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                                                                    EXHIBIT 10.1

                       FIRST AMENDMENT TO CREDIT AGREEMENT

      This FIRST AMENDMENT TO CREDIT AGREEMENT (this "Amendment") is dated as of
March 16, 2005, between INSITUFORM TECHNOLOGIES, INC., a Delaware corporation
("Borrower"), and BANK OF AMERICA, N.A., a national banking association
("Lender").

      WHEREAS, the Borrower and the Lender are parties to that certain Amended
and Restated Credit Agreement dated as of March 12, 2004 (the "Original Credit
Agreement")(the Original Credit Agreement, as amended by this Amendment is
referred to herein as the "Credit Agreement");

      WHEREAS, the Borrower has requested that the Lender waive compliance with
certain provisions of the Original Credit Agreement, consent to certain
amendments to the Note Purchase Agreement-1997 and the Note Purchase
Agreement-2003, and consent to certain other transactions as more fully
described herein; and

      WHEREAS, the Lender is willing to accede to such requests in reliance upon
and in accordance with the terms, conditions, representations and warranties set
forth in this Amendment.

      NOW THEREFORE, in consideration of the mutual agreements herein and other
sufficient consideration, the receipt of which is hereby acknowledged, the
Borrower and the Lender hereby agree as follows:

      1.    DEFINITIONS. Unless otherwise specifically defined herein, each term
used herein which is defined in the Original Credit Agreement shall have the
meaning assigned to such term in the Original Credit Agreement. Each reference
to "hereof", "hereunder", "herein" and "hereby" and each other similar reference
and each reference to "this Agreement" and each other similar reference
contained in the Original Credit Agreement shall from the date hereof refer to
the Credit Agreement as amended hereby.

      2.    EFFECTIVENESS OF AGREEMENT. The effectiveness of this Amendment is
subject to the satisfaction and occurrence of the following conditions
precedent:

            (a)   The Lender shall have received the following documents in form
and substance satisfactory to the Lender:

                  (i)   Executed counterparts of this Amendment;

                  (ii)  Executed copies of a consent to this Amendment duly
      executed by each Guarantor party to the Master Guaranty;

                  (iii) The Fifth Amendment dated as of the date hereof to the
      Note Purchase Agreement-1997 (the "1997 NPA Amendment") and the Second
      Amendment dated as of the date hereof to the Note Purchase Agreement-2003
      (the "2003 NPA Amendment"), duly executed and delivered by the Borrower
      and the requisite noteholders thereunder needed to approve such amendments
      and such agreements shall be in form and substance satisfactory to the
      Lender;

                  (iv)  Copies of (a) the resolutions of the Borrower approving
      and authorizing the 1997 NPA Amendment and the 2003 NPA Amendment,
      certified by the Secretary or Assistant Secretary of the Borrower, and (b)
      any other certificates, documents, consents or

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      opinions delivered by any Borrower Party in connection with the 1997 NPA
      Amendment and the 2003 NPA Amendment; and

                  (v)   Such other assurances, certificates, documents, consents
      or opinions as the Lender reasonably may require.

            (b)   The Lender shall have received payment from Borrower of the
amendment fee set forth in that certain fee letter dated as of the date hereof
among the Borrower and the Lender.

            (c)   The Borrower shall have paid the fees, costs and expenses of
Bryan Cave LLP, special counsel to the Lender, incurred in connection with the
consummation of the transactions contemplated by this Amendment.

      3.    AMENDMENTS TO CREDIT AGREEMENT. Subject to the terms and conditions
set forth in Section 2 hereof, the Credit Agreement is hereby amended as
follows:

            (a)   The defined term "Maturity Date" in Section 1.01 of the Credit
      Agreement is amended by replacing the date "September 12, 2005" with
      "March 31, 2006".

            (b)   The defined term "Note Purchase Agreement-1997" in Section
      1.01 of the Credit Agreement is amended and restated in its entirety as
      follows:

            "Note Purchase Agreement-1997" means the Note Purchase Agreement
            dated as of February 14, 1997, as amended to and including March 15,
            2005, among Company and other parties signatory thereto under which
            Company issued certain 7.88% Senior Notes, Series A, due February
            14, 2007, of $110,000,000 aggregate principal amount; provided,
            however, that, except with respect to Section 8.01(f) of this
            Agreement (which is a cross default to other Indebtedness, including
            the Note Purchase Agreement-1997 as in effect from time to time),
            after March 15, 2005, no amendments to, or waivers of, the terms,
            conditions and definitions of the Note Purchase Agreement-1997
            referred to or incorporated by reference herein shall be deemed to
            amend or waive such terms, conditions and definitions for purposes
            of this Agreement unless Lender separately agrees or consents
            thereto hereunder. The terms, conditions and definitions referred to
            or incorporated by reference herein will survive termination,
            restatement or cancellation of the Note Purchase Agreement-1997 for
            purposes of this Agreement (other than Section 8.01(f)).

            (c)   The defined term "Note Purchase Agreement-2003" in Section
      1.01 of the Credit Agreement is amended and restated in its entirety as
      follows:

            "Note Purchase Agreement-2003" means the Note Purchase Agreement
            dated as of April 24, 2003, as amended to and including March 15,
            2005, among Company and other parties signatory thereto under which
            Company issued certain 5.29% Senior Notes, Series 2003-A, due April
            24, 2013, of $65,000,000 aggregate principal amount; provided,
            however, that, except with respect to Section 8.01(f) of this
            Agreement (which is a cross default to other Indebtedness, including
            the Note Purchase Agreement-2003 as in effect from time to time),
            after March 15, 2005, no amendments to, or waivers of, the terms,
            conditions and definitions of the Note Purchase Agreement-2003
            referred to or incorporated by reference herein shall be deemed to
            amend or waive such terms, conditions and

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            definitions for purposes of this Agreement unless Lender separately
            agrees or consents thereto hereunder. The terms, conditions and
            definitions referred to or incorporated by reference herein will
            survive termination, restatement or cancellation of the Note
            Purchase Agreement-2003 for purposes of this Agreement (other than
            Section 8.01(f)).

            (d)   Section 1.01 of the Credit Agreement is amended by adding the
      following defined term:

            "Unrestricted Cash Balance" means as of any date of determination
            for the Borrower and its Subsidiaries on a consolidated basis, an
            amount equal to the sum of cash and cash equivalents (excluding any
            restricted cash balances or other retainage deposits), determined in
            accordance with GAAP.

            (e)   Section 2.03(j) of the Credit Agreement is amended by
      replacing the phrase "two and one-fourth percent (2.25%)" with the phrase
      "two and one-half percent (2.50%)".

            (f)   Section 2.08(a) of the Credit Agreement is amended by
      replacing the phrase "four-tenths of one percent (0.40%)" with the phrase
      "one-half of one percent (0.50%)".

            (g)   Section 7 of the Credit Agreement is amended by adding the
      following subsection at the end thereof:

            "7.05 MINIMUM CASH BALANCE. Permit, at any time, the Unrestricted
            Cash Balance to be less than $50,000,000 (or its equivalent in any
            other currency or currencies)."

            (h)   Exhibit B to the Credit Agreement is replaced in its entirety
      with Annex A attached hereto.

      4.    WAIVERS AND CONSENTS.

            (a)   Borrower has notified Lender that Borrower has violated
Section 10.2 (Fixed Charges Coverage Ratio) of the Note Purchase Agreement-1997
for the December 31, 2004 calculation date, which has given rise to an Event of
Default under Section 8.01(f) of the Credit Agreement (the "Covenant Default").
Borrower has requested that the Lender waive the Covenant Default, and the
Lender hereby waives the Covenant Default.

            (b)   Borrower has notified the Lender that Insituform Technologies
Limited, a foreign Subsidiary of the Borrower which is incorporated in England
and Wales ("ITL"), entered into a joint venture agreement with Environmental
Techniques Limited, a Northern Ireland company ("ETL") during calendar year
2004, pursuant to which ITL and ETL agreed to form Insituform Environmental
Techniques Limited, a Northern Ireland company ("IETL"), for the purpose of
promoting, marketing and distributing trenchless inspection, repair and
installation services in Northern Ireland and the Republic of Ireland. ITL has
entered into a subscription agreement for the purchase of 49.9% of the share
capital of IETL for (pound)499 (the "IETL Shares"). The Lender hereby waives
compliance with Section 7.01 of the Credit Agreement solely to the extent
necessary to waive any Default or Event of Default arising out of or relating to
the Borrower's subscription to purchase the IETL Shares, and the Lender hereby
consents to the purchase of

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the IETL Shares by the Borrower pursuant to the subscription agreement provided
that the consideration for such purchase shall not exceed (pound)499.

            (c)   Subject to the terms and conditions set forth herein, the
Lender hereby consents to the execution and delivery by the Borrower of the 1997
NPA Amendment and the 2003 NPA Amendment.

            (d)   The waivers and consents contained in this Section 4 are
specific in intent and are valid only for the specific purpose for which given.
Nothing contained herein obligates the Lender to agree to any additional waivers
of or consents to any provisions of any of the Loan Documents. The waivers
contained in this Section 4 are waivers of those items set forth in subsections
(a) and (b) of this Section 4 only and shall not operate as a waiver of Lender's
right to exercise remedies resulting from (i) existing and/or continuing
Defaults or Events of Default of which Lender is not actually aware, or (ii)
other future Defaults or Events of Default, whether or not of a similar nature
and whether or not known to Lender.

      5.    NOTICE ADDRESS. The notice address of the Lender for purposes of
Section 10.02 of the Credit Agreement shall be as follows:

            Bank of America, N.A.
            MO1-800-12-01
            800 N. Market Street, 12th Floor
            St. Louis, MO 63101
            Attention: Jason R. Hickey
                       Senior Vice President
            Telephone: (314) 466-6811
            Facsimile: (314) 466-6499
            Email: jason.hickey@bankofamerica.com

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            With a copy to:

            Harold R. Burroughs, Esq.
            Bart D. Wall, Esq.
            Bryan Cave LLP
            One Metropolitan Square, Suite 3600
            St. Louis, Missouri 63102-2750
            Telephone: (314) 259-2000
            Facsimile: (314) 259-2020
            Email: hrburroughs@bryancave.com
                   bdwall@bryancave.com

      6.    REPRESENTATIONS AND WARRANTIES OF BORROWER. Borrower hereby
represents and warrants to the Lender that (i) the Borrower's execution of this
Amendment has been duly authorized by all requisite action of the Borrower; (ii)
no consents are necessary from any third parties for the Borrower's execution,
delivery or performance of this Amendment, (iii) each of this Amendment, the
Credit Agreement and any other Loan Documents to which a Borrower Party is a
party constitute the legal, valid and binding obligations of such Borrower
Party, enforceable against such Borrower Party in accordance with its terms,
except to the extent that the enforceability thereof against such Borrower Party
may be limited by bankruptcy, insolvency or other laws affecting the
enforceability of creditors rights generally or by equity principles of general
application, (iv) the representations and warranties of the Borrower contained
in Section 5 of the Credit Agreement are true and correct in all material
respects on and as of the date hereof as if such representations and warranties
had been made on and as of the date hereof, except to the extent such
representations and warranties expressly relate to an earlier date, and (v)
after giving effect to this Amendment, there is no Default or Event of Default
under the Credit Agreement.

      7.    GOVERNING LAW. This Amendment shall be governed by, and construed in
accordance with, the law of the State of Missouri applicable to agreements made
and to be performed entirely within such state; provided that Lender shall
retain all rights arising under Federal law.

      8.    SECTION TITLES. The section titles in this Amendment are for
convenience of reference only and shall not be construed so as to modify any
provisions of this Amendment.

      9.    COUNTERPARTS; FACSIMILE TRANSMISSIONS. This Amendment may be
executed in one or more counterparts and on separate counterparts, each of which
shall be deemed an original, but all of which together shall constitute one and
the same instrument. Signatures to this Amendment may be given by facsimile or
other electronic transmission, and such signatures shall be fully binding on the
party sending the same.

      10.   STATUTORY NOTICE - ORAL COMMITMENTS. Nothing contained in the
following 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 (BORROWER) AND US (CREDITOR)
      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.

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         11. POST-CLOSING ACTION. Notwithstanding anything to the contrary set
forth herein, the Borrower covenants and agrees to deliver to the Lender a copy
of the resolutions of the Board of Directors of Borrower, duly adopted, which
authorize and ratify the execution, delivery and performance of this Amendment
and the other documents executed pursuant to or in connection with this
Amendment, certified by the Secretary or Assistant Secretary of the Borrower.
Borrower agrees that the failure by Borrower to deliver such resolutions to
Lender on or before March 31, 2005 shall constitute an Event of Default under
the Credit Agreement and each of the other Loan Documents and the obligation of
the Lender to make additional Loans or issue Letters of Credit shall terminate
without any further action by the Lender.

            [The remainder of this page is intentionally left blank.]

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      IN WITNESS WHEREOF, this Amendment has been duly executed as of the date
first above written.

                                    INSITUFORM TECHNOLOGIES, INC.

                                    By: /s/ Christian G. Farman
                                        --------------------------------------
                                        Christian G. Farman
                                        Senior Vice President, Chief Financial
                                        Officer and Assistant Secretary

                                    BANK OF AMERICA, N.A.

                                    By: /s/ Jason R. Hickey
                                        --------------------------------------
                                        Jason R. Hickey
                                        Senior Vice President