture, dated as of November 4, 1999, among Alliant
           Energy Resources, Inc., Alliant Energy Corporation, as
           Guarantor, and Firstar Bank, N.A., as Trustee.*
 (4.2)     First Supplemental Indenture, dated as of November 4, 1999,
           among Alliant Energy Resources, Inc., Alliant Energy
           Corporation, as Guarantor, and Firstar Bank, N.A., as
           Trustee.*
 (4.3)     Form of New 7 3/8% Senior Notes due 2009 and related
           Guarantees.*
 (4.4)     Purchase Agreement, dated as of November 4, 1999, among
           Alliant Energy Resources, Inc., Alliant Energy Corporation,
           Merrill Lynch, Pierce, Fenner & Smith Incorporated, Morgan
           Stanley & Co. Incorporated, Salomon Smith Barney Inc., ABN
           AMRO Incorporated and Barclays Capital Inc.*
 (4.5)     Registration Rights Agreement, dated as of November 9, 1999,
           among Alliant Energy Resources, Inc., Alliant Energy
           Corporation, Merrill Lynch, Pierce, Fenner & Smith
           Incorporated, Morgan Stanley & Co. Incorporated, Salomon
           Smith Barney Inc., ABN AMRO Incorporated and Barclays
           Capital Inc.*
 (4.6)     Indenture of Mortgage or Deed of Trust dated August 1, 1941,
           between Wisconsin Power and Light Company ("WP&L") and First
           Wisconsin Trust Company (n/k/a Firstar Bank, N.A.) and
           George B. Luhman, as Trustees, filed as Exhibit 7(a) in File
           No. 2-6409, and the indentures supplemental thereto dated,
           respectively, January 1, 1948, September 1, 1948, June 1,
           1950, April 1, 1951, April 1, 1952, September 1, 1953,
           October 1, 1954, March 1, 1959, May 1, 1962, August 1, 1968,
           June 1, 1969, October 1, 1970, July 1, 1971, April 1, 1974,
           December 1, 1975, May 1, 1976, May 15, 1978, August 1, 1980,
           January 15, 1981, August 1, 1984, January 15, 1986, June 1,
           1986, August 1, 1988, December 1, 1990, September 1, 1991,
           October 1, 1991, March 1, 1992, May 1, 1992, June 1, 1992
           and July 1, 1992 (Second Amended Exhibit 7(b) in File No.
           2-7361; Amended Exhibit 7(c) in File No. 2-7628; Amended
           Exhibit 7.02 in File No. 2-8462; Amended Exhibit 7.02 in
           File No. 2-8882; Second Amendment Exhibit 4.03 in File No.
           2-9526; Amended Exhibit 4.03 in File No. 2-10406; Amended
           Exhibit 2.02 in File No. 2-11130; Amended Exhibit 2.02 in
           File No. 2-14816; Amended Exhibit 2.02 in File No. 2-20372;
           Amended Exhibit 2.02 in File No. 2-29738; Amended Exhibit
           2.02 in File No. 2-32947; Amended Exhibit 2.02 in File No.
           2-38304; Amended Exhibit 2.02 in File No. 2-40802; Amended
           Exhibit 2.02 in File No. 2-50308; Exhibit 2.01(a) in File
           No. 2-57775; Amended Exhibit 2.02 in File No. 2-56036;
           Amended Exhibit 2.02 in File No. 2-61439; Exhibit 4.02 in
           File No. 2-70534; Amended Exhibit 4.03 File No. 2-70534;
           Exhibit 4.02 in File No. 33-2579; Amended Exhibit 4.03 in
           File No. 33-2579; Amended Exhibit 4.02 in File No. 33-4961;
           Exhibit 4B to WP&L's Form 10-K for the year ended December
           31, 1988, Exhibit 4.1 to WP&L's Form 8-K dated December 10,
           1990, Amended Exhibit 4.26 in File No. 33-45726, Amended
           Exhibit 4.27 in File No.33-45726, Exhibit 4.1 to WP&L's Form
           8-K dated March 9, 1992, Exhibit 4.1 to WP&L's Form 8-K
           dated May 12, 1992, Exhibit 4.1 to WP&L's Form 8-K dated
           June 29, 1992 and Exhibit 4.1 to WP&L's Form 8-K dated July
           20, 1992).
 (4.7)     Indenture, dated as of June 20, 1997, between WP&L and
           Firstar Trust Company (n/k/a Firstar Bank, N.A.), as
           Trustee, relating to debt securities (incorporated by
           reference to Exhibit 4.33 to Amendment No. 2 to WP&L's
           Registration Statement on Form S-3 (Registration No.
           33-60917)).
 (4.8)     Officers' Certificate, dated as of June 25, 1997, creating
           WP&L's 7% debentures due June 15, 2007 (incorporated by
           reference to Exhibit 4 to WP&L's Current Report on Form 8-K,
           dated June 25, 1997).
 (4.9)     Officers' Certificate, dated as of October 27, 1998,
           creating WP&L's 5.70% debentures due October 15, 2008
           (incorporated by reference to Exhibit 4 to WP&L's Current
           Report on Form 8-K, dated October 27, 1998).
</TABLE>

                                       E-1
<PAGE>   57

<TABLE>
<CAPTION>
EXHIBIT
NUMBER                         DOCUMENT DESCRIPTION
- -------                        --------------------
<S>        <C>
 (4.10)    Officers' Certificate, dated as of March 1, 2000, creating
           WP&L's 7 5/8% debentures due March 1, 2010 (incorporated by
           reference to Exhibit 4 to WP&L's Current Report on Form 8-K,
           dated March 1, 2000).
 (4.11)    Indenture of Mortgage and Deed of Trust, dated as of
           September 1, 1993, between IES Utilities Inc. ("IESU")
           (formerly Iowa Electric Light and Power Company ("IE")) and
           The First National Bank of Chicago, as Trustee ("Mortgage")
           (incorporated by reference to Exhibit 4(c) to IESU's Form
           10-Q for the quarter ended September 30, 1993).
 (4.12)    Supplemental Indentures to IESU's 1993 Mortgage:
</TABLE>

<TABLE>
<CAPTION>
                                                                          IESU/IES INDUSTRIES INC
                          NUMBER                       DATED AS OF            FILE REFERENCE          EXHIBIT
                          ------                       -----------        -----------------------     -------
           <S>                                      <C>                  <C>                          <C>
           First................................    October 1, 1993      Form 10-Q, 11/12/93          4   (d)
           Second...............................    November 1, 1993     Form 10-Q, 11/12/93          4   (e)
           Third................................    March 1, 1995        Form 10-Q, 5/12/95           4   (b)
           Fourth...............................    September 1, 1996    Form 8-K, 9/19/96            4   (c)(i)
           Fifth................................    April 1, 1997        Form 10-Q, 5/14/97           4   (a)
</TABLE>

<TABLE>
<S>        <C>
 (4.13)    Indenture of Mortgage and Deed of Trust, dated as of August
           1, 1940, between IESU (formerly IE) and The First National
           Bank of Chicago, Trustee ("1940 Indenture") (incorporated by
           reference to Exhibit 2(a) to IESU's Registration Statement,
           File No. 2-25347).
 (4.14)    Supplemental Indentures to IESU's 1940 Indenture:
</TABLE>

<TABLE>
<CAPTION>
                                                                               IESU
                         NUMBER                      DATED AS OF          FILE REFERENCE       EXHIBIT
                         ------                      -----------          --------------       -------
<S>       <C>                                     <C>                   <C>                    <C>
          First...............................    March 1, 1941         2-25347                2(a)
          Second..............................    July 15, 1942         2-25347                2(a)
          Third...............................    August 2, 1943        2-25347                2(a)
          Fourth..............................    August 10, 1944       2-25347                2(a)
          Fifth...............................    November 10, 1944     2-25347                2(a)
          Sixth...............................    August 8, 1945        2-25347                2(a)
          Seventh.............................    July 1, 1946          2-25347                2(a)
          Eighth..............................    July 1, 1947          2-25347                2(a)
          Ninth...............................    December 15, 1948     2-25347                2(a)
          Tenth...............................    November 1, 1949      2-25347                2(a)
          Eleventh............................    November 10, 1950     2-25347                2(a)
          Twelfth.............................    October 1, 1951       2-25347                2(a)
          Thirteenth..........................    March 1, 1952         2-25347                2(a)
          Fourteenth..........................    November 5, 1952      2-25347                2(a)
          Fifteenth...........................    February 1, 1953      2-25347                2(a)
          Sixteenth...........................    May 1, 1953           2-25347                2(a)
          Seventeenth.........................    November 3, 1953      2-25347                2(a)
          Eighteenth..........................    November 8, 1954      2-25347                2(a)
          Nineteenth..........................    January 1, 1955       2-25347                2(a)
          Twentieth...........................    November 1, 1955      2-25347                2(a)
          Twenty-first........................    November 9, 1956      2-25347                2(a)
          Twenty-second.......................    November 6, 1957      2-25347                2(a)
          Twenty-third........................    November 4, 1958      2-25347                2(a)
          Twenty-fourth.......................    November 3, 1959      2-25347                2(a)
          Twenty-fifth........................    November 1, 1960      2-25347                2(a)
          Twenty-sixth........................    January 1, 1961       2-25347                2(a)
</TABLE>

                                       E-2
<PAGE>   58

<TABLE>
<CAPTION>
                                                 DOCUMENT DESCRIPTION
                                                 --------------------
EXHIBIT                                                                  IESU/IES INDUSTRIES INC
NUMBER                    NUMBER                      DATED AS OF            FILE REFERENCE         EXHIBIT
- -------                   ------                      -----------        -----------------------    -------
<S>        <C>                                     <C>                   <C>                        <C>
           Twenty-seventh......................    November 7, 1961      2-25347                    2(a)
           Twenty-eighth.......................    November 6, 1962      2-25347                    2(a)
           Twenty-ninth........................    November 5, 1963      2-25347                    2(a)
           Thirtieth...........................    November 4, 1964      2-25347                    2(a)
           Thirty-first........................    November 2, 1965      2-25347                    2(a)
           Thirty-second.......................    September 1, 1966     Form 10-K, 1966            4.10
           Thirty-third........................    November 30, 1966     Form 10-K, 1966            4.10
           Thirty-fourth.......................    November 7, 1967      Form 10-K, 1967            4.10
           Thirty-fifth........................    November 5, 1968      Form 10-K, 1968            4.10
           Thirty-sixth........................    November 1, 1969      Form 10-K, 1969            4.10
           Thirty-seventh......................    December 1, 1970      Form 8-K, 12/70            1
           Thirty-eighth.......................    November 2, 1971      2-43131                    2(g)
           Thirty-ninth........................    May 1, 1972           Form 8-K, 5/72             1
           Fortieth............................    November 7, 1972      2-56078                    2(i)
           Forty-first.........................    November 7, 1973      2-56078                    2(j)
           Forty-second........................    September 10, 1974    2-56078                    2(k)
           Forty-third.........................    November 5, 1975      2-56078                    2(l)
           Forty-fourth........................    July 1, 1976          Form 8-K, 7/76             1
           Forty-fifth.........................    November 1, 1976      Form 8-K, 12/76            1
           Forty-sixth.........................    December 1, 1977      2-60040                    2(o)
           Forty-seventh.......................    November 1, 1978      Form 10-Q, 6/30/79         1
           Forty-eighth........................    December 1, 1979      Form S-16, 2-65996         2(q)
           Forty-ninth.........................    November 1, 1981      Form 10-Q, 3/31/82         2
           Fiftieth............................    December 1, 1980      Form 10-K, 1981            4(s)
           Fifty-first.........................    December 1, 1982      Form 10-K, 1982            4(t)
           Fifty-second........................    December 1, 1983      Form 10-K, 1983            4(u)
           Fifty-third.........................    December 1, 1984      Form 10-K, 1984            4(v)
           Fifty-fourth........................    March 1, 1985         Form 10-K, 1984            4(w)
           Fifty-fifth.........................    March 1, 1988         Form 10-Q, 5/12/88         4(b)
           Fifty-sixth.........................    October 1, 1988       Form 10-Q, 11/10/88        4(c)
           Fifty-seventh.......................    May 1, 1991           Form 10-Q, 8/13/91         4(d)
           Fifty-eighth........................    March 1, 1992         Form 10-K, 1991            4(c)
           Fifty-ninth.........................    October 1, 1993       Form 10-Q, 11/12/93        4(a)
           Sixtieth............................    November 1, 1993      Form 10-Q, 11/12/93        4(b)
           Sixty-first.........................    March 1, 1995         Form 10-Q, 5/12/95         4(a)
           Sixty-second........................    September 1, 1996     Form 8-K, 9/19/96          4(f)
           Sixty-third.........................    April 1, 1997         Form 10-Q, 5/14/97         4(b)
</TABLE>

<TABLE>
<S>       <C>
          Indenture or Deed of Trust dated as of February 1, 1923,
(4.15)    between IESU (successor to Iowa Southern Utilities Company
          ("IS") as result of merger of IS and IE) and The Northern
          Trust Company (The First National Bank of Chicago,
          successor) and Harold H. Rockwell (Richard D. Manella,
          successor), as Trustees (1923 Indenture) (incorporated by
          reference to Exhibit B-1 to File No. 2-1719).
          Supplemental Indentures to IESU's 1923 Indenture:
(4.16)
</TABLE>

<TABLE>
<CAPTION>
                                  DATED AS OF                             FILE REFERENCE    EXHIBIT
                                  -----------                             --------------    -------
<S>       <C>                                                             <C>               <C>
          May 1, 1940.................................................    2-4921            B-1-k
          May 2, 1940.................................................    2-4921            B-1-l
          October 1, 1945.............................................    2-8053            7(m)
</TABLE>

                                       E-3
<PAGE>   59

<TABLE>
<CAPTION>
                                             DOCUMENT DESCRIPTION
EXHIBIT                                      --------------------
NUMBER                             DATED AS OF                             FILE REFERENCE    EXHIBIT
- -------                            -----------                             --------------    -------
<S>        <C>                                                             <C>               <C>
           October 2, 1945.............................................    2-8053            7(n)
           January 1, 1948.............................................    2-8053            7(o)
           September 1, 1950...........................................    33-3995           4(e)
           February 1, 1953............................................    2-10543           4(b)
           October 2, 1953.............................................    2-10543           4(q)
           August 1, 1957..............................................    2-13496           2(b)
           September 1, 1962...........................................    2-20667           2(b)
           June 1, 1967................................................    2-26478           2(b)
           February 1, 1973............................................    2-46530           2(b)
           February 1, 1975............................................    2-53860           2(aa)
           July 1, 1975................................................    2-54285           2(bb)
           September 2, 1975...........................................    2-57510           2(bb)
           March 10, 1976..............................................    2-57510           2(cc)
           February 1, 1977............................................    2-60276           2(ee)
           January 1, 1978.............................................    0-849             2
           March 1, 1979...............................................    0-849             2
           March 1, 1980...............................................    0-849             2
           May 31, 1986................................................    33-3995           4(g)
           July 1, 1991................................................    0-849             4(h)
           September 1, 1992...........................................    0-849             4(m)
           December 1, 1994............................................    0-4117-1          4(f)
</TABLE>

<TABLE>
<S>       <C>
          Indenture (For Unsecured Subordinated Debt Securities),
(4.17)    dated as of December 1, 1995, between IESU and The First
          National Bank of Chicago, as Trustee (Subordinated
          Indenture) (incorporated by reference to Exhibit 4(i) to
          IESU's Amendment No. 1 to Registration Statement, File No.
          33-62259).
          Indenture (For Senior Unsecured Debt Securities), dated as
(4.18)    of August 1, 1997, between IESU and The First National Bank
          of Chicago, as Trustee (incorporated by reference to Exhibit
          4(j) to IESU's Registration Statement, File No. 333-32097).
          The Original through the Nineteenth Supplemental Indentures
(4.19)    of Interstate Power Company ("IPC") to The Chase Manhattan
          Bank and Carl E. Buckley and C. J. Heinzelmann, as Trustees,
          dated January 1, 1948 securing First Mortgage Bonds
          (incorporated by reference to Exhibits 4(b) through 4(t) to
          IPC's Registration Statement No. 33-59352 dated March 11,
          1993).
          Twentieth Supplemental Indenture of IPC to The Chase
(4.20)    Manhattan Bank and C. J. Heinzelmann, as Trustees, dated May
          15, 1993 (incorporated by reference to Exhibit 4(u) to IPC's
          Registration Statement No. 33-59352 dated March 11, 1993).
          Second Supplemental Indenture, dated as of February 1, 2000,
(4.21)    among Alliant Energy Resources, Inc., Alliant Energy
          Corporation, as Guarantor, and Firstar Bank, N.A., as
          Trustee (incorporated by reference to Exhibit 99.4 to
          Alliant Energy Corporation's Current Report on Form 8-K
          dated February 1, 2000).
          Purchase Agreement, dated as of January 26, 1999, among
(4.22)    Alliant Energy Resources, Inc., Alliant Energy Corporation
          and Merrill Lynch, Pierce, Fenner & Smith Incorporated
          (incorporated by reference to Exhibit 99.2 to Alliant Energy
          Corporation's Current Report on Form 8-K dated February 1,
          2000).
          Registration Rights Agreement, dated as of February 1, 2000,
(4.23)    among Alliant Energy Resources, Inc., Alliant Energy
          Corporation and Merrill Lynch, Pierce, Fenner & Smith
          Incorporated (incorporated by reference to Exhibit 99.5 to
          Alliant Energy Corporation's Current Report on Form 8-K
          dated February 1, 2000).
</TABLE>

                                       E-4
<PAGE>   60

<TABLE>
<S>       <C>
          Pursuant to Item 601(b)(4)(iii) of Regulation S-K, the
          registrants agree to furnish to the Securities and Exchange
          Commission, upon request, any instrument defining the rights
          of holders of long-term debt not being registered that is
          not filed as an exhibit to this Registration Statement on
          Form S-4. No such instrument authorizes securities in excess
          of 10% of the total assets of Alliant Energy Corporation or
          Alliant Energy Resources, Inc., as the case may be.
 (5)      Opinion of Foley & Lardner (including consent of counsel).*
(12)      Statement re computation of ratios of earnings to fixed
          charges.*
(23.1)    Consent of Arthur Andersen LLP
(23.2)    Consent of Foley & Lardner (filed as part of Exhibit (5)).*
(24)      Powers of attorney.*
(25)      Form T-1 Statement of Eligibility and Qualification under
          the Trust Indenture Act of 1939 of Firstar Bank, N.A.*
(99.1)    Form of Letter of Transmittal.*
(99.2)    Form of Notice of Guaranteed Delivery.*
(99.3)    Guidelines for Certification of Taxpayer Identification
          Number on Substitute Form W-9.*
(99.4)    Form of Letter to Clients.*
(99.5)    Form of Instructions to Registered Holder and/or DTC
          Participant from Beneficial Owners.*
(99.6)    Form of Letter to Nominees.*
</TABLE>


- ---------------
 * Previously filed

     Documents incorporated by reference to filings made by Alliant Energy
Corporation under the Securities Exchange Act of 1934, as amended, are under
File No. 1-9894. Documents incorporated by reference to filings made by
Wisconsin Power and Light Company under the Securities Exchange Act of 1934, as
amended, are under File No. 0-337. Documents incorporated by reference to
filings made by IES Industries Inc. under the Securities Exchange Act of 1934,
as amended, are under File No. 1-9187. Documents incorporated by reference to
filings made by IES Utilities Inc. under the Securities Exchange Act of 1934, as
amended, are under File No. 0-4117-1. Documents incorporated by reference to
filings made by Interstate Power Company under the Securities Exchange Act of
1934, as amended, are under File No. 1-3632.

                                       E-5

<PAGE>   1

CONSENT OF INDEPENDENT PUBLIC ACCOUNTANTS



As independent public accountants, we hereby consent to the incorporation by
reference in this registration statement of our report dated January 28, 2000 on
the consolidated financial statements of Alliant Energy Corporation included in
Alliant Energy Corporation's Annual Report on Form 10-K for the year ended
December 31, 1999, and to all references to our Firm included in this
registration statement.



/s/  Arthur Andersen LLP
ARTHUR ANDERSEN LLP


Milwaukee, Wisconsin
April 25, 2000


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