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                                                                 Exhibit 31.1

                                CERTIFICATION
                                -------------

I, Zsolt Rumy, certify that:

     (1)  I have reviewed this quarterly report on Form 10-Q of Zoltek
          Companies, Inc.;

     (2)  Based on my knowledge, this quarterly report does not contain any
          untrue statement of a material fact or omit to state a material
          fact necessary in order to make the statements made, in light of
          the circumstances under which such statements were made, not
          misleading with respect to the period covered by this quarterly
          report;

     (3)  Based on my knowledge, the financial statements, and other
          financial information included in this quarterly report, fairly
          present in all material respects the financial condition, results
          of operations and cash flows of the registrant as of, and for, the
          periods presented in this quarterly report;

     (4)  The registrant's other certifying officer and I are responsible
          for establishing and maintaining disclosure controls and
          procedures (as defined in Exchange Act Rules 13a-14 and 15d-14)
          for the registrant and have:

          (a)  designed such disclosure controls and procedures, or caused
               such disclosure controls and procedures to be designed under
               our supervision, to ensure that material information relating
               to the registrant, including its consolidated subsidiaries,
               is made known to us by others within those entities,
               particularly during the period for which this quarterly
               report is being prepared;

          (b)  evaluated the effectiveness of the registrant's disclosure
               controls and procedures and presented in this report our
               conclusions about the effectiveness of the disclosure
               controls and procedures, as of the end of the period covered
               by this quarterly report based on such evaluation; and

          (c)  disclosed in this report any change in the registrant's
               internal control over financial reporting that occurred
               during the registrant's most recent fiscal quarter that has
               materially affected, or is reasonably likely to materially
               affect, the registrant's internal control over financial
               reporting; and

     (5)  The registrant's other certifying officer and I have disclosed,
          based on our most recent evaluation of internal control over
          financial reporting, to the registrant's auditors and the audit
          committee of the registrant's board of directors (or persons
          performing the equivalent function):

          (a)  all significant deficiencies and material weaknesses in the
               design or operation of internal controls which are reasonably
               likely to adversely affect the registrant's ability to
               record, process, summarize and report financial information;
               and

          (b)  any fraud, whether or not material, that involves management
               or other employees who have a significant role in the
               registrant's internal controls over financial report.

August 9, 2005                            /s/ ZSOLT RUMY
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                                          Zsolt Rumy
                                          Chief Executive Officer