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 Quarterly Report on Form 10-Q for the period ended
          September 30, 2002, and to which this Certification is attached as
          Exhibit 99.1 (the "Periodic 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 Periodic Report fairly presents, in
          all material respects, the financial condition and results of
          operations of the Company.


Date:  November 13, 2002
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                                      /s/ John H. Castle
                                      ----------------------------------------
                                      John H. Castle, Chief Executive Officer


This certification accompanies the Periodic 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.