UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington D. C. 20549 PUBLIC UTILITY HOLDING COMPANY ACT OF 1935 File No. 70-10052 REPORT PERIOD January 1, 2005 through March 31, 2005. In the Matter of ALLIANT ENERGY CORPORATION, ET AL ALLIANT ENERGY CORPORATION ("AEC") hereby certifies on behalf of itself, Interstate Power and Light Company ("IPL") and Wisconsin River Power Company ("WRP") that during the period from January 1, 2005 through March 31, 2005 (the "Reporting Period"): 1. Maximum amount of short-term debt outstanding and effective cost during reporting period were as follows: Maximum Range of Short-Term Effective Company Debt Cost IPL $ 39,000,000 2.27 -2.92% AEC $ 0 NA WRP $ 0 NA Said transactions have been carried out in accordance with the terms and conditions of, and for the purpose represented in, the Form U-1 Application-Declaration, as amended, of AEC, et al, in File 70-10249, and in accordance with the terms and conditions of the SEC's order dated December 28, 2004, permitting said Application-Declaration to become effective. DATED: May 13, 2005 ALLIANT ENERGY CORPORATION INTERSTATE POWER AND LIGHT COMPANY WISCONSIN RIVER POWER COMPANY BY: ALLIANT ENERGY CORPORATION BY: /s/ Thomas L. Hanson ------------------------------ Thomas L. Hanson Vice President and Treasurer