AS  FILED  WITH  THE  

As filed with the Securities and Exchange Commission on December 15, 2006

Registration No. 333-_____ 

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION ON JANUARY 22, 1998. REGISTRATION NO. 333-______ SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM S-3

REGISTRATION STATEMENT UNDER

THE SECURITIES ACT OF 1933

MFRI, INC. (Exact

(Exact name of registrant as specified in its charter)

DELAWARE

Delaware

36-3922969 (State

(State or other jurisdictiction (IRS Employerjurisdiction of incorporation or organization)

(I.R.S. Employer Identification No.) Number)

7720 LEHIGH AVENUE NILES, ILLINOISLehigh Avenue

Niles, Illinois 60714

(847) 966-1000 (Address,

(Address, including ZIPzip code, and telephone number, including area code, of registrant'sregistrant’s principal executive offices) DAVID UNGER CHAIRMAN OF THE BOARD OF DIRECTORS

Mr. David Unger

Chairman of the Board of Directors

MFRI, INC. Inc.

7720 LEHIGH AVENUE NILES, ILLINOISLehigh Avenue

Niles, Illinois 60714

(847) 966-1000 (Name,

(Name, address, including ZIP Code,zip code, and telephone number, including area code, of agent for service) COPIES TO: HAL

Copy to:

Hal M. BROWN, ESQ. RUDNICK & WOLFE Brown, Esq.

DLA Piper US LLP

203 NORTH LASALLE STREET, SUITE 1800 CHICAGO, ILLINOISNorth LaSalle Street, Suite 1900

Chicago, Illinois 60601

(312) 368-4012 (312) 236-7516(TELECOPIER) APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: FROM TIME TO TIME AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT.

Approximate date of commencement of proposed sale to the public: From time to time after this registration statement becomes effective.

If the only securities being registered on this formForm are being offered pursuant to dividend or interest reinvestment plans, please check the following box. [ ]

If any of the securities being registered on this formForm are beingto be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, other than securities offered only in connection with dividend or interest reinvestment plans, check the following box. [ X ]

If this formForm is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. [ ]

If this formForm is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. [ ]

If delivery ofthis Form is a registration statement pursuant to General Instruction I.D. or a post-effective amendment thereto that shall become effective upon filing with the prospectus is expected to be madeCommission pursuant to Rule 434, please462(e) under the Securities Act, check the following box.
CALCULATION OF REGISTRATION FEE AMOUNT TO PROPOSED MAXIMUM PROPOSED MAXIMUM AMOUNT OF TITLE OF BE REGISTERED AGGREGATE PRICE AGGREGATE REGISTRATION SHARES PER UNIT{(1)} OFFERING PRICE FEE TO BE REGISTERED Common Stock, par value $.01 per share 75,000 $8.13 $609,750 $180.00
(1)Estimated solely for purposes[ ]

If this Form is a post-effective amendment to a registration statement filed pursuant to General Instruction I.D. filed to register additional securities or additional classes of calculatingsecurities pursuant to Rule 413(b) under the Securities Act, check the following box. [ ]

CALCULATION OF REGISTRATION FEE

Title of each class
of securities to be registered

Amount to be registered

Proposed maximum offering price per unit(1)

Proposed maximum aggregate offering price (1)

Amount of registration
fee

Common Stock, par value, $0.01 per share

1,500,000 shs.

$22.02

$33,030,000

$3,535

(1)

Estimated solely for the purpose of computing the registration fee in accordance with Rule 457(c) based on the average of the high and low reported sales prices on the NASDAQ Global Market on December 11, 2006.

The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Rule 457(c) underSection 8(a) of the Securities Act of 1933 basedor until the Registration Statement shall become effective on such date as the averageCommission, acting pursuant to said Section 8(a), may determine.



The information in this prospectus is not complete and may be changed. We may not sell these securities until the registration statement relating to these securities has been declared effective by the Securities and Exchange Commission. This prospectus is neither an offer to sell nor a solicitation of the high and low prices per share of the an offer to buy these securities in any jurisdiction where such offer or sale is unlawful.

Subject to Completion

Dated _______, 2006

PROSPECTUS

1,500,000 Shares

MFRI, INC.

Common Stock reported on the Nasdaq National Market on January 21, 1998. THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A), MAY DETERMINE. INFORMATION CONTAINED HEREIN IS SUBJECT TO COMPLETION OR AMENDMENT. A REGISTRATION STATEMENT RELATING TO THESE SECURITIES HAS BEEN FILED WITH THE SECURITIES AND EXCHANGE COMMISSION. THESE SECURITIES MAY NOT BE SOLD NOR MAY OFFERS TO BUY BE ACCEPTED PRIOR TO THE TIME THE REGISTRATION STATEMENT BECOMES EFFECTIVE. THIS PROSPECTUS SHALL NOT CONSTITUTE AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO BUY NOR SHALL THERE BE ANY SALE OF THESE SECURITIES IN ANY STATE IN WHICH SUCH OFFER, SOLICITATION OR SALE WOULD BE UNLAWFUL PRIOR TO REGISTRATION OR QUALIFICATION UNDER THE SECURITIES LAWS OF ANY SUCH STATE. SUBJECT TO COMPLETION, DATED JANUARY 22, 1998 PROSPECTUS 75,000 Shares MFRI, INC. COMMON STOCK

This Prospectusprospectus relates to 75,000the offer and sale from time to time of 1,500,000 shares ("Shares") of common stock par value $.01 per share (the "Common Stock"), of MFRI, Inc., a Delaware corporation (the "Company"“Company”), which may hereafter be offered or sold from time to time forpar value $0.01 per share (“Common Shares”) by the account of persons namedCompany.

The Common Shares are listed on the NASDAQ Global Market under the caption "Selling Stockholders." symbol “MFRI”.

Investing in our securities involves risk. Before buying our securities, you should read and consider the risk factors included in our periodic reports and in other information that we file with the Securities and Exchange Commission. See “Special Note Regarding Forward-Looking Statements.”

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The Shares may be issued from timedate of this prospectus is ___________, 200_.



TABLE OF CONTENTS

Page

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

3

AVAILABLE INFORMATION

3

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

3

THE COMPANY

4

USE OF PROCEEDS

4

PLAN OF DISTRIBUTION

4

EXPERTS

5

LEGAL MATTERS

5

No dealer, salesperson or other individual has been authorized to time pursuantgive any information or to options issuedmake any representations not contained or incorporated by reference in this prospectus in connection with the purchaseoffering covered by this prospectus. If given or made, such information or representations must not be relied upon as having been authorized by us. This prospectus does not constitute an offer to sell, or a solicitation of TDC Filter Manufacturing, Inc., a Delaware corporation,an offer to buy, the Common Shares, in any jurisdiction where, or to any person to whom, it is unlawful to make any such offer or solicitation. Neither the delivery of this prospectus nor any offer or sale made hereunder shall, under any circumstances, create an implication that there has not been any change in the facts set forth in this prospectus or in our affairs since the date hereof.


SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

Information contained in or incorporated by reference into this prospectus and any accompanying prospectus supplement contains “forward-looking statements” within the meaning of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”). We intend the forward-looking statements to be covered by the Company,safe harbor provisions for forward-looking statements contained in that section. These forward-looking statements relate to, without limitation, our anticipated future economic performance, our plans and objectives for future operations and projections of revenue and other financial items, which occurred on December 3, 1997.can be identified by the use of forward-looking words such as “may,” “will,” “should,” “expect,” “anticipate,” “estimate” or “continue” or the negative thereof or other variations thereon or comparable terms. The Shares may hereafter be offered or sold from time to time for the account of persons namedcautionary statements under the caption "Selling Stockholders"“Risk Factors” contained in our Annual Report on Form 10-K for the Nasdaq National Market,year ended January 31, 2006, which is incorporated herein by reference, and other similar statements contained in this prospectus or otherwise, at pricesany accompanying prospectus supplement identify important factors with respect to forward-looking statements, including certain risks and on terms then obtainable,uncertainties, that could cause actual results to differ materially from those in broker's transactions, special offerings, exchange distributions, negotiated transactions, block transactions, or otherwise. See "Selling Stockholders" and "Plan of Distribution." The Company will not realize any proceeds from any sale of the Shares. The Common Stock is traded on the Nasdaq National Market under the symbol "MFRI." On January 21, 1998, the last reported sale price of the Common Stock on the Nasdaq National Market was $8.13. ______________ THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND EXCHANGE COMMISSION OR ANY STATE SECURITIES COMMISSION NOR HAS THE COMMISSION PASSED OR ANY STATE SECURITIES COMMISSION UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE. ______________ THE DATE OF THIS PROSPECTUS IS ___________, 1998 NO DEALER, BROKER OR OTHER PERSON HAS BEEN AUTHORIZED TO GIVE ANY INFORMATION OR TO MAKE ANY REPRESENTATIONS, OTHER THAN THOSE CONTAINED OR INCORPORATED HEREIN BY REFERENCE IN THIS PROSPECTUS, IN CONNECTION WITH THE OFFERING MADE HEREBY, AND, IF GIVEN OR MADE, SUCH INFORMATION OR REPRESENTATIONS MUST NOT BE RELIED ON AS HAVING BEEN AUTHORIZED BY THE COMPANY OR THE SELLING SHAREHOLDERS. THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL OR A SOLICITATION OF ANY OFFER TO BUY THE SECURITIES TO WHICH IT RELATES IN ANY JURISDICTION IN WHICH, OR TO ANY PERSON TO WHOM, IT IS UNLAWFUL TO MAKE SUCH AN OFFER OR SOLICITATION OF AN OFFER. NEITHER THE DELIVERY OF THIS PROSPECTUS NOR ANY OFFER OR SALE MADE HEREUNDER SHALL, UNDER ANY CIRCUMSTANCES, CREATE ANY IMPLICATION THAT THERE HAS BEEN NO CHANGE IN THE INFORMATION SET FORTH HEREIN OR IN THE AFFAIRS OF THE COMPANY SINCE THE DATE HEREOF. THIS PROSPECTUS, INCLUDING DOCUMENTS INCORPORATED HEREIN BY REFERENCE, CONTAINS FORWARD-LOOKING STATEMENTS WITHIN THE MEANING OF SECTION 27A OF THE SECURITIES ACT AND SECTION 21E OF THE EXCHANGE ACT. FORWARD-LOOKING STATEMENTS ARE INHERENTLY SUBJECT TO RISKS AND UNCERTAINTIES, MANY OF WHICH CANNOT BE PREDICTED WITH ACCURACY AND SOME OF WHICH MIGHT NOT EVEN BE ANTICIPATED. FUTURE EVENTS AND ACTUAL RESULTS, FINANCIAL AND OTHERWISE, MAY DIFFER MATERIALLY FROM THE RESULTS DISCUSSED IN THE FORWARD-LOOKING STATEMENTS. FACTORS THAT MIGHT CAUSE SUCH A DIFFERENCE INCLUDE, BUT ARE NOT LIMITED TO, THOSE DISCUSSED IN "RISK FACTORS" HEREIN AND IN "MANAGEMENT'S DISCUSSION AND ANALYSIS OF RESULTS OF OPERATIONS AND FINANCIAL CONDITION" INCORPORATED BY REFERENCE IN THE COMPANY'S ANNUAL REPORT ON FORM 10-K FOR THE FISCAL YEAR ENDED JANUARY 31, 1997, WHICH IS INCORPORATED BY REFERENCE IN THIS PROSPECTUS. TABLE OF CONTENTS
PAGE AVAILABLE INFORMATION ....................................... 3 RISK FACTORS ................................................ 3 THE COMPANY ................................................. 4 SELLING STOCKHOLDERS ........................................ 6 USE OF PROCEEDS ............................................. 6 PLAN OF DISTRIBUTION ........................................ 6 LEGAL MATTERS ............................................... 7 EXPERTS ..................................................... 7 INFORMATION INCORPORATED BY REFERENCE ....................... 8
such forward-looking statements.

AVAILABLE INFORMATION The Company is

We are subject to the informational requirements of the Securities Exchange Act of 1934, as amended (the "Exchange Act"“Exchange Act”), and, in accordance therewith, files periodicwe are required to file reports, proxy statements and other information with the Securities and Exchange Commission (the "Commission"“Commission”). SuchYou may read and copy these reports, proxy statements and other information can be inspected and copied at the public reference facilities maintained byPublic Reference Room of the Commission, at Room 1024, 450 Fifth100 F Street, N.W.N.E., Washington, D.C. 20549, and should20549. You may also be available for inspection and copying at the regional officesobtain copies of the Commission located at 75 Park Place, 14th Floor, New York, New York 10007 and 500 West Madison Street, Suite 1400, Chicago, Illinois 60661. Copies of such material can also be obtained from the Public Reference Section of the Commission at 450 Fifth Street, N.W., Washington, D.C. 20549 at prescribed rates. The Commission maintains a Web site that contains reports, proxy and information statements and other information aboutregarding issuers that file electronically with the Company. The address ofCommission by accessing the Commission's World Wide Web site maintained by the Commission is "http:at http://www.sec.gov". The Common Stock is tradedwww.sec.gov. You may obtain information on the National Market tieroperation of the Nasdaq Stock Market ("Nasdaq"). Information filed by the Company with Nasdaq may be obtained at 1735 K Street, N.W., Washington, D.C. 20006. This Prospectus constitutes a part of a registration statement on Form S-3 (herein, together with all amendments and exhibits, the "Registration Statement") under the Securities Act of 1933, as amended (the "Securities Act"), filed by the Company. This Prospectus does not contain all of the information set forth in the Registration Statement. For further information, reference is hereby made to the Registration Statement, including the financial schedules and exhibits filed or incorporated by reference as a part thereof, which may be examined at the Public Reference Room by calling the Commission at 1-800-SEC-0330.

INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

We have filed the documents listed below with the Commission under the Exchange Act and these documents are incorporated into this prospectus by reference:

a.

Annual Report on Form 10-K for the year ended January 31, 2006.

b.

Quarterly Reports on Form 10-Q for the periods ended April 30, 2006, July 31, 2006, and October 31, 2006.

c.

Current Reports on Form 8-K filed on April 20, 2006, June 30, 2006, September 21, 2006, October 18, 2006, and November 6, 2006.

d.

Description of our common shares contained in the registration statement of our predecessor on Form 8-A filed on March 13, 1990.

All documents filed by us pursuant to Sections 13(a), 13(c), 14 and 15(d) of the CommissionExchange Act after the date of this prospectus and prior to the termination of the offering of all Common Shares under this prospectus will also be deemed to be incorporated by reference in Washington, D.C., without charge, or copies of which maythis prospectus and to be obtaineda part hereof from the Commission upon paymentdate of filing those documents.

Any statement contained in this prospectus or in a document incorporated or deemed to be incorporated by reference herein will be modified or superseded by inconsistent statements in any document we file in the prescribed fees. Statements containedfuture that will be deemed incorporated by reference herein, concerningincluding any prospectus supplement that supplements this prospectus. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus or any accompanying prospectus supplement. Subject to the provisions of documents filed herewith as exhibits are necessarily summaries of such documents,foregoing, all information appearing in this prospectus and each such statementaccompanying prospectus supplement is qualified in its entirety by reference to the copy of the applicable document filed with the Commission. RISK FACTORS COMPETITION; BUSINESS. The businesses in which the Company is engaged are highly competitive. In addition, new installations of baghouses are subject to competition from alternative technologies, and the sale of specialty piping systems and electronic leak detection and location systems are subject to competition from alternative products. The business of Thermal Care (as defined below) is dependent on the plastics industry. Any adverse trendsinformation appearing in the plastics industry may have a material adverse effect ondocuments incorporated by reference.

We will provide, without charge, copies of all documents that are incorporated herein by reference (not including the business of Thermal Care. Thermal Care relies upon a single source for key components of several of its products. Although the Company believes that thereexhibits to such information, unless such exhibits are alternate sources available for such components, there can be no assurance that the interruption of supplies of such components would not have an adverse effect on the financial condition of the Company, and that the Company, if required to do so, would be able to negotiate agreements with alternative sources on acceptable terms. GOVERNMENT REGULATION. The demand for the Company's leak detection and location systems and secondary containment piping systems is driven primarilyspecifically incorporated by government regulation with respect to hazardous waste. Laws such as the Federal Resource Conservation and Recovery Act, and standards such as the National Emission Standard for Hydrocarbon Airborne Particulates, have increased the demand for the Company's leak detection and location and secondary containment piping systems. The Company's filtration products business to a large extent is dependent on governmental regulation of air pollution at the federal and state levels. The Company believes that continuing growth in the sale of filtration products and services will be materially dependent on continuing enforcement of environmental laws such as the Federal Clean Air Act Amendments of 1990. Although changesreference in such environmental regulations could significantly alterinformation) to each person, including any beneficial owner, to whom this prospectus is delivered upon written or oral request. Requests should be directed to MFRI, Inc., 7720 Lehigh Avenue, Niles, Illinois 60714, Attention: Michael D. Bennett (telephone number: (847) 966-1000.)


Unless otherwise indicated, when used herein, the demand forterms "we, "us," and “our” refer to MFRI, Inc., a Delaware corporation, and its subsidiaries.

THE COMPANY

MFRI, Inc., (“MFRI”), the Company's products and services,(“Company” or the Company does not believe that such a change is likely to decrease demand in the foreseeable future. ECONOMIC FACTORS. Although demand for many of the Company's products is generally affected by its customers' need to comply with governmental regulations, purchases of the Company's products at times may be delayed by customers due to adverse economic factors. DIVIDENDS. The Company has not paid dividends in the past and does not anticipate paying cash dividends on the Common Stock in the foreseeable future. The Company's line of credit agreement contains certain restrictions on payment of dividends. The primary restriction limits dividends to a cumulative amount of up to 25% of net income. THE COMPANY The Company“Registrant”) is engaged in the manufacture and sale of filter bags for useproducts in industrial air pollution control systems known as "baghouses", and also engineers, designs and manufactures specialtythree distinct business segments: filtration products, piping systems and leak detection and location systems, and industrial waterprocess cooling equipment. The Company, which was incorporated in Delaware in October 1993, is the successor corporation to Midwesco Filter Resources, Inc. ("Midwesco Filter"). Midwesco Filter was incorporated in Delaware in October 1989 as a wholly-owned subsidiary of Midwesco, Inc. ("Midwesco"), an Illinois corporation. On December 13, 1989, Midwesco Filter exchanged shares of its common stock for the net assets constituting the Midwesco Filter Resources division ("Filter Division") of Midwesco. The Filter Division was formed from certain assets of the Filter Media division of the Kennecott Corporation, acquired by Midwesco in June 1982, and certain assets of the Filter Resources Corporation, acquired by Midwesco in December 1983. On January 28, 1994 pursuant to a merger transaction ("Perma-Pipe Transaction") between the Company, a subsidiary of the Company and Midwesco Filter, the Company acquired the Perma-Pipe business ("Perma-Pipe") from Midwesco for cash and 278,666 shares of Common Stock. Pursuant to the Perma-Pipe Transaction, each share of common stock of Midwesco Filter was exchanged for one share of Common Stock. Immediately prior to the effective time of the Perma-Pipe Transaction, a public offering (the "Offering") of shares of common stock of Midwesco Filter was consummated, the net proceeds of which were used to repay bank debt related to Perma-Pipe. Perma-Pipe is in the business of engineering, designing and manufacturing specialty piping systems and leak detection and location systems. On September 30, 1994, the Company and an indirect wholly-owned subsidiary of the Company, pursuant to a purchase agreement dated as of such date ("Purchase Agreement"), acquired substantially all of the assets of Ricwil Piping Systems Limited Partnership ("Ricwil LP") for cash and 55,710 shares of Common Stock, as adjusted in accordance with the terms of the Purchase Agreement. Ricwil LP was a manufacturer of insulated piping systems for district heating and cooling systems. On December 6, 1995, Perma-Pipe acquired for cash the net assets and leak detection business of Hagenuk GmbH. On August 15, 1996, the Company, pursuant to an Asset Purchase Agreement dated as of such date (the "Eurotech Agreement"), acquired substantially all of the assets of Eurotech Air Filtration, Inc., an Oregon corporation ("Eurotech"), for cash and 30,571 shares of Common Stock. Pursuant to the Eurotech Agreement, Eurotech distributed such shares to its four shareholders. On December 30, 1996, the Company acquired the Thermal Care Division ("Thermal Care") and certain other specified assets and liabilities of Midwesco by the merger of Midwesco with and into the Company (the "Merger"). Through the Merger, an aggregate of 2,124,298 shares of Common Stock were issued to the shareholders of Midwesco and the 1,717,666 shares of Common Stock owned by Midwesco immediately prior to the consummation of the Merger were cancelled. Thermal Care engineers, designs and manufactures industrial water cooling equipment. On December 3, 1997, the Company and a wholly-owned subsidiary, pursuant to a Stock Purchase Agreement dated as of such date (the "TDC Agreement"), acquired all of the outstanding shares of TDC Filter Manufacturing, Inc., a Delaware corporation ("TDC"), and the related real estate for cash and options to purchase an aggregate of 75,000 shares of Common Stock. The Company's filtration products business is carried on by Midwesco Filter and TDC, and the piping system products business is carried on by Perma-Pipe, Inc. Midwesco Filter and Perma-Pipe, Inc. are wholly-owned subsidiaries of MFRI. As used herein, unless the context otherwise requires, the term Company“Company” includes MFRI Inc.,and its subsidiaries, Midwesco Filter Thermal Care,Resources, Inc., Perma-Pipe, Inc., TDC,Thermal Care Inc., and their subsidiariesrespective predecessors and predecessors. subsidiaries.

The Company's principalFiltration Products business segment manufactures and sells a wide variety of filter elements for air filtration and particulate collection systems. Air filtration systems are used in many industries in the United States and abroad to limit particulate emissions to comply with environmental regulations. The Filtration Products business segment markets air filtration-related products and accessories, and provides maintenance services, consisting primarily of dust collector inspection, filter cleaning and filter replacement.

The Piping Systems business segment engineers, designs, manufactures and sells specialty piping systems and leak detection and location systems. This segment’s specialty piping systems include (i) industrial and secondary containment piping systems for transporting chemicals, waste streams and petroleum liquids, (ii) insulated and jacketed district heating and cooking piping systems for efficient energy distribution to multiple locations from central energy plants, and (iii) oil and gas gathering flow lines and long lines for oil and mineral transportation. The Piping Systems business segment’s leak detection and location systems are sold as part of many of its piping systems products and on a stand-alone basis, to monitor areas where fluid intrusion may contaminate the environment, endanger personal safety, cause a fire hazard, impair essential services or damage equipment or property.

The Industrial Process Cooling Equipment business segment engineers, designs, manufactures and sells industrial process cooling equipment, including liquid chillers, mold temperature controllers, cooling towers, plan circulating systems, and related accessories for use in industrial process applications.

Our executive offices are located at 7720 Lehigh Avenue, Niles, Illinois, 60714 and itsour telephone number is (847) 966-1000. Other information concerning

USE OF PROCEEDS

Unless we otherwise specify in the Company's management,applicable prospectus supplement, the net proceeds received from the sale of the securities offered by this prospectus and any prospectus supplement will be used for general corporate purposes. General corporate purposes may include the repayment of debt, financing of possible acquisitions, business securities,expansion and resultsworking capital.

PLAN OF DISTRIBUTION

We may sell the shares of operations is incorporatedCommon Stock offered hereby to one or more underwriters for public offering and sale by reference from its reports filed withthem or may sell such shares to investors directly or through agents. Any underwriter or agent involved in the Commission. See "Information Incorporated by Reference." SELLING STOCKHOLDERS The Sharesoffer and sale of such shares will be named in the applicable prospectus supplement.

Underwriters may offer and sell such shares at a fixed price or prices, which may be offeredchanged, at prices related to the prevailing market prices at the time of sale or at negotiated prices. We may, from time to time, forauthorize underwriters acting as our agents to offer and sell such shares upon the account of the Selling Stockholders whose namesterms and conditions as are set forth in the table below. This Prospectus alsoapplicable prospectus supplement. In connection with the sale of such shares, underwriters may be used by transferees, assignees, and pledgees of any of the Selling Stockholders. The table sets forth information as of December 31, 1997 with respectdeemed to the beneficial ownership of the Shares by the Selling Stockholders. To the knowledge of the Company, none of the Selling Stockholders has any material relationship with the Company except as set forthhave received compensation from us in the footnotesform of underwriting discounts or commissions and may also receive commissions from purchasers of such shares for whom they may act as agent. Underwriters may sell such shares to the following table and as more fully described elsewhere in this Prospectus (including the information incorporated by reference in this Prospectus).
NO. OF SHARES OWNED NO. OF SHARES NO. OF SHARES PRIOR TO Offering WHICH MAY BE WHICH MAY BE OWNED SELLING STOCKHOLDER OFFERED AFTER OFFERING Roy E. Greenlees and Lorie 70,500 70,500 0 Greenlees as Joint Tenants {(1)} Janet Marshall{(2)} 4,500 4,500 0
__________________________ {(1) }Roy E. Greenlees is a Director and President of TDC, which is a wholly-owned subsidiary of the Company. {(2) }Janet Marshall is Vice President of TDC. USE OF PROCEEDS This Prospectus relates solely to Shares being offered and sold for the accounts of the Selling Stockholders. The Company will not realize any proceeds from any sale of Shares by the Selling Stockholders. PLAN OF DISTRIBUTION The Selling Stockholders may offer and sell Shares by means of the Prospectus from time to time in one or more transactions, directly by the Selling Stockholders, or through agents, dealers, or brokers to be designated from time to time;and such offers and sales may be effected over any national securities exchange or automated interdealer quotation system on which shares of the Common Stock are then listed, in negotiated transactions or in a combination of such methods of sale; the selling price of the Shares may be at market prices prevailing at the time of sale, at prices related to such prevailing market prices or at negotiated prices; and the Shares may also be offered in coordinated block transactions through underwriters, dealers or agents, or otherwise who may receive compensation in the form of underwriting or brokerage discounts, concessions or commissions from the Selling Stockholders underwriters and/or commissions from the purchasers of such Shares for whom they may act as agents. In certain states, the Selling Stockholders may be requiredagent.

Any underwriting compensation paid by us to offer and sell Shares only through brokers and dealers registered in such states. The Selling Stockholders and any brokersunderwriters or dealers that actagents in connection with the saleoffering of Shares hereunderthe shares of Common Stock offered hereby will be set forth in the applicable prospectus supplement. The prospectus supplement may further state that such underwriters may allow discounts, concessions or commissions to participating dealers. Underwriters, dealers and 


agents participating in the distribution of such shares may be deemed to be "underwriters" within the meaning of Section 2(11) of the Securities Actunderwriters, and any discounts and commissions received by them and any profit realized by them on the saleresale of Shares as principalsuch shares may be deemed to be underwriting discounts and commissions, under the Securities Act. Neither the Company nor the Selling Stockholders can presently estimate the amount of such compensation. The Company knows of no existing arrangements between any selling StockholderUnderwriters, dealers and any underwriter, broker, dealer, or other agent relatingagents may be entitled, under agreements entered into with us, to the sale or distribution of the Shares. The Company will pay all of the expenses of the preparation, printingindemnification against and filing of the Registration Statement, any amendments or supplements thereto, and prospectuses and revised prospectuses as required to cover the transactions covered hereby, as well as the Company's fees and disbursements of its counsel and accountants relating to the Registration Statement, but the Company is not obligated to pay any underwriting discounts and commissions, brokers' commissions or charges, the legal fees and expenses of the Selling Stockholders, or transfer taxes, if any, relating to the sale or disposition of Shares by a Selling Shareholder. Each Selling Stockholder may indemnify any broker, dealer, agent, or underwriter that participates in transactions involving sales of the Shares againstcontribution toward certain civil liabilities, including liabilities arising under the Securities Act.

EXPERTS

The Selling Stockholders may also resell Shares in open market transactions pursuant to the resale provisions of Rule 144 under the Securities Act or in transactions otherwise permitted under the Securities Act. LEGAL MATTERS Certain legal matters in connection with the Shares, including the validityconsolidated financial statements and schedule of the Shares, will be passed uponCompany for the Company by Rudnick & Wolfe, Chicago, Illinois. EXPERTS The Consolidated Financial Statements of MFRI, Inc.years ended January 31, 2006 and subsidiaries incorporated2005 appearing in this Prospectus by reference from the Company'sCompany’s Annual Report on Form 10-K for the year ended January 31, 19972006 have been audited by Grant Thornton LLP, an independent registered public accounting firm, as set forth in their reports thereon included therein, and incorporated herein by reference. Such financial statements have been incorporated herein by reference, in reliance upon such reports given on the Consolidated Financial Statementsauthority of Midwesco, Inc.such firm as experts in accounting and subsidiariesauditing.

The consolidated financial statements and related financial statement schedule for the year ended January 31, 2004, incorporated in this Prospectusprospectus by reference from the Company's CurrentCompany’s Annual Report on Form 8-K dated August 11, 199710-K for the year ended January 31, 2006, have been audited by Deloitte & Touche LLP, an independent auditors,registered public accounting firm, as stated in their reports,report, which areis incorporated herein by reference, and have been so incorporated in reliance upon the reportsreport of such firm given upon their authority as experts in accounting and auditing. INFORMATION INCORPORATED BY REFERENCE

LEGAL MATTERS

The following documents previously filedlegality of the Common Shares offered by the Company or its predecessor withhas been passed upon for us by the Commission pursuant tolaw firm of DLA Piper US LLP, Chicago, Illinois. DLA Piper US LLP attorneys who are participating in the Exchange Act (SEC File No. 0-18370) are hereby incorporated by reference into this Prospectus: (i) the Company's Current Report on Form 8-K dated December 12, 1997; (ii) the Company's Current Report on Form 8-K dated August 11, 1997; (iii) the Company's Annual Report on Form 10-K for the fiscal year ended January 31, 1997; and (iv) the registration statement of Midwesco Filter Resources, Inc., a predecessor and wholly-owned subsidiaryrepresentation of the Company on Form 8-A filed on March 13, 1990 registering common stockin this offering own an aggregate of the Company's predecessor under Section 12(g) of the Securities Exchange Act of 1934. All documents filed by the Company pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this Prospectus and before the termination of the offering of shares of the3,100 Common Stock made hereby are hereby incorporated by reference, and such documents are deemed to be a part hereof from the date of filing of such documents. Any statement contained in a document incorporated or deemed to be incorporated by reference herein shall be modified or superseded for purposes of this Prospectus to the extent that a statement contained herein or in any other subsequently filed document which is or is deemed to be incorporated by reference herein modifies or supersedes such statement. Any such statement so modified or superseded shall not, except as so modified or superseded, constitute a part of this Prospectus. THE COMPANY WILL PROVIDE WITHOUT CHARGE TO EACH PERSON, INCLUDING ANY BENEFICIAL OWNER OF COMMON STOCK, TO WHOM A COPY OF THIS PROSPECTUS IS DELIVERED, UPON THE ORAL OR WRITTEN REQUEST OF SUCH PERSON, A COPY OF ANY AND ALL OF THE INFORMATION THAT HAS BEEN INCORPORATED BY REFERENCE IN THIS PROSPECTUS (NOT INCLUDING EXHIBITS TO THE INFORMATION THAT IS INCORPORATED BY REFERENCE UNLESS SUCH EXHIBITS ARE SPECIFICALLY INCORPORATED BY REFERENCE IN SUCH INFORMATION). SUCH REQUEST SHOULD BE DIRECTED TO MICHAEL D. BENNETT, SECRETARY, Shares.


1,500,000 Shares

MFRI, INC., 7720 LEHIGH AVENUE, NILES, ILLINOIS 60714 (TELEPHONE (847) 966-1000).

Common Stock

PROSPECTUS

_______________, 2006




PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION. Other Expenses Of Issuance And Distribution

The following table sets forth those expenses for distribution to be incurred in connection with the issuance and distribution of the securities being registered hereby: S.E.C. registration fee $ 180.00 *Legal and accounting fees and expenses $ 10,000.00 *Miscellaneous $ 1,820.00 Total $ 12,000.00 The Company has agreed to pay all of the expenses of the preparation, printing and filing of the Registration Statement, any amendments or supplements thereto, and prospectuses and revised prospectuses as required to cover the transactions covered hereby, as well as the Company's fees and disbursements of its counsel and accountants relating to the Registration Statement, but the Selling Stockholders will bear their pro rata portion of any underwriting discounts and commissions, brokers' commissions or charges, or other costs arising in the marketing of the Shares and their own legal fees and expenses. ________________ * Estimated. registered.

Registration Fee

$3,535

Legal Fees and Expenses*

7,500

Accounting Fees and Expenses*

20,000

Printing and Duplicating Expenses*

1,000

Miscellaneous*

1,000

Total*

$33,035

__________

* Estimated

 II-1



Item 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS. Indemnification Of Directors And Officers

Section 145 of the Delaware General Corporation Law authorizes indemnification of directors, officers, employees and agents of the Company; allows the advancement of costs of defending against litigation; and permits companies incorporated in Delaware to purchase insurance on behalf of directors, officers, employees and agents against liabilities whether or not in the circumstances such companies would have the power to indemnify against such liabilities under the provisions of the statute.

The Company'sCompany’s Certificate of Incorporation and its By-Laws provide for indemnification of its officers and directors to the full extent permitted by Section 145 of the Delaware General Corporation Law.

The Company'sCompany’s Certificate of Incorporation eliminates, to the fullest extent permitted by Delaware law, liability of a director to the Company or its stockholders for monetary damages for a breach of such director'sdirector’s fiduciary duty of care except for liability where a director (a) breaches his or her duty of loyalty to the Company or its stockholders, (b) fails to act in good faith or engages in intentional misconduct or knowing violation of law, (c) authorizes payment of an illegal dividend or a stock repurchase or (d) obtains an improper personal benefit. While liability for monetary damages has been eliminated, equitable remedies such as injunctive relief or rescission remain available. In addition, a director is not relieved of his responsibilities under any other law, including the federal securities laws.

The Company has entered into indemnification agreements in the form described below with each person who is currently a member of the Board of Directors of the Company and will enter into such agreements with persons who in the future become directors of the Company. Such indemnification agreements provide for indemnification against any and all expenses incurred in connection with, as well as any and all judgments, fines, and amounts paid in settlement resulting from, any threatened, pending, or completed action, suit, or proceeding, whether civil, criminal, administrative, or investigative (collectively an "Action"“Action”), by reason of the fact that such director is or was a director, officer, employee or agent of the Company, or is or was serving at the request of the Company as a director, officer, employee or agent of another corporation, partnership, joint venture, trust, or other enterprise. The indemnification agreements provide that if any payment, advance or indemnification of the director requires that he or she acted in good faith, in a manner he or she reasonably believed to be for or not opposed to the best interests of the Company or without reasonable cause to believe his or her conduct was unlawful, then it shall be presumed that he or she so acted unless proven otherwise by clear and convincing evidence. The indemnification agreements also provide for the advancement of all expenses, including reasonable attorneys'attorneys’ fees, arising from the investigation of any claim, preparation for the defense or defense or settlement of an Action. The indemnification agreements authorize the Company to participate in the defense of any action and to assume the defense thereof, with counsel who shall be reasonably satisfactory to the director, provided that the director shall be entitled to separate counsel of his or her choosing if he or she reasonably believes that (i) there exists conflictingconflicts interests between himself or herself and the Company or other parties (the defense of whom the Company shall have assumed) or (ii) there is any substantial likelihood that the Company will be financially or legally unable to satisfy its obligations under the Indemnification Agreement. The indemnification agreements provide that a director'sdirector’s rights under such contract are not exclusive of any other indemnification rights he or she may have under any provision of law, the Company'sCompany’s Certificate of Incorporation or By-laws, the vote of the Company'sCompany’s stockholders or disinterested directors, other agreements or otherwise. Item

ITEM 16. EXHIBITS. EXHIBIT EXHIBIT NUMBER DESCRIPTION 2.1 Stock Purchase Agreement dated December 3, 1997 by and between Roy E. Greenlees, Lorie Greenlees, Janet Marshall and MFRI, Inc. incorporated by reference in Current Report on Form 8-K dated December 12, 1997 (SEC File No. 0-18370). 5 Form of Opinion of Rudnick & Wolfe with respect to the legality of the Common Stock being registered 23.1 Consent of Deloitte & Touche LLP 23.2 Consent of Rudnick & Wolfe (contained in Exhibit 5 hereof) 24 Power of Attorney of directors and certain officers of the Company. ItemExhibits

4.1*

-

Certificate of Incorporation of MFRI, Inc.

4.2**

-

By-laws of MFRI, Inc.

5

-

Opinion of DLA Piper US LLP

23.1

-

Consent of Grant Thornton LLP

23.2

Consent of Deloitte & Touche LLP

23.3

-

Consent of DLA Piper US LLP (included in Exhibit 5)

24

-

Power of Attorney

____________________

*

Incorporated by reference to Exhibit 3.3 to Registration Statement No. 33-70298.

**

Incorporated by reference to Exhibit 3.4 to Registration Statement No. 33-70298.

ITEM 17. UNDERTAKINGS. The Registrant hereby undertakes: (1) To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement; (i) To include any prospectus required by Section 10(a)(3) of the Securities Act of 1933; (ii) To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in the registration statement; (iii) To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in the registration statement; PROVIDED, HOWEVER,Undertakings

(a)

The undersigned Registrant hereby undertakes:

(1)

To file, during any period in which offers or sales are being made, a post-effective amendment to this registration statement:

II-2 



(i)

To include any prospectus required by section 10(a)(3) of the Securities Act of 1933;

(ii)

To reflect in the prospectus any facts or events arising after the effective date of the registration statement (or the most recent post-effective amendment thereof) which, individually or in the aggregate, represent a fundamental change in the information set forth in this registration statement. Notwithstanding the foregoing, any increase or decrease in volume of securities offered (if the total dollar value of securities offered would not exceed that which was registered) and any deviation from the low or high end of the estimated maximum offering range may be reflected in the form of prospectus filed with the Commission pursuant to Rule 424(b) if, in the aggregate, the changes in volume and price represent no more than a 20 percent change in the maximum aggregate offering price set forth in the “Calculation of Registration Fee” table in the effective registration statement;

(iii)

To include any material information with respect to the plan of distribution not previously disclosed in the registration statement or any material change to such information in this registration statement;

provided, however, that paragraphs (a)(1)subparagraphs (i) and (a)(1)(ii) above do not apply if the registration statement is on Form S-3, Form S-8 or Form F-3, and the information required to be included in a post-effective amendment by those paragraphs is contained in the periodic reports filed with or furnished to the Commission by the Registrant pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934 that are incorporated by reference in thethis registration statement.

(2)           That, for the purpose of determining any liability under the Securities Act of 1933, each such post-effective amendment shall be deemed to be a new registration statement relating to the securities offered therein,herein, and the offering of such securities at that time shall be deemed to be the initial BONA FIDEbonafide offering thereof.

(3)           To remove from registration by means of a post- effectivepost-effective amendment any of the securities being registered which remain unsold at the termination of the offering.

(4)           That, for the purpose of determining liability under the Securities Act of 1933 to any purchaser:

(A)          Each prospectus filed by a registrant pursuant to Rule 424(b)(3) shall be deemed to be part of the registration statement as of the date the filed prospectus was deemed part of and included in the registration statement; and

(B)          Each prospectus required to be filed pursuant to Rule 424(b)(2), (b)(5) or (b)(7) as part of a registration statement in reliance on Rule 430B relating to an offering made pursuant to Rule 415(a)(1)(i), (vii) or (x) for the purpose of providing the information required by Section 10(a) of the Securities Acct of 1933 shall be deemed to be part of and included in the registration statement as of the earlier of the date such form of prospectus is first used after effectiveness or the date of the first contract of sale of securities in the offering described in the prospectus. As provided in Rule 430B, for liability purposes of the issuer and any person that is at that date an underwriter, such date shall be deemed to be a new effective date of the registration statement relating to the securities in the registration statement to which the prospectus relates, and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof. Provided, however, that no statement made in a registration statement or prospectus that is part of the registration statement or made in a document incorporated or deemed incorporated by reference into the registration statement or prospectus that is part of the registration statement will, as to a purchaser with a time of contract of sale prior to such effective date, supersede or modify any statement that was made in the registration statement or prospectus that was part of the registration statement or made in any such document immediately prior to such effective date.

(5)           That, for the purpose of determining liability of a registrant under the Securities Act of 1933 to any purchaser in the initial distribution of the securities, the registrant undertakes that in a primary offering of securities of the registrant pursuant to this registration statement, regardless of the underwriting method used to sell the securities to the purchaser, if the securities are offered or sold to such purchaser by means of any of the following communications, the registrant will be a seller to the purchaser and will be considered to offer or sell such securities to such purchaser:

(i)

Any preliminary prospectus or prospectus of the registrant relating to the offering required to be filed pursuant to Rule 424;

(ii)

Any free writing prospectus relating to the offering prepared by or on behalf of the registrant or used or referred to by the registrant;

II-3 



(iii)

The portion of any other free writing prospectus relating to the offering containing material information about the registrant or its securities provided by or on behalf of the registrant; and

(iv)

Any other communication that is an offer in the offering made by the registrant to the purchaser.

(b)           The undersigned registrantRegistrant hereby further undertakes that, for the purposes of determining any liability under the Securities Act of 1933, each filing of the registrant'sRegistrant’s annual report pursuant to Section 13(a) or Section 15(d) of the Securities Exchange Act of 1934 (and, where applicable, each filing of an employee benefit plan's annual report pursuant to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated by reference in thethis registration statement shall be deemed to be a new registration statement relating to the securities offered therein,herein, and the offering of such securities at that time shall be deemed to be the initial BONA FIDEbona fide offering thereof. The undersigned registrant hereby undertakes to deliver or cause to be delivered with the Prospectus, to each person to whom the Prospectus is sent or given, the latest annual report to security holders that is incorporated by reference in the Prospectus and furnished pursuant to and meeting the requirements of Rule 14a-3 or Rule 14c-3 under the Securities Exchange Act of 1934; and, where interim financial information required to be presented by Article 3 of Regulation S-X is not set forth in the Prospectus, to deliver, or cause to be delivered to each person to whom the Prospectus is sent or given, the latest quarterly report that is specifically incorporated by reference in the Prospectus to provide such interim financial information.

(c)           Insofar as indemnification for liabilities arising under the Securities Act of 1933 may be permitted to directors, officers and controlling persons of the registrantRegistrant pursuant to the foregoing provisions or otherwise, the registrant has been advised that in the opinion of the Securities and Exchange Commission such indemnification is against public policy as expressed in the Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director,trustee, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director,trustee, officer or controlling person in connection with the securities being registered, the registrantRegistrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Act and will be governed by the final adjudication of such issue.

II-4 



SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrantRegistrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-3 and has duly caused this registration statementRegistration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Niles, State of Illinois, on January 22, 1998. MFRI, INC. By:/S/ DAVID UNGER David Unger Chief Executive Officer By:/S/ DAVID UNGER David Unger Chairman of the Board By:/S/ DAVID UNGER David Unger President

MFRI, INC.

By:

/s/ David Unger

David Unger, Chairman of the Board and Chief Executive Officer

Pursuant to the requirements of the Securities Act of 1933, this registration statementRegistration Statement has been signed below by the following persons in the capacities set forth below and on the date indicated. SIGNATURE TITLE DATE /s/ David Unger* Director and Chairman of the Board of Directors (Principal Executive Officer) January 22, 1998 Henry M. Mautner* Director, Vice Chairman of the Board of Directors January 22, 1998 Michael D. Bennett* Vice President, Secretary and Treasurer (Principal Financial and Accounting Officer) January 22, 1998 Arnold F. Brookstone* Director January 22, 1998 Don Gruenberg* Director January 22, 1998 Bradley E. Mautner* Director January 22, 1998 Eugene Miller* Director January 22, 1998 Gene K. Ogilvie* Director January 22, 1998 Stephen B. Schwartz* Director January 22, 1998 *By:/S/ DAVID UNGER Individually and as Attorney- January 22, 1998 David Unger in-fact

dates indicated:

Signature

Title

Date**

David Unger*

Director, Chief Executive Officer and Chairman of the Board of Directors (Principal Executive Officer)

Bradley E. Mautner*

Director, President and Chief Operating Officer

Henry M. Mautner*

Director and Vice Chairman of the Board of Directors

Michael D. Bennett*

Vice President, Secretary and Treasurer (Principal Financial and Accounting Officer)

Arnold F. Brookstone*

Dennis Kessler*

Eugene Miller*

Stephen B. Schwartz*

Director

Director

Director

Director

*By

/s/ David Unger


Individually and as Attorney-in-fact

David Unger

**December 15, 2006

II-5 



EXHIBIT INDEX

Exhibit

Number

Exhibit

Description

4.1*

Certificate of Incorporation of MFRI, Inc.

4.2**

By-laws of MFRI, Inc.

5

Opinion of DLA Piper US LLP

23.1

Consent of Grant Thornton LLP

23.2

Consent of Deloitte & Touche LLP

23.3

Consent of DLA Piper US LLP (included in Exhibit 5)

24

Power of Attorney

____________________

*

Incorporated by reference to Exhibit 3.3 to Registration Statement No. 33-70298.

**

Incorporated by reference to Exhibit 3.4 to Registration Statement No. 33-70298.