EXHIBIT 99.1
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                            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 Annual Report of Zoltek Companies, Inc. (the "Company")
on Form 10-K for the period ending September 30, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I, Zsolt
Rumy, Chief Executive Officer 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, to the best of my knowledge and belief, 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.


Date: February 18, 2003                      By: /s/ Zsolt Rumy
                                                 ----------------------------
                                                          Zsolt Rumy
                                                   Chief Executive Officer