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                                                                 Exhibit 31.1

                                CERTIFICATION
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I, Zsolt Rumy, certify that:

    (1) I have reviewed this quarterly report on Form 10-Q/A 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 reporting.

December 16, 2005                              /s/ ZSOLT RUMY
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                                               Zsolt Rumy
                                               Chief Executive Officer