In its May 8, 2008 report, RiskMetrics said:

"Regarding Water Asset Management, we note that it is a new fund with no publicly available track record of creating shareholder value through active board participation." *

RiskMetrics also stated that:

"[We] believe that the dissidents' emphasis on selling the company without hiring a CEO may not have been appropriate. Shareholders have benefited by the board's decision to pursue the strategic plan under a new CEO. We note that the company's share price increased by 26.6 percent between Dec. 7, 2007 (the date dissidents sent their letter to the board) and April 25, 2008 (announcement of dissidents operating plan), compared to a decline of 19.23 percent in North America DS Water Index and 10.60 percent in S&P World Water Index, during the same period."*

RiskMetrics further noted that:

"[We] note that the company's stock price has increased by 20.8 percent since Joe Burgess
assumed the CEO position, compared to the 4.6 percent increase in Water Index during the same period. Our review of analyst reports and the increase in company's stock price since Joe Burgess took over, suggests that the market generally likes the incumbent board's plan." *

RiskMetrics concluded:

"…the dissidents have not met its burden of proving it is better able to increase value than the incumbent board. As such, given that the company's strategic plan under the new management has successfully enhanced shareholder value; the dissidents' focus has primarily been on selling the company until very recently; the lack of dissident nominees water-related operating experience; the lack of a detailed plan by the dissidents; the similarity between the dissidents proposed plan and the plan being implemented by the company, we recommend that shareholders vote on the WHITE ballot and vote FOR all management nominees." *

J. Joseph "Joe" Burgess, Insituform's President and Chief Executive Officer, said, "We are pleased that RiskMetrics supports the election of Insituform's directors.  The RiskMetrics recommendation reaffirms our belief that we have the right Board in place as we continue to execute the Company's strategic plan to drive sustainable and profitable growth.  We strongly urge all Insituform stockholders to vote FOR Insituform's Board nominees on the WHITE proxy card and reject the Water Asset Management nominees. We look forward to continuing to build a stronger future for Insituform and all of our shareholders."

Stockholders with questions or who need assistance voting their shares may call the Company's proxy solicitor, Innisfree M&A Incorporated, at (888) 750-5834.

* Permission to use quotations was neither sought nor obtained.

About Insituform   
Insituform Technologies, Inc. is a leading worldwide provider of proprietary technologies and services for rehabilitating sewer, water and other underground piping systems without digging and disruption. More information about the Company can be found on its Internet site at www.insituform.com.       

Additional Information   
Insituform has filed a definitive proxy statement with the Securities and Exchange Commission ("SEC") in connection with its 2008 Annual Meeting. Insituform's stockholders are strongly advised to read the definitive proxy statement carefully, as it contains important information.  Free copies of the definitive proxy statement, and any amendments or supplements thereto, and other materials filed by Insituform with the SEC will be available free of charge on the SEC's website at www.sec.gov, on Insituform's website at www.insituform.com under Investors/SEC or by directing requests to Insituform's proxy solicitor, Innisfree M&A Incorporated, toll free at (888) 750-5834.     

Forward-Looking Statements
The Private Securities Litigation Reform Act of 1995 provides a "safe harbor" for forward-looking statements.  The Company makes forward-looking statements in this document that represent the Company's beliefs or expectations about future events or financial performance.  These forward-looking statements are based on information currently available to the Company and on management's beliefs, assumptions, estimates and projections and are not guarantees of future events or results.  When used in this document, the words "anticipate," "estimate," "believe," "plan," "intend," "may," "will" and similar expressions are intended to identify forward-looking statements, but are not the exclusive means of identifying such statements.  Such statements are subject to known and unknown risks, uncertainties and assumptions, including those referred to in the "Risk Factors" section of the Company's Annual Report on Form 10-K for the year ended December 31, 2007, as filed with the Securities and Exchange Commission on March 10, 2008.  In light of these risks, uncertainties and assumptions, the forward-looking events discussed may not occur.  In addition, our actual results may vary materially from those anticipated, estimated, suggested or projected.  Except as required by law, we do not assume a duty to update forward-looking statements, whether as a result of new information, future events or otherwise.  Investors should, however, review additional disclosures made by the Company from time to time in its periodic filings with the Securities and Exchange Commission.  Please use caution and do not place reliance on forward-looking statements.  All forward-looking statements made by the Company in this document are qualified by these cautionary statements.

Insituform®, the Insituform® logo, Insituform Blue®, United Pipeline Systems® and Clean Water for the World® are the registered trademarks of Insituform Technologies, Inc. and its affiliates.

CONTACT:

David A. Martin
Vice President and Chief Financial Officer
Insituform Technologies, Inc.
636-530-8000

Matthew Sherman / Dan Katcher
Joele Frank, Wilkinson Brimmer Katcher
212-355-4449