Exhibit 32.1
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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, 2006 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:  December 27, 2006                     By: /s/ Zsolt Rumy
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                                                     Zsolt Rumy
                                                     Chief Executive Officer