EXHIBIT 99(a)



                         CORE MOLDING TECHNOLOGIES, INC.

                            CERTIFICATION PURSUANT TO
                             18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002


         In connection with the Quarterly Report of Core Molding Technologies,
Inc. (the "Company") on Form 10-Q for the period ending March 31, 2003 as filed
with the Securities and Exchange Commission on the date hereof (the "Report"),
I, James L. Simonton, President, Chief Executive Officer and Director of the
Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to
Section 906 of the Sarbanes-Oxley Act of 2002 that:

         (1)      The 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 Report fairly presents, in
                  all material respects, the financial condition and results of
                  operations of the Company.


                           /s/ James L. Simonton
                               -----------------------------------------------
                               James L. Simonton
                               President, Chief Executive Officer and Director
                               May 14, 2003


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