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                                                FOLEY & LARDNER
                                                777 East Wisconsin Avenue,
                                                Suite 3800
                                                Milwaukee, Wisconsin  53202-5306
                                                414.271.2400 TEL
                             April 1, 2003      414.297.4900  FAX
                                                www.foleylardner.com


                                                CLIENT/MATTER NUMBER
                                                031613-0139

Alliant Energy Corporation
Alliant Energy Resources, Inc.
4902 North Biltmore Lane
Madison, Wisconsin 53718

Ladies and Gentlemen:

     We have acted as counsel for Alliant Energy Corporation, a Wisconsin
corporation ("Alliant"), and Alliant Energy Resources, Inc., a Wisconsin
corporation ("Resources," and collectively with Alliant, the "Registrants"), in
connection with the preparation of a Registration Statement on Form S-3 (the
"Registration Statement"), including the Prospectus constituting a part thereof
(the "Prospectus"), to be filed with the Securities and Exchange Commission (the
"SEC") under the Securities Act of 1933, as amended (the "Securities Act"),
relating to the issuance and sale by the applicable Registrant from time to time
of up to $400,000,000 aggregate amount of (i) common stock, $.01 par value, of
Alliant (the "Common Stock"), and related Common Share Purchase Rights (the
"Rights") to be issued pursuant to the Rights Agreement, dated January 20, 1999,
by and between Alliant and Wells Fargo Bank Minnesota (the "Rights Agreement");
(ii) senior unsecured debt securities (the "Debt Securities") to be issued under
the Indenture, dated as of November 4, 1999 (the "Indenture"), between
Resources, Alliant and U.S. Bank National Association, as supplemented and
amended; (iii) Alliant's guarantees of the Debt Securities (the "Guarantees") to
be issued under the Indenture; (iv) contracts to purchase shares of Common Stock
(the "Stock Purchase Contracts"); and (v) units, each comprised of a Stock
Purchase Contract and either Debt Securities or debt obligations of third
parties, including U.S. Treasury securities, pledged to secure the holder's
obligation to purchase shares of Common Stock under the Stock Purchase Contracts
(the "Stock Purchase Units"). The Prospectus provides that it will be
supplemented in the future by one or more supplements to such Prospectus (each,
a "Prospectus Supplement").

          As counsel to the Registrants in connection with the proposed issue
and sale of the above-referenced securities, we have examined: (a) the
Registration Statement, including the Prospectus, and the exhibits (including
those incorporated by reference) constituting a part of the Registration
Statement; (b) each Registrant's respective Restated Articles of Incorporation
and Bylaws, each as amended to date; (c) the Rights Agreement; (d) the
Indenture; and (e) such other proceedings, documents and records as we have
deemed necessary to enable us to render this opinion.

          In our examination of the above-referenced documents, we have assumed
the genuineness of all signatures, the authenticity of all documents,
certificates and instruments submitted to us as originals and the conformity
with the originals of all documents submitted to us as copies.


BRUSSELS     DETROIT         MILWAUKEE     SAN DIEGO           TAMPA
CHICAGO      JACKSONVILLE    ORLANDO       SAN DIEGO/DEL MAR   WASHINGTON, D.C.
DENVER       LOS ANGELES     SACRAMENTO    SAN FRANCISCO       WEST PALM BEACH
             MADISON                       TALLAHASSEE




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Alliant Energy Corporation
Alliant Energy Resources, Inc.
April 1, 2003
Page 2


          Based upon the foregoing, we are of the opinion that:

     1. Each Registrant is validly existing as a corporation under the laws of
the State of Wisconsin.

     2. All requisite action necessary to make any shares of Common Stock and
the attached Rights validly issued, fully paid and nonassessable, except with
respect to wage claims of, or other debts owing to, employees of Alliant for
services performed, but not exceeding six months' service in any one case, as
provided in Section 180.0622(2)(b) of the Wisconsin Business Corporation Law
will have been taken when:

          a. An order of the SEC pursuant to the Public Utility Holding Company
     Act of 1935, as amended ("PUHCA"), relating to the issuance of the Common
     Stock and the attached Rights shall be and remain effective and Alliant
     shall have complied with the terms and conditions of such order;

          b. Alliant's Board of Directors, or a duly appointed and authorized
     committee or senior executive officer thereof, shall have adopted
     appropriate resolutions to authorize the issuance and sale of the Common
     Stock and the attached Rights;

          c. Such shares of Common Stock and attached Rights shall have been
     issued and sold for the consideration contemplated by, and otherwise in
     conformity with, the Registration Statement, as supplemented by a
     Prospectus Supplement with respect to such issuance and sale, and the acts,
     proceedings and documents referred to above.

     3. All requisite action necessary to make any Debt Securities valid, legal
and binding obligations of Resources, subject to (i) bankruptcy, insolvency,
reorganization, fraudulent transfer, fraudulent conveyance, moratorium and other
similar laws of general application affecting the rights and remedies of
creditors and (ii) general principles of equity, regardless of whether applied
in a proceeding in equity or at law, shall have been taken when:

          a. The Resources' Board of Directors, or one or more officers duly
     authorized thereby, shall have taken such action to establish the terms of
     such Debt Securities and to authorize the issuance and sale of such Debt
     Securities;

          b. Such Debt Securities shall have been duly executed, authenticated
     and delivered in accordance with the terms and provisions of the Indenture;
     and

          c. Such Debt Securities shall have been issued and sold for the
     consideration contemplated by, and otherwise in conformity with, the
     Registration Statement, as supplemented by a Prospectus Supplement with
     respect to such issuance and sale, and the acts, proceedings and documents
     referred to above.



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Alliant Energy Corporation
Alliant Energy Resources, Inc.
April 1, 2003
Page 3


     4. All requisite action necessary to make any Guarantees valid, legal and
binding obligations of Alliant, subject to (i) bankruptcy, insolvency,
reorganization, fraudulent transfer, fraudulent conveyance, moratorium and other
similar laws of general application affecting the rights and remedies of
creditors and (ii) general principles of equity, regardless of whether applied
in a proceeding in equity or at law, shall have been taken when:

          a. An order of the SEC pursuant to PUHCA relating to the issuance of
     the Guarantees shall be and remain effective and Alliant shall have
     complied with the terms and conditions of such order;

          b. Alliant's Board of Directors, or one or more officers duly
     authorized thereby, shall have taken such action to establish the terms of
     such Guarantees and to authorize the issuance and sale of such Guarantees;

          c. Such Guarantees shall have been duly executed, authenticated and
     delivered in accordance with the terms and provisions of the Indenture; and

          d. Such Guarantees shall have been issued and sold for the
     consideration contemplated by, and otherwise in conformity with, the
     Registration Statement, as supplemented by a Prospectus Supplement with
     respect to such issuance and sale, and the acts, proceedings and documents
     referred to above.

     5. All requisite action necessary to make any Stock Purchase Contracts and
Stock Purchase Units valid, legal and binding obligations of Alliant, subject to
(i) bankruptcy, insolvency, reorganization, fraudulent transfer, fraudulent
conveyance, moratorium and other similar laws of general application affecting
the rights and remedies of creditors and (ii) general principles of equity,
regardless of whether applied in a proceeding in equity or at law, shall have
been taken when:

          a. An order of the SEC pursuant to PUHCA relating to the issuance of
     the Stock Purchase Contracts and Stock Purchase Units shall be and remain
     effective and Alliant shall have complied with the terms and conditions of
     such order;

          b. Alliant's Board of Directors, or one or more officers duly
     authorized thereby, shall have taken such action to authorize (i) the form
     and substance of the Stock Purchase Contracts and the documents evidencing
     and used in connection with the issuance and sale of the Stock Purchase
     Units and (ii) the issuance and sale of such Stock Purchase Contracts and
     Stock Purchase Units;

          c. Such Stock Purchase Contracts and Stock Purchase Units shall have
     been duly executed and delivered in accordance with their respective terms
     and provisions; and

          d. Such Stock Purchase Contracts and Stock Purchase Units shall have
     been issued and sold for the consideration contemplated by, and otherwise
     in conformity with, the Registration Statement, as supplemented by a
     Prospectus Supplement with respect to such issuance and sale, and the acts,
     proceedings and documents referred to above.




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Alliant Energy Corporation
Alliant Energy Resources, Inc.
April 1, 2003
Page 4

     We are qualified to practice law in the State of Wisconsin and we do not
purport to be experts on the law other than that of the State of Wisconsin and
the federal laws of the United States of America. We express no opinion as to
the laws of any jurisdiction other than the State of Wisconsin and the federal
laws of the United States. To the extent matters covered by our opinion are
governed by the laws of a jurisdiction other than the State of Wisconsin, we
have assumed, without independent investigation, that the applicable laws of
such jurisdiction are identical in all relevant respects to the substantive laws
of the State of Wisconsin.

     We hereby consent to the reference to our firm under the caption "Legal
Matters" in the Prospectus which is filed as part of the Registration Statement,
and to the filing of this opinion as an exhibit to the Registration Statement.
In giving this consent, we do not admit that we are "experts" within the meaning
of Section 11 of the Securities Act or within the category of persons whose
consent is required by Section 7 of the Securities Act.

                                     Very truly yours,

                                     /s/ Foley & Lardner

                                     FOLEY & LARDNER