Exhibit 99(c) Certification by the Chief Executive Officer and Chief Financial Officer Pursuant to 18 U.S.C. Section 1350, as Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 Pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, each of the undersigned officers of Associated Banc-Corp, a Wisconsin corporation (the "Company"), does hereby certify that: 1. The accompanying Quarterly Report of the Company on Form 10-Q for the period ended June 30, 2003 (the "Report"), fully complies with the requirements of Section 13(a) of the Securities Exchange Act of 1934; and 2. Information contained in the Report fairly presents, in all material respects, the financial condition and results of operations of the Company. /s/ Paul S. Beideman Chief Executive Officer August 13, 2003 /s/ Joseph B. Selner Chief Financial Officer August 13, 2003