Document:

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                                                               Exhibit 10.13

                               PROMISSORY NOTE
                               ---------------

$6,000,000.00                                               JANUARY 13, 2004

         FOR VALUE RECEIVED, ZOLTEK COMPANIES, INC., a Missouri corporation,
and ZOLTEK PROPERTIES, INC., a Missouri corporation (individually and
collectively, "Maker"), do hereby jointly and severally promise to pay to
the order of BEAL BANK, S.S.B., a savings bank organized under the laws of
the State of Texas ("Payee"), at its office at 6000 Legacy Drive, 4 East,
Plano, Texas 75024, or at such other place as the holder hereof may from
time to time designate in writing, in lawful money of the United States, the
principal sum of SIX MILLION AND NO/100 DOLLARS ($6,000,000.00), or so much
thereof as is advanced on the loan evidenced hereby pursuant to the Loan
Agreement, as hereinafter defined, with interest thereon as provided in this
Note.

         1.       CERTAIN DEFINITIONS. For the purposes hereof, the terms set
                  -------------------
forth below shall have the following meanings:

                  (a)      "Applicable Law" shall mean (i) the laws of the
         United States of America applicable to contracts made or performed
         in the State of Texas, now or at any time hereafter prescribing
         maximum rates of interest or eliminating maximum rates of interest
         on loans and extensions of credit, (ii) the laws of the State of
         Texas, including, without limitation, Chapter 303 of the Texas
         Finance Code, as the same may be amended from time to time
         ("Chapter 303") now or at any time hereafter prescribing or
         eliminating maximum rates of interest on loans and extensions of
         credit, and (iii) any other laws at any time applicable to
         contracts made or performed in the State of Texas which permit a
         higher interest rate ceiling hereunder.

                  (b)      "Alternate Base Rate" shall mean the per annum rate
         equal to the greater of (i) thirteen percent (13%); or (ii) the sum
         of (x) The Wall Street Journal Prime Rate, as hereinafter defined,
         as it fluctuates from time to time, plus (y) nine percent (9%), but
         not in excess of the Highest Lawful Rate; provided, however, until
         Payee has received and approved the Updated Surveys (as defined in
         the Loan Agreement) in accordance with the terms of the Loan
         Agreement and all issues revealed thereby have been resolved to the
         Payee's satisfaction, the rate referenced in clause (i) above will
         be fifteen and one-half percent (15.5%) for the first sixty (60)
         days following the funding of this Note, then sixteen and one-half
         percent (16.5%) for the next sixty (60) days thereafter, then
         seventeen percent (17%) thereafter (until the aforementioned
         Updated Surveys have been delivered and any related issues have
         been resolved to Payee's satisfaction as aforesaid).

                  (c)      "Base Rate" shall mean the per annum rate equal to
         the greater of (i) thirteen percent (13%); or (ii) the sum of (x) the
         One-Year LIBOR Rate, as hereinafter defined, as it fluctuates from
         time to time, plus (y) eleven percent (11%), but not in excess of
         the Highest Lawful Rate provided, however, until Payee has received
         and approved the Updated Surveys (as defined in the Loan Agreement)
         in accordance with the terms of the Loan Agreement and all issues
         revealed thereby have been resolved to the Payee's satisfaction,
         the rate referenced in clause (i) above will be fifteen and
         one-half

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         percent (15.5%) for the first sixty (60) days following the
         funding of this Note, then sixteen and one-half percent (16.5%)
         for the next sixty (60) days thereafter, then seventeen percent
         (17%) thereafter (until the aforementioned Updated Surveys have
         been delivered and any related issues have been resolved to Payee's
         satisfaction as aforesaid).

                  (d)      "Deed of Trust" shall mean (individually and
         collectively) those certain Deeds of Trust, Security Agreement,
         Assignment of Leases and Rents, and Fixture Filing of even date
         herewith, executed by Maker for the benefit of Payee, encumbering
         the Property (hereinafter defined) as security for this Note and
         certain other indebtedness of Maker to Payee.

                  (e)      "Final Maturity Date" shall mean January 13, 2007.

                  (f)      "Highest Lawful Rate" shall mean at the particular
         time in question the maximum rate of interest which, under
         Applicable Law, Payee is then permitted to charge Maker in regard
         to the loan evidenced by this Note. If the maximum rate of interest
         which, under Applicable Law, Payee is permitted to charge Maker in
         regard to the loan evidenced by this Note shall change after the
         date hereof, the Highest Lawful Rate shall be automatically
         increased or decreased, as the case may be, from time to time as of
         the effective date of each change in the Highest Lawful Rate
         without notice to Maker. For purposes of determining the Highest
         Lawful Rate under the Applicable Law of the State of Texas, the
         applicable rate ceiling shall be the weekly ceiling described in
         and computed in accordance with the provisions of Chapter 303;
         provided, however, that in determining the Highest Lawful Rate, all
         fees and other charges contracted for, charged or received by Payee
         in connection with the loan evidenced by this Note which are either
         deemed interest under Applicable Law or required under Applicable
         Law to be deducted from the principal balance hereof to determine
         the rate of interest charged on this Note shall be taken into
         account. To the extent permitted by Applicable Law, Payee may from
         time to time substitute for the "weekly ceiling" referred to above
         any ceiling under Chapter 303 or any other statute and revise the
         rate, index, formula or provision of law used to compute the rate
         hereunder as provided therein.

                  (g)      "Loan Agreement" shall mean that certain letter loan
         agreement of even date herewith, by and between Maker and Payee
         relating to advances of proceeds of the loan evidenced by this
         Note.

                  (h)      "One-Year LIBOR Rate" shall mean the simple average
         of the rates appearing on the display referred to as the "LIBOR Page"
         on Reuters Monitor Money Rates Service (or on any successor or
         substitute page of such Service, or any successor to or substitute
         for such Service, providing rate quotations comparable to those
         currently provided on such page of such Service, as determined by
         Payee from time to time for purposes of providing quotations of
         interest rates applicable to dollar deposits in the London
         interbank market), on the day which is two (2) business days prior
         to the first day of the applicable Interest Period, as hereinafter
         defined, at the rate for dollar deposits with a maturity comparable
         to such Interest Period. In the event that such rate is not
         available at such time for any reason, then the One-Year LIBOR Rate
         for such Interest Period shall be the average rate (rounded
         upwards, if necessary to the next 1/16 of 1%) at which

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         dollars deposits of $5,000,000.00 and for a maturity comparable to
         such Interest Period are offered by leading banks in immediately
         available funds in the London interbank eurocurrency market on the
         day which is two Business Days prior to the first day of the
         applicable Interest Period (the "Alternate One-Year LIBOR Rate").
         The term "Interest Period" shall mean each 365 day period during
         the term of the Loan. In the event of a change in the interest rate
         applicable to the Loan caused by a change in the One-Year LIBOR
         Rate, the interest rate applicable to the Loan shall be adjusted
         effective at the opening of business on the first day of the
         Interest Period in question.

                  (i)      "Property" shall mean the real and personal property
         located in St. Louis and St. Charles Counties, Missouri and Taylor
         County, Texas, which is more particularly described in the Deed of
         Trust.

                  (j)      "Wall Street Journal Prime Rate" shall mean the
         highest prime rate of interest for commercial borrowings published
         from time to time by The Wall Street Journal, provided that if at
         any time The Wall Street Journal ceases to be published or ceases
         to publish such prime rate, Payee shall select a nationally
         recognized substitute publication comparable to The Wall Street
         Journal for use in determining such prime rate, and Payee shall
         provide written notice to Maker of any such substitution.

         2.       CALCULATION AND PAYMENT OF PRINCIPAL AND INTEREST.
                  -------------------------------------------------

                  (a)      Subject to the provisions of Section 7 hereof,
         interest on the unpaid principal balance hereof from time to time
         outstanding shall be computed at a per annum rate equal to the
         lesser of (i) the Base Rate in effect from time to time and (ii)
         the Highest Lawful Rate. If at any time adequate and reasonable
         means do not exist for ascertaining the One-Year LIBOR Rate or the
         Alternate One-Year LIBOR Rate, or if any legal requirement prevents
         the use of the One-Year LIBOR Rate and the Alternate One-Year LIBOR
         Rate, then Payee shall calculate the interest due hereunder
         utilizing the Alternate Base Rate.

                  (b)      Accrued and unpaid interest, computed as set forth in
         clause (a) above or Section 7 below, whichever is applicable, shall
         be due and payable monthly commencing February 1, 2004 and on the
         first (1st) day of each month thereafter throughout the term of
         this Note.

                  (c)      The unpaid principal balance of and all remaining
         accrued and unpaid interest upon this Note, including interest
         computed at the Base Rate (or Alternate Base Rate, if applicable)
         or the Default Rate (as hereinafter defined), whichever is
         applicable, are due and payable on the maturity date hereof,
         whether such maturity date is the Final Maturity Date or any
         accelerated maturity date.

                  (d)      Interest on this Note shall be computed on the basis
         of three hundred sixty five (365) day or three hundred sixty six
         (366) day years, as the case may be.

                  (e)      If the date for any payment or prepayment hereunder
         falls on a day which is a Saturday, Sunday or legal holiday in the
         State of Texas, then for all purposes of this

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         Note, the same shall be deemed to have fallen on the next following
         business day, and such extension of time shall in such case be
         included in the calculation of interest.

                  (f)      All payments on this Note pursuant to this Section 2
         shall be applied first to the payment of any Late Charge (as
         hereinafter defined) due hereunder, then to the payment of any
         costs or expenses of Payee which are to be reimbursed by Maker as
         provided in the Loan Documents (as such term is defined in the Deed
         of Trust), then to the payment of accrued but unpaid interest
         hereon and then to the payment of the principal balance hereof;
         provided, however, if an Event of Default exists, all payments
         received by Payee in regard to the loan evidenced hereby shall be
         applied as Payee may direct.

         3.       PREPAYMENT. The principal balance of this Note may be prepaid
                  ----------
in whole but not in part (except as provided by the terms of the Loan
Agreement), provided Maker provides to Payee at least ten (10) days'
irrevocable written notice of prepayment and pays to Payee at the time of
the prepayment a prepayment premium in accordance with the following
schedule (but in no event will the prepayment premium be in excess of the
maximum amount allowed by law in regard to this Note):

                                              PREPAYMENT PREMIUM (BASED
                 MONTH OF PREPAYMENT       ON AMOUNT OF PRINCIPAL PREPAID)
                 -------------------       -------------------------------
                         1-12                            10%
                        13-24                             5%
                        25-36                             3%

MAKER HEREBY EXPRESSLY WAIVES ANY RIGHT IT MAY HAVE UNDER TEXAS LAW TO
PREPAY THIS NOTE, IN WHOLE OR IN PART, UPON THE ACCELERATION OF THE MATURITY
DATE OF THIS NOTE OR OTHERWISE, WITHOUT A PREPAYMENT CHARGE, AND AGREES
THAT, EXCEPT AS OTHERWISE PROVIDED IN THIS SECTION 3, IF, FOR ANY REASON, A
PREPAYMENT OF ANY OR ALL OF THIS NOTE IS MADE, WHETHER VOLUNTARILY OR UPON
OR FOLLOWING ANY ACCELERATION OF THE MATURITY DATE OF THIS NOTE BY PAYEE ON
ACCOUNT OF THE OCCURRENCE OF ANY EVENT OF DEFAULT ARISING FOR ANY REASON,
INCLUDING, WITHOUT LIMITATION, ON ACCOUNT OF ANY PROHIBITED OR RESTRICTED
TRANSFER OR DISPOSITION OF THE PROPERTY (EXCEPT FOR (I) INSURANCE PROCEEDS
NOT APPLIED TO RESTORATION OF THE PROPERTY IN ACCORDANCE WITH THE TERMS OF
THE DEED OF TRUST AND (II) CONDEMNATION PROCEEDS), THEN MAKER SHALL BE
OBLIGATED TO PAY, CONCURRENTLY THEREWITH, AS A PREPAYMENT FEE, THE
APPLICABLE SUMS SPECIFIED ABOVE. MAKER HEREBY DECLARES THAT THE PAYEE'S
AGREEMENT TO MAKE THE LOAN AT THE INTEREST RATE AND FOR THE TERM SET FORTH
IN THIS NOTE CONSTITUTES ADEQUATE CONSIDERATION, GIVEN INDIVIDUAL WEIGHT BY
MAKER, FOR THIS WAIVER AND AGREEMENT.

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         4.       WAIVER. Except to the extent otherwise expressly set forth
                  ------
below, Maker and all sureties, endorsers, accommodation parties, guarantors
and other parties now or hereafter liable for the payment of this Note, in
whole or in part, hereby severally (i) waive demand, notice of demand,
presentment for payment, notice of nonpayment, notice of default, protest,
notice of protest, notice of intent to accelerate, notice of acceleration,
notice of dishonor and all other notices, and further waive diligence in
collecting this Note, in taking action to collect this Note, in bringing
suit to collect this Note, or in enforcing this Note or any of the security
for this Note; (ii) agree to any substitution, subordination, exchange or
release of any security for this Note or the release of any party primarily
or secondarily liable for the payment of this Note; (iii) agree that Payee
shall not be required to first institute suit or exhaust its remedies hereon
against Maker or others liable or to become liable for the payment of this
Note or to enforce its rights against any security for the payment of this
Note; and (iv) consent to any extension of time for the payment of this
Note, or any installment hereof, made by agreement by Payee with any person
now or hereafter liable for the payment of this Note, even if Maker is not a
party to such agreement.

         5.       EVENTS OF DEFAULT.
                  -----------------

                  (a)      Upon the happening of any of the following events
         (each an "Event of Default"), Payee may, at its option, declare
         immediately due and payable the entire outstanding principal
         balance of this Note together with all interest accrued and owing
         hereon, plus any other sums payable at the time of such declaration
         pursuant to this Note, and every instrument securing this Note,
         including, without limitation, the Deed of Trust. Events of Default
         include the following:

                           (i)      If (a) Maker shall fail to pay any
                  installment of principal and/or interest under this Note
                  as and when same becomes due and payable in accordance
                  with the terms hereof or any other obligation of Maker to
                  Payee involving the payment of money, or (b) Maker shall
                  default in any other obligation under this Note or the
                  Deed of Trust and/or any other Loan Document which can be
                  cured by the payment of money, and such failure or default
                  described in (a) or (b) above is not cured within five (5)
                  days following the date written notice of such failure is
                  given by or on behalf of Payee to Maker; provided,
                  however, (x) Payee will not be obligated to give such
                  written notice more than twice during any twelve (12)
                  month period, and following the second such notice during
                  a twelve (12) month period, any subsequent default or
                  failure during the then current twelve (12) month period
                  shall constitute an Event of Default without any notice
                  given by or on behalf of Payee and (y) Payee has no
                  obligation to provide any such notice or opportunity to
                  cure to Maker in regard to the payment of this Note on the
                  maturity date hereof, whether such maturity date is the
                  Final Maturity Date or any accelerated maturity date
                  established pursuant to the terms hereof; or

                           (ii)     The occurrence of any Event of Default, as
                  defined in the Deed of Trust, or the occurrence of a
                  default under any other document or instrument evidencing,
                  securing or pertaining to the indebtedness evidenced
                  hereby, which

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                  remains uncured for a period of fifteen (15) days following
                  the date written notice thereof is provided to Borrower.

                  (b)      The failure to exercise the foregoing option upon
         the happening of one or more Events of Default shall not constitute
         a waiver of the right to exercise the same or any other option at
         any subsequent time, and no such failure shall nullify any prior
         exercise of any such option without the express written consent
         of Payee.

         6.       COLLATERAL. This Note is secured by, among other things,
                  ----------
the Deed of Trust, which contains provisions for the acceleration of the
maturity hereof upon the happening of certain events.

         7.       DEFAULT INTEREST; LATE CHARGE. If any installment of principal
                  -----------------------------
and/or interest is not paid on or before the due date thereof or if the
entire unpaid principal balance hereof and accrued but unpaid interest
hereon are not paid on or before the earlier to occur of the Final Maturity
Date or any accelerated maturity date as permitted hereby, all unpaid
amounts of this Note, including principal and interest, shall thereafter
bear interest at a rate of interest (the "Default Rate") equal to the lesser
of (a) the Highest Lawful Rate and (b) seventeen and one-half percent
(17.5%); provided, however, that the obligation to pay such interest is
subject to the limitation contained in the following paragraph. Without
limitation of the rights of Payee if a payment is not paid on the due date
thereof and without limitation of the obligation of Maker to pay such
payments on the due dates thereof, at the option of Payee, Maker will pay a
late charge (the "Late Charge") as required by Payee, not exceeding five
percent (5%) of any installment of principal and/or interest that is not
paid on or before the 5th day of the month in which it is due to cover the
extra expenses involved in handling delinquent payments, subject to the
limitation contained in the following paragraph.

         8.       COMPLIANCE WITH LAW. All agreements between Maker and Payee,
                  -------------------
whether now existing or hereafter arising and whether written or oral, are
hereby limited so that in no contingency, whether by reason of demand or
acceleration of the Final Maturity Date or otherwise, shall the interest
contracted for, charged, received, paid or agreed to be paid to Payee in
regard to the loan evidenced by this Note exceed the maximum amount
permissible under Applicable Law. If, from any circumstance whatsoever,
interest would otherwise be payable to Payee in excess of the maximum amount
permissible under Applicable Law, the interest payable to Payee shall be
reduced to the maximum amount permissible under Applicable Law; and if from
any circumstance Payee shall ever receive anything of value deemed interest
by Applicable Law in excess of the maximum amount permissible under
Applicable Law, an amount equal to the excessive interest shall be applied
to the reduction of the principal hereof and not to the payment of interest,
or if such excessive amount of interest exceeds the unpaid balance of
principal hereof, such excess shall be refunded to Maker. All interest paid
or agreed to be paid to Payee shall, to the extent permitted by Applicable
Law, be amortized, prorated, allocated, and spread throughout the full
period (including any renewal or extension) until payment in full of the
principal so that the interest hereon for such full period shall not exceed
the maximum amount permissible under Applicable Law. Payee expressly
disavows any intent to contract for, charge or receive interest in an amount
which exceeds the maximum amount permissible under Applicable Law. This
paragraph shall control all agreements between Maker and Payee.

                                     6

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         9.       ATTORNEYS' FEES AND COSTS. If an Event of Default shall
                  -------------------------
occur, and in the event that thereafter this Note is placed in the hands of
an attorney for collection, or in the event this Note is collected in whole
or in part through legal proceedings of any nature, then and in any such
case Maker promises to pay on demand by Payee, and, to the extent unpaid
upon such demand, there shall be added to the unpaid principal balance
hereof, all reasonable costs of collection, including, but not limited to,
reasonable attorneys' fees incurred by the holder hereof, on account of such
collection, whether or not suit is filed.

         10.      CUMULATIVE RIGHTS. No delay on the part of the holder of
                  -----------------
this Note in the exercise of any power or right under this Note or under any
other instrument executed pursuant hereto shall operate as a waiver thereof,
nor shall a single or partial exercise of any power or right preclude other
or further exercise thereof or the exercise of any other power or right.
Enforcement by the holder of this Note of any security for the payment
hereof shall not constitute any election by it of remedies so as to preclude
the exercise of any other remedy available to it.

         11.      HEADINGS. The paragraph headings used in this Note are for
                  --------
convenience of reference only, and shall not affect the meaning or
interpretation of this Note.

         12.      NOTICES AND DEMANDS. Any notice or demand to be given
                  -------------------
or to be served upon Maker in connection with this Note must be in writing
and shall be given as provided in the Loan Agreement, addressed to Maker as
follows:

                           3101 McKelvey Road
                           Bridgeton, Missouri 63044

or at such other street address within the continental United States as
Maker may designate from time to time by written notice given to and
received by the holder hereof.

         13.      GOVERNING LAW. THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED
                  -------------
IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS AND THE LAWS OF THE UNITED
STATES APPLICABLE TO TRANSACTIONS IN THE STATE OF TEXAS.

         14.      SUCCESSORS AND ASSIGNS. The term "Payee" shall include all
                  ----------------------
of Payee's successors and assigns to whom the benefits of this Note shall
inure.

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                                   MAKER:
                                   -----

                                   ZOLTEK COMPANIES, INC.,
                                   a Missouri corporation

                                   By: /s/ Zsolt Rumy
                                       -------------------------------------
                                   Name: Zsolt Rumy
                                         -----------------------------------
                                   Title: President
                                          ----------------------------------

                                   ZOLTEK PROPERTIES, INC.,
                                   a Missouri corporation

                                   By: /s/ Zsolt Rumy
                                       -------------------------------------
                                   Name: Zsolt Rumy
                                         -----------------------------------
                                   Title: President
                                          ----------------------------------

                                     8<PAGE>

                                                               Exhibit 10.14

                    SECOND AMENDMENT TO CREDIT AGREEMENT
                    ------------------------------------

         This Second Amendment to Credit Agreement (this "Amendment") is
made and entered into as of the 13th day of January, 2004, by and among
ZOLTEK COMPANIES, INC., a Missouri corporation having its chief executive
office and principal place of business located at 3101 McKelvey Road, St.
Louis, Missouri 63044 ("Parent"), ZOLTEK CORPORATION, a Missouri
corporation, CAPE COMPOSITES, INC., a California corporation, ENGINEERING
TECHNOLOGY CORPORATION, a Missouri corporation, and ZOLTEK PROPERTIES, INC.,
a Missouri corporation, (individually and collectively hereinafter
"Borrowers"; all references to "Borrowers" or "Borrower" shall mean each and
all of the Borrowers) and SOUTHWEST BANK OF ST. LOUIS (the "Bank"), with an
office at 13205 Manchester Road, St. Louis, Missouri 63131.

                            W I T N E S S E T H:

         WHEREAS, Bank and Borrowers are parties to that certain Credit
Agreement dated as of May 11, 2001, as amended by that certain First
Amendment to Credit Agreement dated as of February 13, 2003 (as amended, the
"Agreement"); and

         WHEREAS, Bank and Borrowers desire to amend the Agreement upon and
subject to the terms and conditions hereinafter set forth.

         NOW, THEREFORE, in consideration of the premises, the covenants,
promises and agreements hereinafter set forth, and other good and valuable
consideration, the receipt and sufficiency of which hereby is acknowledged,
the parties hereto agree as follows:

         1. Amendments to the Agreement.
            ---------------------------

                  (a) Section 3.02 of the Agreement is hereby deleted in its
                      ------------
         entirety and replaced by the following:

                           3.02 TERM OF REVOLVING CREDIT FACILITY. Subject
                                ---------------------------------
                  to the Bank's right to cease making Loans to the Borrowers
                  at any time upon or after the occurrence and during the
                  continuation of any Default or Event of Default, the
                  Borrowers shall be entitled to request advances under the
                  Revolving Credit Note for the period from the date hereof
                  to and including January 31, 2005. In no event may the
                  Borrowers terminate this Agreement until the Borrowers
                  have repaid all Loans and otherwise paid and performed
                  their Obligations hereunder. All indemnities given by the
                  Borrowers to the Bank under any of the Loan Documents
                  shall survive the repayment of the Loans and the
                  termination of this Agreement.

                  (b) Section 3.03(a) of the Agreement is hereby deleted in
                      ---------------
         its entirety and replaced by the following:

                                    (a) Principal payable on account of the
                           Revolving Credit Loan shall be payable by the
                           Borrowers to the Bank immediately upon the
                           earliest to occur of (i) the date or dates for
                           payment as specified in the Revolving Credit
                           Note, (ii) the occurrence of any event described
                           in Section 3.04 hereof which requires the payment
                              ------------
                           of principal on the Loans (but only after the
                           Term Loan has been repaid in full), (iii) the
                           occurrence and continuance of an Event of Default
                           in consequence of which the Bank elects to
                           accelerate the maturity and payment of

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                           any of the Obligations, (iv) termination of this
                           Agreement for any reason, or (v) January 31, 2005
                           (the "Revolving Loan Maturity Date"); provided,
                           however, that if the principal balance of
                           Revolving Credit Loan outstanding at any time
                           shall exceed the Borrowing Base at such time, the
                           Borrowers shall, on demand, repay the Revolving
                           Credit Loan in an amount sufficient to reduce the
                           aggregate unpaid principal amount of such
                           Revolving Credit Loans by an amount equal to such
                           excess;

         2. Conditions To Execution Of This Amendment. Any provision
            -----------------------------------------
contained herein or in the Agreement to the contrary notwithstanding, Bank's
execution of this Amendment is subject to the following:

                  (a) Bank shall have first received a certified copy of the
         resolutions of each Borrower, duly adopted and authorizing the
         execution, delivery and performance of this Amendment in accordance
         with its terms;

                  (b) All representations and warranties made in the
         Agreement and herein shall be true and correct in all material
         respects as of the date hereof and, by execution of this Amendment,
         each Borrower hereby certifies same to Bank;

                  (c) After giving effect to this Amendment, no Borrower
         shall have defaulted, or taken or failed to take any action which,
         unless corrected, would give rise to a default on any of its
         obligations to Bank;

                  (d) After giving effect to this Amendment, no action or
         omission exists as of the date hereof which constitutes, or which,
         with the passage of time, would constitute a Default or Event of
         Default, and each Borrower shall have certified the same to Bank by
         a duly authorized officer;

                  (e) Each Borrower shall be in compliance with all
         covenants of the Agreement, as amended;

                  (f) All documents and filings necessary to maintain and
         perfect Bank's security interest in the collateral provided for in
         the Loan Documents shall be in full force and effect, and all
         actions necessary to maintain and perfect the same shall have
         been taken;

                  (g) No material adverse change in the financial condition
         of the Borrowers taken as a whole shall have occurred since June
         30, 2003;

                  (h) Bank shall have received the following documents, duly
         executed and delivered by all parties thereto, and otherwise
         reasonably satisfactory in form and content to Bank and its
         counsel:

                           (i)      An Amended and Restated Revolving Credit
                                    Note in the form of Exhibit A attached
                                                        ---------
                                    hereto (which shall also serve as the
                                    revised Exhibit A of the Agreement);
                                            ---------

                           (ii)     A photocopy of a fully executed original
                                    of the Securities Purchase Agreement
                                    dated as of December 19, 2003 (as same
                                    may have been amended, the "Securities
                                    Purchase Agreement") by and among Parent
                                    and the Investors (as defined therein);
                                    and

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                           (iii)    A good standing certificate from the
                                    Secretary of State for the
                                    organizational State of each Borrower.

                  (i) The following events shall have occurred or shall
         occur contemporaneously with the closing of the transactions
         contemplated herein:

                           (i)      In addition to, and not in lieu of, any
                                    regularly scheduled principal payments
                                    on same, Bank shall have received a
                                    principal payment of not less than
                                    $2,000,000.00 with respect to that
                                    certain Amended and Restated Term Loan
                                    Note dated as of February 13, 2003 in
                                    the original principal amount of
                                    $3,500,000.00;

                           (ii)     Any and all indebtedness due Bank under
                                    that certain Promissory Note dated
                                    August 12, 1997 in the original
                                    principal amount of $2,407,345.19 and
                                    executed by Zoltek Properties, Inc. in
                                    favor of Bank shall have been paid in
                                    full;

                           (iii)    Any and all amounts due Bank or
                                    otherwise remaining to be paid to Bank
                                    under that certain Master Equipment
                                    Lease dated as of January 1, 1999 (as
                                    same may have been amended, the "Abilene
                                    Lease") by and between the Borrowers and
                                    Bank shall be paid in full. As of
                                    January 9, 2004, the amount to be paid
                                    to Bank to complete or otherwise fulfill
                                    the Borrowers' lease payment obligations
                                    under the Abilene Lease is
                                    $1,839,137.66, with per diem interest in
                                    the amount of $272.85.

                           (iv)     Bank shall have received evidence
                                    satisfactory to Bank that Parent has
                                    received (i) an amount not less than
                                    $7,000,000.00 in connection with the
                                    sale of the Debentures described in the
                                    Securities Purchase Agreement, and (ii)
                                                                   ---
                                    advanced funds in a principal amount not
                                    less than $5,000,000.00 under a credit
                                    facility between the Borrowers and Beal
                                    Bank; and

                           (v)      Bank shall have received evidence
                                    satisfactory to the Bank that Parent has
                                    repaid the borrowings by Parent from
                                    Zsolt Rumy in the amount of
                                    $1,400,000.00 and secured the release of
                                    the letter of credit posted by Zsolt
                                    Rumy for the benefit of Parent in the
                                    amount of $1,400,000.00.

                  (j) No pending or threatened litigation or other
         proceeding or investigation shall exist which could reasonably be
         expected to have a material adverse effect on the prospects,
         operation or financial condition of the Borrowers taken as a whole;
         and

                  (k) The Borrowers shall pay the costs and expenses of Bank
         (including reasonable attorneys' fees and expenses) in connection
         with the negotiation, preparation, execution and delivery of this
         Amendment and all other matters herein provided for or required in
         connection with this Amendment.

         3. Bank Waivers and Consents. Bank agrees to the following waivers
            -------------------------
and consents:

                  (a) Bank hereby waives compliance with the financial
         covenants contained in Section 6.03(a) (Minimum Working Capital),
                                ---------------
         Section 6.03(b) (Debt Coverage Ratio), and Section 6.03(c) (Current
         ---------------                            ---------------
         Ratio) of the Agreement. Such waiver shall be effective from and
         including September

<PAGE>
<PAGE>

         30, 2003 through all covenant testing dates prior to March 31,
         2005. The Borrowers shall be in compliance with such financial
         covenants when tested on March 31, 2005.

                  (b) Notwithstanding any prohibitions contained in the
         Agreement to the contrary, Bank hereby consents to, and waives any
         Default or Event of Default caused by, the following actions taken,
         or to be taken, by the Borrowers:

                           (i)      The sale and issuance of the Debentures
                                    described in the Securities Purchase
                                    Agreement;

                           (ii)     The establishment of, and borrowing
                                    under, a credit facility with Beal Bank
                                    in the approximate principal amount of
                                    $6,000,000.00 and the accompanying liens
                                    granted to Beal Bank with respect to (i)
                                    the real property (including the
                                    improvements and fixtures thereon) of
                                    Borrowers' located at 3101 McKelvey
                                    Road, St. Louis, Missouri, 11 Missouri
                                    Research Park, St. Charles, Missouri and
                                    1221 Fulwiler Road, Abilene, Texas, and
                                    (ii) the personal property which is the
                                    subject of the Abilene Lease; and

                           (iii)    The borrowing of funds by Parent in the
                                    aggregate amount of $2,800,000.00 from
                                    Zsolt Rumy, which borrowings are in the
                                    form of cash borrowings in the amount of
                                    $1,400,000.00 and a standby letter of
                                    credit in the amount of $1,400,000.00
                                    posted for the Parent's benefit.

         4. Representations and Warranties. The Borrowers hereby represent
            ------------------------------
and warrant to Bank that:

                  (a) All representations and warranties made by the
         Borrowers in the Agreement are true and correct in all material
         respects as if they had been made on the date hereof.

                  (b) No Default or Event of Default exists within the
         meaning of the Agreement.

                  (c) The officers of the Borrowers executing this Amendment
         shall be fully authorized to do so, and all corporate actions
         necessary or proper to authorize the execution of this Amendment
         have been duly done, taken and performed. No consent, authorization
         or approval of any other Person is necessary for the due execution
         and delivery by any Borrower of this Amendment and the performance
         by any Borrower of the terms hereof and thereof. This Amendment is
         executed and delivered in accordance with any laws and regulations
         applicable hereto and thereto, and is the legal, valid and binding
         obligation of each Borrower, enforceable in accordance with its
         terms.

                  (d) The execution, delivery, and performance, in
         accordance with its terms, of this Amendment will not violate any
         provision of any Borrower's organizational documents, any law, or
         any applicable judgment or regulation of any court or of any public
         or governmental agency, officer, or authority, and will not
         conflict with, result in a breach of or default under, or result in
         the creation of any lien, charge or encumbrance upon any of the
         property or assets of any Borrower (except for the security
         interest created by the Loan Documents) under any indenture,
         mortgage, contract, deed of trust, or other agreement to which any
         Borrower is a party or by which any Borrower or any of its
         properties or assets is or may be bound.

         5. Entire Agreement. This Amendment and the Agreement embody the
            ----------------
entire agreement between the parties respecting the subject matter hereof
and supersede all prior agreements, proposals,

<PAGE>
<PAGE>

communications and understandings relating to such subject matter. The terms
of the Amendment shall be considered a part of the Agreement as if fully set
forth therein.

         6. Miscellaneous. This Amendment shall be binding upon the
            -------------
Borrowers and their respective successors and the Bank and its successors
and assigns. The Section headings are furnished for the convenience of the
parties and are not to be considered in the construction or interpretation
of this Amendment or the Agreement. This Amendment may be executed in any
number of counterparts, each of which shall be deemed an original, but which
together shall constitute one and the same instrument. Capitalized terms not
defined herein shall have the meanings set forth in the Agreement. This
Agreement shall be a contract made under and governed by the laws of the
State of Missouri applicable to contracts made and to be performed entirely
within such State.

         7. No Other Amendments. In case of a conflict between the terms of
            -------------------
this Amendment and the Agreement, the terms of this Amendment control.
Except as expressly set forth in this Amendment, the terms of the Agreement
remain unchanged and in full force and effect. The following notice is given
pursuant to Section 432.045 of the Missouri Revised Statutes; nothing
contained in such notice shall be deemed to limit or modify the terms of the
Loan Documents:

ORAL AGREEMENTS OR COMMITMENTS TO LOAN MONEY, EXTEND CREDIT OR TO FORBEAR
FROM ENFORCING REPAYMENT OF A DEBT INCLUDING PROMISES TO EXTEND OR RENEW
SUCH DEBT ARE NOT ENFORCEABLE. TO PROTECT YOU (BORROWERS) AND US (BANK) FROM
MISUNDERSTANDING OR DISAPPOINTMENT, ANY AGREEMENTS WE REACH COVERING SUCH
MATTERS ARE CONTAINED IN THIS WRITING, WHICH IS THE COMPLETE AND EXCLUSIVE
STATEMENT OF THE AGREEMENT BETWEEN US, EXCEPT AS WE MAY LATER AGREE IN
WRITING TO MODIFY IT.

                          [SIGNATURE PAGE FOLLOWS]

<PAGE>
<PAGE>

IN WITNESS WHEREOF, the parties have executed this Amendment as of the day
and year first above written.

                                  BORROWERS:

                                  ZOLTEK COMPANIES, INC.

                                  By: /s/ Zsolt Rumy
                                     -----------------------------------------
                                  Name: Zsolt Rumy
                                       ---------------------------------------
                                  Title: President
                                        --------------------------------------

                                  ZOLTEK CORPORATION

                                  By: /s/ Zsolt Rumy
                                     -----------------------------------------
                                  Name: Zsolt Rumy
                                       ---------------------------------------
                                  Title: President
                                        --------------------------------------

                                  CAPE COMPOSITES, INC.

                                  By: /s/ Zsolt Rumy
                                     -----------------------------------------
                                  Name: Zsolt Rumy
                                       ---------------------------------------
                                  Title: President
                                        --------------------------------------

                                  ENGINEERING TECHNOLOGY CORPORATION

                                  By: /s/ Zsolt Rumy
                                     -----------------------------------------
                                  Name: Zsolt Rumy
                                       ---------------------------------------
                                  Title: President
                                        --------------------------------------

                                  ZOLTEK PROPERTIES, INC.

                                  By: /s/ Zsolt Rumy
                                     -----------------------------------------
                                  Name: Zsolt Rumy
                                       ---------------------------------------
                                  Title: President
                                        --------------------------------------

                                  BANK:

                                  SOUTHWEST BANK OF ST. LOUIS

                                  By: /s/ John D. Haffemkeffer
                                     -----------------------------------------
                                  Name: John D. Haffemkeffer
                                       ---------------------------------------
                                  Title: EVP
                                        --------------------------------------

<PAGE>
<PAGE>

                                  EXHIBIT A
                                  ---------

                 AMENDED AND RESTATED REVOLVING CREDIT NOTE
                 ------------------------------------------

US $5,000,000.00                                            January 13, 2004
                                                         St. Louis, Missouri

         For value received, the undersigned, Zoltek Companies, Inc., a
Missouri corporation, Zoltek Corporation, a Missouri corporation, Zoltek
Properties, Inc., a Missouri corporation, Engineering Technology
Corporation, a Missouri corporation and Cape Composites, Inc., a California
corporation (individually and collectively hereinafter "Borrowers"; all
references to "Borrowers" or "Borrower" shall mean each and all of the
Borrowers), hereby jointly and severally promise to pay to the order of
Southwest Bank of St. Louis (the "Bank"), in lawful money of the United
States of America, the principal sum of Five Million Dollars
($5,000,000.00), or if less, the amount outstanding under Section 2.02 of
                                                          ------------
the Credit Agreement (as hereinafter defined), together with interest from
the date hereof at the rate provided for in the Credit Agreement. Principal
and interest of this Note shall be payable at the time or times provided in
Section 3 of the Credit Agreement.
---------

         This Amended and Restated Revolving Credit Note (this "Note") is
the Revolving Credit Note referred to in, and is issued pursuant to, that
certain Credit Agreement among the Borrowers, Hardcore Composites
Operations, LLC and the Bank dated as of May 11, 2001, as amended by that
certain First Amendment to Credit Agreement dated as of February 13, 2003,
and that certain Second Amendment to Credit Agreement of even date herewith
(as further amended or otherwise modified from time to time, the "Credit
Agreement"), and is entitled to all of the benefits and security of the
Credit Agreement. All of the terms, covenants and conditions of the Credit
Agreement and all other instruments evidencing or securing the indebtedness
hereunder are hereby made a part of this Note and are deemed incorporated
herein in full. All capitalized terms used herein, unless otherwise
specifically defined in this Note, shall have the meanings ascribed to them
in the Credit Agreement.

         This Note is secured by the Collateral described in the Credit
Agreement.

         Interest hereunder shall be computed on, the basis of actual days
elapsed over the period of a 360-day year. Upon or after the occurrence and
during the continuation of any Event of Default, the outstanding principal
balance of this Note shall bear interest at a variable rate per annum equal
to the Default Rate until the principal balance of this Note is paid in
full.

         In no contingency or event whatsoever, whether by reason of
advancement of the proceeds hereof or otherwise, shall the amount paid or
agreed to be paid to the Bank for the use, forbearance or detention of money
advanced hereunder exceed the highest lawful rate permissible under any law
which a court of competent jurisdiction may deem applicable hereto.

         The Borrowers may prepay this Note, in whole or in part, at any
time without premium or penalty.

         The termination of the Credit Agreement or the occurrence and
continuance of an Event of Default shall entitle the Bank, at its option, to
declare the then outstanding principal balance and accrued interest hereon
to be, and the same shall thereupon become, immediately due and payable
without notice to or demand upon the Borrowers, all of which the Borrowers
hereby expressly waive.

<PAGE>
<PAGE>

         Time is of the essence of this Note. To the fullest extent
permitted by applicable law, the Borrowers, for themselves and their
successors and assigns, expressly waive presentment, demand, protest and
notice of dishonor, and hereby consent to any extensions of time, renewals,
release of any parties to or guarantors of this Note, waivers and any other
modifications that may be granted or consented to by the Bank from time to
time in respect of the time of payment or any other provision of this Note.

         Wherever possible each provision of this Note shall be interpreted
in such a manner as to be effective and valid under applicable law, but if
any provision of this Note shall be prohibited or invalid under applicable
law, such provision shall be ineffective to the extent of such prohibition
or invalidity without invalidating the remainder of such provision or
remaining provisions of this Note. No delay or failure on the part of the
Bank in the exercise of any right or remedy hereunder shall operate as a
waiver thereof, nor as an acquiescence in any default, nor shall any single
or partial exercise by the Bank of any right or remedy preclude any other
right, or remedy. The Bank, at its option, may enforce its rights against
any collateral securing this Note without enforcing its rights against the
Borrowers, any guarantor of the indebtedness evidenced hereby or any other
property or indebtedness due or to become due to the Borrowers. The
Borrowers agree that, without releasing or impairing the Borrowers'
liability hereunder, the Bank may at any time release, surrender, substitute
or exchange any collateral securing this Note and may at any time release
any party primarily or secondarily liable for the indebtedness evidenced by
this Note.

         This Note is a restated and amended version of that certain Amended
and Restated Revolving Credit Note dated as of February 13, 2003, executed
by Borrowers in favor of Bank in the original principal amount of
$5,000,000.00, and shall not constitute a cancellation of the principal
amount of such note evidenced thereby.

         This Note shall be governed by, and construed and enforced in
accordance with, the internal laws of the State of Missouri.

         BORROWERS HEREBY WAIVE ANY RIGHT TO TRIAL BY JURY (WHICH BANK ALSO
WAIVES) IN ANY ACTION, SUITE, PROCEEDING OR COUNTERCLAIM OF ANY KIND ARISING
OUT OF OR RELATING TO THIS NOTE OR ANY OF THE LOAN DOCUMENTS, THE
COLLATERAL, OR BANK'S CONDUCT IN RESPECT OF ANY OF THE FOREGOING.

         IN WITNESS WHEREOF, the Borrowers have caused this Note to be
executed and delivered by their respective duly authorized representatives
as of the date first above written.

                                  ZOLTEK COMPANIES, INC.

                                  By:
                                     -----------------------------------------
                                  Name:
                                       ---------------------------------------
                                  Title:
                                        --------------------------------------

                                  ZOLTEK CORPORATION

                                  By:
                                     -----------------------------------------
                                  Name:
                                       ---------------------------------------
                                  Title:
                                        --------------------------------------

                                     2

<PAGE>
<PAGE>

                                  ZOLTEK PROPERTIES, INC.

                                  By:
                                     -----------------------------------------
                                  Name:
                                       ---------------------------------------
                                  Title:
                                        --------------------------------------

                                  ENGINEERING TECHNOLOGY CORPORATION

                                  By:
                                     -----------------------------------------
                                  Name:
                                       ---------------------------------------
                                  Title:
                                        --------------------------------------

                                  CAPE COMPOSITES, INC.

                                  By:
                                     -----------------------------------------
                                  Name:
                                       ---------------------------------------
                                  Title:
                                        --------------------------------------

                                     3

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