As filed with the Securities and Exchange Commission on July 26, 2004

Registration No. 333-_____

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

_________________

FORM S-8
REGISTRATION STATEMENT
Under
THE SECURITIES ACT OF 1933

_________________

ALLIANT ENERGY CORPORATION

(Exact name of registrant as specified in its charter)

Wisconsin	39-1380265
(State or other jurisdiction of	(I.R.S. Employer
incorporation or organization)	Identification No.)
4902 North Biltmore Lane
Madison, Wisconsin	53718-2132
(Address of principal executive offices)	(Zip Code)

Alliant Energy Corporation 401(k) Savings Plan

(Full title of the plan)

_________________

F.J. Buri	Copy to:
Corporate Secretary
Alliant Energy Corporation	Benjamin F. Garmer, III
4902 North Biltmore Lane	Jay O. Rothman
Madison, Wisconsin 53718-2132	Foley & Lardner LLP
(608) 458-3311	777 East Wisconsin Avenue
(Name, address and telephone number,	Milwaukee, Wisconsin 53202-5306
including area code, of agent for service)	(414) 271-2400

_________________

CALCULATION OF REGISTRATION FEE


Title of Securities to be Registered	Amount to be Registered	Proposed Maximum Offering Price Per Share	Proposed Maximum Aggregate Offering Price	Amount of Registration Fee
Common Stock,	1,600,000 shares	$26.49 (1)	$42,384,000 (1)	$5,370.06
$.01 par value
Common Share	1,600,000 rights	(2)	(2)	(2)
Purchase Rights

(1)	Estimated pursuant to Rule 457(c) and (h) under the Securities Act of 1933 solely for the purpose of calculating the registration fee based on the average of the high and low prices for Alliant Energy Corporation Common Stock on the New York Stock Exchange Composite Tape on July 23, 2004.

(2)	The value attributable to the Common Share Purchase Rights is reflected in the market price of the Common Stock to which the Rights are attached.

_________________

In addition, pursuant to Rule 416(c) under the Securities Act of 1933, this Registration Statement also covers an indeterminate amount of interests to be offered or sold pursuant to the employee benefit plan described herein.

PART I

INFORMATION REQUIRED IN THE SECTION 10(a) PROSPECTUS

The document or documents containing the information specified in Part I are not required to be filed with the Securities and Exchange Commission (the “Commission”) as part of this Registration Statement on Form S-8.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

Item 3. Incorporation of Documents by Reference .

The following documents filed with the Commission by Alliant Energy Corporation (the “Company”) or the Alliant Energy Corporation 401(k) Savings Plan (the “Plan”) are hereby incorporated herein by reference:

1. The Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2003.

2. The Plan’s Annual Report on Form 11-K for the fiscal year ended December 31, 2003.

3. The Company’s Quarterly Report on Form 10-Q for the quarter ended March 31, 2004.

4. The description of the Company’s Common Stock contained in Item 4 of the Company’s Registration Statement on Form 8-B, dated April 1, 1988, including any amendment or report filed for the purpose of updating such description.

5. The description of the Company’s Common Share Purchase Rights contained in Item 1 of the Company’s Registration Statement on Form 8-A, dated January 20, 1999, including any amendment or report filed for the purpose of updating such description.

All documents subsequently filed by the Company or the Plan pursuant to Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended, after the date of filing of this Registration Statement and prior to such time as the Company files a post-effective amendment to this Registration Statement which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold shall be deemed to be incorporated by reference in this Registration Statement and to be a part hereof from the date of filing of such documents.

Item 4. Description of Securities .

Not applicable.

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Item 5. Interests of Named Experts and Counsel .

None.

Item 6. Indemnification of Directors and Officers .

Pursuant to the Wisconsin Business Corporation Law and the Company’s By-laws, as amended, directors and officers of the Company are entitled to mandatory indemnification from the Company against certain liabilities 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 the defense thereof, unless it is determined that the director or officer breached or failed to perform his or her duties to the Company and such breach or failure constituted: (a) a willful failure to deal fairly with the Company or its shareowners in connection with a matter in which the director or officer had a material conflict of interest; (b) a violation of the criminal law, unless the director or officer had 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. The Wisconsin Business Corporation Law specifically states that it is the policy of Wisconsin to require or permit indemnification in connection with a proceeding involving securities regulation, as described therein, to the extent required or permitted as described above. Additionally, under the Wisconsin Business Corporation Law, directors of the Company are not subject to personal liability to the Company, its shareowners 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 in subparagraphs (a) through (d) outlined above.

The indemnification provided by the Wisconsin Business Corporation Law and the Company’s By-laws is not exclusive of any other rights to which a director or officer may be entitled. The general effect of the foregoing provisions may be to reduce the circumstances which an officer or director may be required to bear the economic burden of the foregoing liabilities and expenses.

The Company maintains a liability insurance policy for its directors and officers as permitted by Wisconsin law which may extend to, among other things, liability arising under the Securities Act of 1933, as amended.

Item 7. Exemption from Registration Claimed .

Not applicable.

Item 8. Exhibits .

The exhibits filed herewith or incorporated herein by reference are set forth in the attached Exhibit Index.

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The undersigned Registrant hereby undertakes that it has submitted or will submit the Plan, and any amendment thereto, to the Internal Revenue Service (“IRS”) in a timely manner and has made or will make all changes required by the IRS in order to continue the qualification of the Plan under Section 401 of the Internal Revenue Code of 1986, as amended.

Item 9. 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;

(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 information required to be included in a post-effective amendment by those paragraphs is contained in periodic reports filed with or furnished to the Commission 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 herein, 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) The undersigned Registrant 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 this Registration Statement shall be deemed to be a new registration statement relating to the securities offered herein, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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(c) Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the Registrant pursuant to the foregoing provisions, or otherwise, the Registrant has been advised that in the opinion of the Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the Registrant of expenses incurred or paid by a director, officer or controlling person of the 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, the Registrant 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.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Madison, State of Wisconsin, on this 26th day of July, 2004.

	ALLIANT ENERGY CORPORATION
	By: /s/ Erroll B. Davis, Jr.
	Erroll B. Davis, Jr.
	Chairman and Chief Executive Officer

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

Signature	Title	Date
/s/ Erroll B. Davis, Jr	Chairman and Chief Executive Officer	July 26, 2004
Erroll B. Davis, Jr	and Director (Principal Executive
	Officer)
/s/ Eliot G. Protsch	Senior Executive Vice President and	July 26, 2004
Eliot G. Protsch	Chief Financial Officer (Principal
	Financial Officer)
/s/ John E. Kratchmer	Vice President-Controller and Chief	July 26, 2004
John E. Kratchmer	Accounting Officer (Principal
	Accounting Officer)
*	Director	July 26, 2004
Michael L. Bennett
*	Director	July 26, 2004
Jack B. Evans
*	Director	July 26, 2004
Katharine C. Lyall
*	Director	July 26, 2004
Singleton B. McAllister

S-1

Signature	Title	Date

*	Director	July 26, 2004
Ann K. Newhall
*	Director	July 26, 2004
David A. Perdue
*	Director	July 26, 2004
Judith D. Pyle
*	Director	July 26, 2004
Robert W. Schlutz
*	Director	July 26, 2004
Anthony R. Weiler

*By:	/s/ Erroll B. Davis, Jr. Erroll B. Davis, Jr. Attorney-in-Fact

S-2

Pursuant to the requirements of the Securities Act of 1933, the Alliant Energy Corporation Employee Total Compensation Committee, which administers the Plan, has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Madison and State of Wisconsin, on this 26th day of July, 2004.

	ALLIANT ENERGY CORPORATION
	401(k) SAVING PLAN
	/s/ Jonathan Day
	Jonathan Day
	/s/ John E. Kratchmer
	John E. Kratchmer
	/s/ Eric D. Mott
	Eric D. Mott
	/s/ Joel Schmidt
	Joel Schmidt
	/s/ Joan Thompson
	Joan Thompson
	The foregoing persons are all of the members of the Alliant Energy
	Corporation Employee Total Compensation Committee which is the current
	administrator of the Alliant Energy Corporation 401(k) Savings Plan.

S-3

EXHIBIT INDEX

Exhibit
Number

Exhibit Description

(4.1)

Restated Articles of Incorporation of Alliant Energy Corporation, as amended.

(4.2)

Alliant Energy Corporation 401(k) Savings Plan, as amended (incorporated by reference to Exhibit 4.2 to the Company's Registration Statement on Form S-8, dated May 15, 2002 (File No. 333-88306)).

(4.3)

Rights Agreement, dated as of January 20, 1999, between Alliant Energy Corporation and Wells Fargo Bank Minnesota, N.A., successor (incorporated by reference to Exhibit 4.1 to the Company's Registration Statement on Form 8-A, dated January 20, 1999 (File No. 1-9894)).

(5)	Opinion of Foley & Lardner LLP.

(23.1)

Consent of Deloitte & Touche LLP.

(23.2)

Consent of Foley & Lardner LLP (contained in Exhibit (5)).

(24)	Powers of Attorney.

E-1

RESTATED
ARTICLES OF INCORPORATION
OF
ALLIANT ENERGY CORPORATION

Pursuant to Section 180.1007 of the Wisconsin Business Corporation Law, these Restated Articles of Incorporation shall supersede and take the place of the corporation’s heretofore existing Restated Articles of Incorporation and all prior amendments thereto.

ARTICLE I

The name of the corporation is Alliant Energy Corporation.

ARTICLE II

The period of existence of the corporation shall be perpetual.

ARTICLE III

The corporation is organized for the purpose of engaging in any lawful activities within the purposes for which corporations may be organized under Chapter 180 of the Wisconsin Statutes, as amended from time to time.

ARTICLE IV

The corporation shall have authority to issue two hundred forty million (240,000,000) shares of common stock, $.01 par value.

ARTICLE V

No holder of any capital stock of the corporation shall have any preemptive right to purchase, acquire to subscribe to any capital stock or other securities issued or sold by the Corporation, including any such capital stock or securities now or hereafter authorized.

ARTICLE VI

The address of the registered office of the corporation is 4902 North Biltmore Lane, P. O. Box 77007, Madison, Wisconsin 53707-1007, and the name of the registered agent of the corporation at such address is F. J. Buri.

ARTICLE VII

The corporation reserves the right to increase or decrease its authorized capital stock or any class or series thereof, or to reclassify the same.

ARTICLE VIII

The number of directors constituting the Board of Directors shall be as fixed from time to time by the Bylaws of the Corporation, but shall not be less than seven (7). Each director shall be a stockholder of the Corporation. The directors of the Corporation shall be divided into three classes as nearly equal in number as possible, to serve for staggered three-year terms or until their respective successors are duly elected and qualified. The initial directors of the Corporation shall be those persons who, at the time of the effectiveness of the merger of the Corporation’s subsidiary, WPL Acquisitions, Inc., into the Corporation’s subsidiary, Wisconsin Power and Light Company, are serving as directors of Wisconsin Power and Light Company, each to hold office for the term for which such person was elected a director of Wisconsin Power and Light Company. Beginning with the Corporation’s annual meeting of stockholders in 1988, the successors of the class of directors whose terms shall then expire shall be elected to hold office for a term expiring a the third annual meeting of stockholders after their election or until their respective successors are duly elected and qualified. If, at any annual meeting of stockholders, directors of more than one class are to be elected, each class of directors to be elected at such meeting shall be nominated and voted for in a separate election. Any vacancy occurring in the Board of Directors, including a vacancy created by an increase in the number of directors, shall be filled until the next succeeding annual meeting of stockholders by the majority vote of the directors then in office, even if less than a quorum.

* * *

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		FOLEY & LARDNER LLP ATTORNEYS AT LAW
		777 East Wisconsin Avenue, Suite 3800 Milwaukee, Wisconsin 53202-5306 414.271.2400 TEL 414.297.4900 FAX www.foley.com
	July 26, 2004
		CLIENT/MATTER NUMBER 031613-0153

Alliant Energy Corporation
4902 North Biltmore Lane
Madison, Wisconsin 53718-2132

Ladies and Gentlemen:

We have acted as counsel for Alliant Energy Corporation, a Wisconsin corporation (the “Company”), in conjunction with the preparation of a Registration Statement on Form S-8 (the “Registration Statement”) to be filed by the Company with the Securities and Exchange Commission under the Securities Act of 1933, as amended (the “Securities Act”), relating to 1,600,000 shares of the Company’s Common Stock, $.01 par value (the “Common Stock”), the related Common Share Purchase Rights (the “Rights”), and interests in the Alliant Energy Corporation 401(k) Savings Plan, as amended to date (the “Plan”), which may be issued or acquired pursuant to the Plan. The terms of the Rights are as set forth in that certain Rights Agreement, dated as of January 20, 1999, by and between the Company and Wells Fargo Bank Minnesota, N.A. (the “Rights Agreement”).

As such counsel, we have examined: (i) the Plan; (ii) the Registration Statement; (iii) the Rights Agreement; (iv) the Company’s Restated Articles of Incorporation and By-Laws, as amended to date; (v) resolutions of the Company’s Board of Directors relating to the Plan and the issuance of securities thereunder; and (vi) such other corporate proceedings, documents and records as we have deemed necessary to enable us to render this opinion.

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

1. The Company is a corporation validly existing under the laws of the State of Wisconsin.

2. It is presently contemplated that the shares of Common Stock to be acquired by the Plan will either be purchased in the open market or purchased directly from the Company. To the extent that the shares of Common Stock to be acquired by the Plan shall constitute shares newly issued by and purchased from the Company, such shares of Common Stock, when issued by the Company pursuant to the terms and conditions of the Plan, and as contemplated by the Registration Statement, will be validly issued, fully paid and nonassessable and no personal liability will attach to the ownership thereof, except with respect to wage claims of, or other debts owing to, employees of the Company 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.

3. The Rights, when issued pursuant to the terms of the Rights Agreement, will be validly issued.


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

Alliant Energy Corporation
July 26, 2004
Page 2

We consent to the use of this opinion as an exhibit to the Registration Statement. In giving our 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 LLP

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in this Registration Statement of Alliant Energy Corporation on Form S-8 of (1) our report dated March 3, 2004 (which report expresses an unqualified opinion and includes an explanatory paragraph relating to the adoption of Statement of Financial Accounting Standards No. 143, “Accounting for Asset Retirement Obligations”) appearing in the Annual Report on Form 10-K of Alliant Energy Corporation for the year ended December 31, 2003, and (2) our report dated June 14, 2004 appearing in the Annual Report on Form 11-K of Alliant Energy Corporation 401(k) Savings Plan for the year ended December 31, 2003.

/s/ Deloitte & Touche LLP

Milwaukee, Wisconsin
July 26, 2004

POWER OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, That I

Michael L. Bennett

hereby constitute and appoint Erroll B. Davis, Jr., William D. Harvey, Eliot G. Protsch and F. J. Buri, and each of them individually, my true and lawful attorney-in-fact and agent, with full power of substitution and resubstitution, for me and in my name, place and stead, in any and all capacities, to sign my name as a director of Alliant Energy Corporation to the Registration Statement on Form S-8 and any amendments (including post-effective amendments) or supplements thereto, relating to the securities to be offered and sold pursuant to the Alliant Energy Corporation 401(k) Savings Plan, as amended, and to file the same, with all exhibits thereto, and other documents in connection therewith, with the Securities and Exchange Commission in connection with the registration of the above-referenced Securities under the Securities Act of 1933, as amended.