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                              ARTICLES OF AMENDMENT
                                       OF
                       INTERSTATE POWER AND LIGHT COMPANY

           (Regarding Designation and Authorization of 7.10% Series C
                           Cumulative Preferred Stock)

TO THE SECRETARY OF STATE
OF THE STATE OF IOWA:

          Pursuant to Section 490.602 of the Iowa Business Corporation Act,
Interstate Power and Light Company, an Iowa corporation (the "Corporation"),
adopts the following amendment regarding the designation and authorization of
7.10% Series C Cumulative Preferred Stock by the Corporation.

1.   The name of the Corporation is Interstate Power and Light Company.

2.   The preferences, limitations, relative rights and other terms of the 7.10%
     Series C Cumulative Preferred Stock were determined by an ad hoc special
     committee of the Corporation's Board of Directors, consisting of Erroll B.
     Davis, Jr. (the "Committee"), pursuant to authority granted by the Board of
     Directors of the Corporation under Section 490.825 of the Iowa Business
     Corporation Act on August 20, 2003. A true and correct copy of the portion
     of the consent action by which the Committee authorized the 7.10% Series C
     Cumulative Preferred Stock and determined the preferences, limitations,
     relative rights and other terms thereof is attached hereto as Exhibit A and
     incorporated herein by this reference.

3.   The consent action of the Committee as set forth in Exhibit A was duly
     adopted by the Committee on September 9, 2003 pursuant to authority granted
     by the Board of Directors of the Corporation under Section 490.825 of the
     Iowa Business Corporation Act on August 20, 2003.

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Dated:  September 9, 2003

                                                  INTERSTATE POWER AND
                                                  LIGHT COMPANY


                                                  By: /s/ F.J. Buri
                                                     ---------------------------
                                                     F.J. Buri
                                                     Corporate Secretary

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                 CONSENT ACTION OF THE AD HOC SPECIAL COMMITTEE
                     OF THE BOARD OF DIRECTORS ESTABLISHING
                    7.10% SERIES C CUMULATIVE PREFERRED STOCK

          There is hereby authorized and established a series of shares of
Preferred Stock, $.01 par value, of the Corporation to be known and designated
as the 7.10% Series C Cumulative Preferred Stock, with the preferences,
limitations, relative rights and other terms as set forth below.

                           CERTIFICATE OF DESIGNATION

                    7.10% Series C Cumulative Preferred Stock

     Section 1. Designation and Number.

          (a) There is hereby created out of the authorized but unissued
Preferred Stock a series of Preferred Stock designated as "7.10% Series C
Cumulative Preferred Stock" (the "Series C Preferred Stock"). The number of
shares constituting the Series C Preferred Stock shall be 1,600,000.

          (b) All shares of the Series C Preferred Stock redeemed, purchased,
exchanged, converted or otherwise acquired by the Corporation shall be retired
and canceled and, upon the taking of any action required by applicable law,
shall be restored to the status of authorized but unissued shares of Preferred
Stock, without designation as to series, and may thereafter be designated or
redesignated and issued or reissued as part of any series of Preferred Stock.

          (c) Capitalized terms used herein and not otherwise defined herein or
in the Corporation's Restated Articles of Incorporation shall have the meanings
set forth in Section 7.

     Section 2. Ranking.

          (a) The Series C Preferred Stock shall rank, with respect to payment
of dividends and distribution of assets upon liquidation, dissolution or winding
up of the Corporation:

               (i)  senior to Junior Stock; and

               (ii) on a parity with Parity Stock.

     Section 3. Dividends.

          (a) The holders of shares of the Series C Preferred Stock shall be
entitled to receive, when, as and if declared by the Board of Directors out of
funds legally available for the payment of dividends, per share cash dividends
at an annual rate of 7.10% of the Liquidation Preference.

          (b) All dividends on the Series C Preferred Stock shall accrue and be
cumulative from the date of original issuance. Dividends shall be payable
quarterly in arrears on March 15, June 15, September 15 and December 15 of each
year, beginning on December 15, 2003. If any

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of those dates is not a Business Day, then dividends shall be payable on the
next succeeding Business Day. Dividends shall be payable on those dates to
holders of record as they appear in the stock records of the Corporation at the
close of business on the applicable record date, which shall be the last
Business Day of the month prior to the month in which the applicable dividend
payment date falls. The amount of dividends payable for the initial dividend
period or any period shorter than a full dividend period shall be computed on
the basis of a 360-day year consisting of twelve 30-day months and the actual
number of days elapsed in the period.

          (c) The Board of Directors shall not authorize, and the Corporation
shall not pay, any dividends on the Series C Preferred Stock or set aside funds
for the payment of dividends if the terms of any of the Corporation's
agreements, including agreements relating to indebtedness, prohibit that
authorization, payment or setting aside of funds or provide that the
authorization, payment or setting aside of funds is a breach of or a default
under that agreement, or if the authorization, payment or setting aside of funds
is restricted or prohibited by law.

          (d) Notwithstanding the provisions of Section 3(c), dividends on the
Series C Preferred Stock shall accrue whether or not the Corporation has
earnings, whether or not there are funds legally available for the payment of
dividends and whether or not dividends are authorized. No interest shall be paid
in respect of any accrued but unpaid dividends on the Series C Preferred Stock.

          (e) Holders of shares of the Series C Preferred Stock shall not be
entitled to any dividends in excess of full cumulative dividends on the Series C
Preferred Stock as described above. Any dividend payment made on the Series C
Preferred Stock shall first be credited against the earliest accrued and unpaid
dividend due.

          (f) The Corporation shall not pay any dividends with respect to Junior
Stock if dividends payable on the Series C Preferred Stock are in arrears.

     Section 4. Liquidation Preference.

          (a) Upon any voluntary or involuntary liquidation, dissolution or
winding up of the Corporation, each holder of shares of the Series C Preferred
Stock shall be entitled to payment, out of the Corporation's assets available
for distribution to its shareowners, of an amount equal to the Liquidation
Preference plus an amount equal to all accrued and unpaid dividends on those
shares to, but excluding, the date of liquidation, dissolution or winding up
before any distribution is made on any Junior Stock. After payment in full of
the Liquidation Preference and the amount equal to all accrued and unpaid
dividends to which holders of shares of the Series C Preferred Stock are
entitled, the holders of the Series C Preferred Stock shall not be entitled to
any further participation in any distribution of the Corporation's assets. If
upon any voluntary or involuntary liquidation, dissolution or winding up of the
Corporation, the amounts payable with respect to shares of the Series C
Preferred Stock and any Parity Stock are not paid in full, then the holders of
shares of the Series C Preferred Stock and the holders of the Parity Stock shall
share equally and ratably in any distribution of the Corporation's assets in
proportion to the full distributable amounts to which each such holder is
entitled.

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          (b) Neither the voluntary sale, conveyance, exchange or transfer, for
cash, shares of stock, securities or other consideration, of all or
substantially all of the Corporation's property or assets nor the consolidation,
merger or amalgamation of the Corporation with or into any other entity or the
consolidation, merger or amalgamation of any other entity with or into the
Corporation will be deemed to be a voluntary or involuntary liquidation,
dissolution or winding up of the Corporation.

     Section 5. Redemption.

          (a) The Corporation may not redeem the Series C Preferred Stock prior
to September 15, 2008. On or after September 15, 2008, the Corporation, at its
sole option, may redeem the Series C Preferred Stock, out of funds legally
available therefor, in whole or in part from time to time at a price of $25 per
share, plus an amount equal to accrued and unpaid dividends to, but excluding,
the redemption date (the "Redemption Price").

          (b) In the case of any partial redemption, the Corporation may select
the shares of the Series C Preferred Stock to be redeemed on a pro rata basis,
by lot or any other method that the Corporation, in its discretion, deems fair
and appropriate. However, the Corporation may, without regard to proportionality
or any other factor, redeem all of the shares of the Series C Preferred Stock
held by any holders of fewer than 100 shares of the Series C Preferred Stock (or
all the shares of the Series C Preferred Stock held by holders who would hold
fewer than 100 shares of the Series C Preferred Stock as a result of such
partial redemption).

          (c) If the Corporation elects to redeem the Series C Preferred Stock
in the manner described in this Section 5, then notice of such redemption (the
"Redemption Notice") shall be given to the holders of record of shares of the
Series C Preferred Stock not less than 45 nor more than 90 days before the date
of the redemption (the "Redemption Date"); provided, however, that no failure to
give such Redemption Notice or any deficiency therein shall affect the validity
of the procedure for the redemption of any shares of the Series C Preferred
Stock to be redeemed except as to the holder or holders to whom the Corporation
has failed to give said Redemption Notice or except as to the holder or holders
whose Redemption Notice was defective. All such Redemption Notices shall state:

               (i) the Redemption Date;

               (ii) the Redemption Price;

               (iii) the total number of shares of the Series C Preferred Stock
to be redeemed;

               (iv) that the Redemption Price will become due and payable on the
Redemption Date upon each such share of Series C Preferred Stock to be redeemed
and that dividends thereon will cease to accrue on and after the Redemption
Date; and

               (v) the place or places where certificates for the Series C
Preferred Stock are to be surrendered for payment of the Redemption Price.

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          (d) Prior to any Redemption Date, the Corporation shall deposit with a
designated bank or trust company as paying agent (or, if the Transfer Agent or
the Corporation is acting as the paying agent, segregate and hold in trust) an
amount of consideration sufficient to pay the Redemption Price of all shares of
Series C Preferred Stock which are to be redeemed on that date other than any
Series C Preferred Stock called for redemption prior to the date of such
deposit.

          (e) Notice of redemption having been given as described above, the
Redemption Price of the Series C Preferred Stock to be redeemed shall, on the
Redemption Date, become due and payable, and from and after such date (unless
the Corporation shall default in the payment of the Redemption Price), such
shares of Series C Preferred Stock shall no longer be outstanding, dividends on
such Series C Preferred Stock shall cease to accrue and all rights of holders
thereof as shareowners of the Corporation (except the right to receive the
Redemption Price without interest) shall cease. Upon book-entry transfer or
surrender of any certificate representing any such share of Series C Preferred
Stock for redemption in accordance with said notice, such Redemption Price shall
thereupon be paid.

          (f) If any certificate that represents more than one share of Series C
Preferred Stock, not all of which are subject to redemption, is surrendered at
any office or agency of the Corporation designated for that purpose (with, if
the Corporation or the Transfer Agent so requires, due endorsement by, or a
written instrument of transfer in form satisfactory to the Corporation and the
Transfer Agent duly executed by, the holder thereof or such holder's attorney
duly authorized in writing), the Corporation shall execute, and the Transfer
Agent shall deliver to the holder of such shares of Series C Preferred Stock
without service charge, a new certificate or certificates, representing any
number of shares of Series C Preferred Stock, as requested by such holder, in an
aggregate amount equal to the number of shares not redeemed and represented by
the certificate so surrendered.

          (g) Payment of the Redemption Price for the Series C Preferred Stock
is conditioned upon book-entry transfer or physical delivery of the certificates
representing the Series C Preferred Stock, together with necessary endorsements
to the Transfer Agent at any time after delivery of the Redemption Notice.
Payment of the Redemption Price for the Series C Preferred Stock will be made
promptly following the later of the Redemption Date and the time of book-entry
transfer or physical delivery of the certificates representing the Series C
Preferred Stock subject to redemption.

          (h) If the Transfer Agent holds money sufficient to pay the Redemption
Price of the Series C Preferred Stock on the Redemption Date in accordance with
the terms of this Section 5, then, on the Redemption Date, the Series C
Preferred Stock will cease to be outstanding, whether or not book-entry transfer
is made or certificates representing the Series C Preferred Stock are delivered
to the Transfer Agent. At such time, all rights of a holder as a holder of
Series C Preferred Stock shall terminate, other than the right to receive the
Redemption Price.

          (i) Notwithstanding the foregoing, if the Redemption Date falls after
a dividend payment record date and before the related dividend payment date,
then the holders of the shares of Series C Preferred Stock at the close of
business on that dividend payment record date will be entitled to receive the
dividend payable on those shares on the corresponding dividend payment

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date. However, the Redemption Price payable on such Redemption Date will not
include dividends accruing on that dividend payment record date and payable on
the corresponding dividend payment date.

     Section 6. Voting Rights.

          (a) The shares of Series C Preferred Stock shall have no voting rights
except as set forth in this Section 6 or as otherwise provided by Iowa law.

          (b) In the event that any four quarterly cumulative dividends, whether
consecutive or not, payable on the Series C Preferred Stock are in arrears, the
holders of the Series C Preferred Stock shall have the right, voting separately
as a class together with holders of any Parity Stock upon which like voting
rights have been conferred and are exercisable, at the next meeting of
shareowners called for the election of directors, to elect two members of the
Board of Directors. The right of such holders of the Series C Preferred Stock to
elect members of the Board of Directors shall continue until such time as all
dividends accumulated and in arrears that are payable on such shares of the
Series C Preferred Stock have been paid in full, at which time such right will
terminate, subject to revesting in the event of each and every subsequent
failure to pay dividends as described above. Upon any termination of the right
of the holders of the Series C Preferred Stock to vote as a class for directors,
the term of office of all directors then in office elected by such holders
voting as a class will terminate immediately.

          (c) Without the affirmative vote or consent of the holders of at least
two-thirds of the outstanding shares of the Series C Preferred Stock, voting as
a single class, or voting as a single class together with holders of any other
series of Preferred Stock (i) upon which like voting or consent rights have been
conferred and (ii) which are similarly affected by the matter to be voted upon,
the Corporation shall not:

               (i) increase the amount of authorized shares of the Preferred
Stock or create or issue any class of stock in addition to the Preferred Stock
ranking senior to or on a parity with the Preferred Stock, or any series
thereof, as to the payment of dividends or the distribution of assets;

               (ii) adopt any amendment to the Restated Articles of
Incorporation of the Corporation that adversely alters the preferences, powers
and rights of the Series C Preferred Stock (provided, that Articles of Amendment
to issue a series of Preferred Stock shall not be considered to adversely alter
the preferences, powers and rights of the Series C Preferred Stock solely
because such series is on parity with the Series C Preferred Stock with respect
to payment of dividends and distribution of assets);

               (iii) issue any shares of Preferred Stock of any series if the
cumulative dividends payable on the Series C Preferred Stock are in arrears; or

               (iv) create or issue any shares of Preferred Stock of any series
that rank senior to the Series C Preferred Stock as to payment of dividends or
the distribution of assets.

          (d) On any matter set forth in Section 6(b) or Section 6(c) in which
the holders of the Series C Preferred Stock are entitled to vote as a class,
such holders will be entitled to one

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vote per share. On any other matter for which holders of the Series C Preferred
Stock are provided the right to vote together with holders of the Common Stock
under Iowa law, if any, holders of the Series C Preferred Stock will be entitled
to the number of votes per share determined by dividing the Liquidation
Preference of such share by 100.

     Section 7. Certain Definitions. As used in this Certificate of Designation,
the following terms shall have the following meanings, unless the context
otherwise requires:

          (a) "Board of Directors" means the board of directors of the
Corporation.

          (b) "Business Day" means any day other than a Saturday, Sunday or U.S.
Federal holiday or day on which commercial banks in the City of New York or the
States of Iowa or Wisconsin are authorized or required by law or executive order
to close.

          (c) "Junior Stock" means the Common Stock and any other of the
Corporation's equity securities that by their terms rank junior to the Series C
Preferred Stock with respect to payment of dividends and distribution of assets
upon the liquidation, dissolution or winding up of the Corporation.

          (d) "Liquidation Preference" means $25 per share of the Series C
Preferred Stock.

          (e) "Parity Stock" means the Series B Preferred Stock of the
Corporation and any series of preferred stock established hereafter by the Board
of Directors, the terms of which expressly provide that such series will rank on
a parity with the Series C Preferred Stock with respect to payment of dividends
and distribution of assets upon the liquidation, dissolution or winding up of
the Corporation.

          (f) "Transfer Agent" means the Shareowner Services Department of
Alliant Energy Corporation, as the transfer agent of the Corporation, and any
successor transfer agent duly appointed by the Corporation.

     Section 8. Headings. The headings of the Sections are for convenience of
reference only and shall not define, limit or affect any of the provisions
hereof.

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