Ownership Submission
FORM 4
Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
PROTSCH ELIOT G
  2. Issuer Name and Ticker or Trading Symbol
ALLIANT ENERGY CORP [LNT]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
_____ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
SENIOR EXEC VP & CFO
(Last)
(First)
(Middle)
PO BOX 2568
3. Date of Earliest Transaction (Month/Day/Year)
02/15/2007
(Street)

MADISON, WI 53701
4. If Amendment, Date Original Filed(Month/Day/Year)
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code
(Instr. 8)
4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5)
5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4)
6. Ownership Form: Direct (D) or Indirect (I)
(Instr. 4)
7. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V Amount (A) or (D) Price
COMMON 02/15/2007   M   11,798 A $ 31.54 11,798 D  
COMMON 02/15/2007   S   11,798 D $ 42.3633 0 D  
COMMON 02/15/2007   M   16,642 A $ 27.79 16,642 D  
COMMON 02/15/2007   S   16,642 D $ 42.3633 0 D  
COMMON 02/15/2007   M   11,099 A $ 24.9 11,099 D  
COMMON 02/15/2007   S   11,099 D $ 42.3633 0 D  
COMMON 02/15/2007   M   7,071 A $ 29.875 7,071 D  
COMMON 02/15/2007   S   7,071 D $ 42.3633 0 D  
COMMON DRIP               7,098.7512 D  
401(k)               18,435.4875 D  
COMMON (RESTRICTED)               34,004.0915 D  

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction Code
(Instr. 8)
5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4, and 5)
6. Date Exercisable and Expiration Date
(Month/Day/Year)
7. Title and Amount of Underlying Securities
(Instr. 3 and 4)
8. Price of Derivative Security
(Instr. 5)
9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 4)
10. Ownership Form of Derivative Security: Direct (D) or Indirect (I)
(Instr. 4)
11. Nature of Indirect Beneficial Ownership
(Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
EMP. STOCK OPTION (Right to Buy) $ 24.9 02/15/2007   M     11,099 01/02/2005 01/02/2014 COMMON 11,099 $ 0 10,000 D  
EMP. STOCK OPTION (Right to Buy) $ 27.79 02/15/2007   M     16,642 05/16/2005 05/16/2012 COMMON 16,642 $ 0 10,000 D  
EMP. STOCK OPTION (Right to Buy) $ 29.875 02/15/2007   M     7,071 06/01/2002 06/01/2009 COMMON 7,071 $ 0 0 D  
EMP. STOCK OPTION (Right to Buy) $ 31.54 02/15/2007   M     11,798 01/02/2003 01/02/2011 COMMON 11,798 $ 0 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
PROTSCH ELIOT G
PO BOX 2568
MADISON, WI 53701
      SENIOR EXEC VP & CFO  

Signatures

 F. J. Buri as POA for   02/16/2007
**Signature of Reporting Person Date

Explanation of Responses:

* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.

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