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, 2005 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 20, 2005                           By:       /s/ ZSOLT RUMY
      ------------                              -------------------------------
                                                         Zsolt Rumy
                                                   Chief Executive Officer