Exhibit 32.1

                          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 Zoltek Companies, Inc. (the
"Company") on Form 10-Q for the period ending March 31, 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:  May 10, 2006                           By:     /s/ ZSOLT RUMY
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                                                        Zsolt Rumy
                                                 Chief Executive Officer