EXHIBIT 23 ---------- CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM We hereby consent to the incorporation by reference in the Registration Statements on Form S-3 (Nos. 353-112766 and 333-115043) and Form S-8 (Nos. 33-83160 and 33-06565) of Zoltek Companies, Inc. of our report dated December 29, 2004, relating to the consolidated financial statements and financial statement schedule of Zoltek Companies, Inc., which appears in this Form 10-K. /s/PricewaterhouseCoopers LLP - ----------------------------- PricewaterhouseCoopers LLP St. Louis, Missouri December 29, 2004