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/A for the period ending December 31, 2004 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 16, 2005                    By:     /s/ ZSOLT RUMY
      -----------------                       ---------------------------
                                                      Zsolt Rumy
                                                Chief Executive Officer