Exhibit 99.1

[Zoltek logo]


FOR IMMEDIATE RELEASE                              NASDAQ NMS SYMBOL: "ZOLT"
- ---------------------                              -------------------------

            ZOLTEK INCREASES CONVERTIBLE DEBT FINANCING PACKAGE
            ---------------------------------------------------

         ST. LOUIS, MISSOURI -- APRIL 28, 2006 -- Zoltek Companies, Inc.
today announced that it has amended the terms of its previously announced
$50 million convertible debt financing package with institutional investors
to provide for an additional $10 million of funding. Zoltek has previously
drawn a total of $30 million under the financing package, and the amendment
provides for Zoltek to issue $30 million of convertible debt and warrants.

         In connection with the amendment, the institutional investors have
agreed to convert the entire $20 million aggregate principal amount of
convertible notes previously issued by Zoltek to the investors in February
2005 into approximately 1,000,000 shares of common stock and to exercise
associated warrants for approximately 1,052,000 shares of common stock. The
conversion of the notes and exercise of the related warrants by the
investors will eliminate future derivative accounting treatment for these
instruments which resulted in Zoltek recording non-cash expense or income
arising from fluctuations in the market price of Zoltek's shares and
corresponding changes in the fair value of the convertible notes and
warrants. Consequently, beginning with the quarter ending June 30, 2006,
Zoltek will no longer report its convertible debt financings on a derivative
accounting basis.

         Under the amendment of the convertible debt financing package, the
terms of the previous financing package have been revised to provide for
additional funding of up to $30 million in two separate closings of $20
million and $10 million, respectively. Zoltek anticipates that the first of
the two fundings will be completed in the next few weeks. The amendment
provides that the additional $30 million of convertible notes, which will be
secured by certain assets of the Company's Hungarian operations, will be
convertible into Zoltek common stock at a conversion price of $25.51 per
share. The convertible notes will mature 42 months from the closing date and
will bear interest at a fixed rate of 7.5% per annum for 18 months, and
thereafter at LIBOR plus 4% per annum. In connection with issuance of the
additional $30 million of convertible notes, Zoltek will issue to the
investors five-year warrants to purchase an aggregate of up to 411,521
shares of common stock at an exercise price of $28.06 per share, and up to
111,113 shares of common stock at an exercise price of $.01 per share. The
other terms of the remaining convertible notes and warrants to be issued are
essentially the same as those of the convertible notes and warrants
previously issued under the convertible financing package.

                      FOR FURTHER INFORMATION CONTACT:
                    ZSOLT RUMY, CEO OR KEVIN SCHOTT, CFO
                             3101 MCKELVEY ROAD
                             ST. LOUIS, MO 63044
                               (314) 291-5110

This press release contains forward-looking statements, which are based upon
the current expectations of the Company. Because these forward-looking
statements are inherently subject to risks and uncertainties, there are a
number of factors that could cause the Company's plans, actions and actual
results to differ materially. Among these factors are the Company's ability
to: re-activate its formerly idle manufacturing facilities on a timely and
cost-effective basis, to meet current order levels for carbon fibers;
successfully add new capacity for the production of carbon fiber and
precursor raw material; execute plans to exit its specialty products
business and reduce costs; achieve profitable operations; raise new capital
and increase its borrowing at acceptable costs; manage changes in customers'
forecasted requirements for the Company's products; continue investing in
application and market development; manufacture low-cost carbon fibers and
profitably market them; and penetrate existing, identified and emerging
markets. The timing and occurrence (or non-occurrence) of transactions and
events that determine the future effect of these factors on the Company, as
well as other factors, may be beyond the control of the Company. The Company
undertakes no obligation to update any forward-looking statement to reflect
events or circumstances after the date of this press release.