EXHIBIT 99.1


                      CHIEF EXECUTIVE OFFICER CERTIFICATION
            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, John H. Castle, the Chief Executive Officer
of Southern Michigan Bancorp, Inc. (the "Company") hereby certifies that, to the
best of his knowledge:

         1. The Company's Annual Report on Form 10-K for the year ended December
31, 2002, and to which this Certification is attached as Exhibit 99.1 (the
"Annual Report"), fully complies with the requirements of Section 13(a) or 15(d)
of the Securities Exchange Act of 1934; and

         2. The information contained in the Annual Report fairly presents, in
all material respects, the financial condition and results of operations of the
Company.

Date:  March 26, 2003

                                     /s/ John H. Castle
                                     -------------------------------------------
                                     John H. Castle
                                     Chief Executive Officer


This certification accompanies the Annual Report pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002 and shall not, except to the extent required by the
Sarbanes-Oxley Act of 2002, be deemed filed by the Company for the purposes of
Section 18 of the Securities Exchange Act of 1934, as amended.



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