# Exhibit 31.1

Certification of the
Chairman and Chief Executive Officer  of Alliant Energy Corporation

I, Erroll B. Davis, Jr., certify
that:

|1. |  | I
have reviewed this annual report on Form 10-K of Alliant Energy Corporation;
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|2. |  | Based
on my knowledge, this report does not contain any untrue statement of a material fact or
omit to state a material fact      necessary to make the statements made, in light of the
circumstances under which such statements were made, not misleading with      respect to
the period covered by this report;
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|3. |  | Based
on my knowledge, the financial statements, and other financial information included in
this report, fairly present in      all material respects the financial condition,
results of operations and cash flows of the registrant as of, and for, the periods
     presented in this report;
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|4. |  | The
registrant's other certifying officer(s) and I are responsible for establishing and
maintaining disclosure controls and      procedures (as defined in Exchange Act Rules
13a-15(e) and 15d-15(e)) for the registrant and have:
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| | a) |  | Designed
such disclosure controls and procedures, or caused such disclosure controls and
procedures to be designed under our          supervision, to ensure that material
information relating to the registrant, including its consolidated subsidiaries, is
         made known to us by others within those entities, particularly during the period
in which this report is being prepared;
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| | b) |  | Evaluated
the effectiveness of the registrant's disclosure controls and procedures and presented in
this report our          conclusions about the effectiveness of the disclosure controls
and procedures, as of the end of the period covered by this          report based on such
evaluation; and
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| | c) |  | Disclosed
in this report any change in the registrant's internal control over financial reporting
that occurred during the          registrant's most recent fiscal quarter (the
registrant's fourth fiscal quarter in the case of an annual report) that has
         materially affected, or is reasonably likely to materially affect, the
registrant's internal control over financial          reporting; and
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|5. |  | The
registrant's other certifying officer(s) and I have disclosed, based on our most recent
evaluation of internal control      over financial reporting, to the registrant's
auditors and the audit committee of the registrant's board of directors (or persons
     performing the equivalent functions):
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| | a) |  | All
significant deficiencies and material weaknesses in the design or operation of internal
control over financial reporting          which are reasonably likely to adversely affect
the registrant's ability to record, process, summarize and report financial
         information; and
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| | b) |  | Any
fraud, whether or not material, that involves management or other employees who have a
significant role in the          registrant's internal control over financial reporting.
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Date: March 11,
2004

| | /s/ Erroll B. Davis, Jr.
| | ------------------------
| | Erroll B. Davis, Jr.    
| | Chairman and            
| | Chief Executive Officer