<PAGE>

    As filed with the Securities and Exchange Commission on June 20, 2001.
                                                           Registration No. 333-
================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                          ___________________________


                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                          ___________________________


                        GUNDLE/SLT ENVIRONMENTAL, INC.
            (Exact Name of Registrant as Specified in Its Charter)
                          ___________________________


                                   Delaware
        (State or Other Jurisdiction of Incorporation or Organization)

                                  22-2731074
                     (I.R.S. Employer Identification No.)

                               19103 Gundle Road
                             Houston, Texas 77073
  (Address, including Zip Code, of Registrant's Principal Executive Offices)

                        GUNDLE/SLT ENVIRONMENTAL, INC.
                           1995 INCENTIVE STOCK PLAN
                      AS AMENDED AND RESTATED MAY 3, 2001
                           (Full Title of the Plans)

                          ___________________________

     Name, Address and Telephone                 Copy of communications to:
    Number of Agent for Service:

            C. Wayne Case                             T. William Porter
    Secretary and General Counsel                  Porter & Hedges, L.L.P.
    Gundle/SLT Environmental, Inc.                700 Louisiana, 35th Floor
          19103 Gundle Road                       Houston, Texas 77002-2764
         Houston, Texas 77073                      Phone:  (713) 226-0600
        Phone: (281) 443-8564                       Fax:  (713) 228-1331
         Fax: (281) 875-6010


                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
====================================================================================================================================
                                                                   Proposed Maximum           Proposed
       Title of Securities to be Registered        Amount to           Offering          Maximum Aggregate          Amount of
                                                be Registered(1)   Price per Share(2)     Offering Price(2)      Registration Fee
------------------------------------------------------------------------------------------------------------------------------------
<S>                                             <C>                <C>                   <C>                     <C>
Common Stock, par value $.01 per share             650,000              $2.50               $1,625,000                $408
====================================================================================================================================
</TABLE>

  (1)  Pursuant to Rule 416(a), also registered hereunder is an indeterminate
       number of shares of Common Stock issuable as a result of the anti-
       dilution provision of the Gundle/SLT Environmental, Inc. 1995 Incentive
       Stock Plan As Amended and Restated May 3, 2001 (the "Plan").

  (2)  Pursuant to Rule 457(c), the registration fee is calculated on the basis
       of the average of the high and low price of the Common Stock on the New
       York Stock Exchange Composite Tape on June 19, 2001, $2.50 per share.
       Pursuant to General Instruction E to Form S-8, the registration fee is
       calculated only with respect to the additional securities registered
       under the Plan.
<PAGE>

     This registration statement registers an additional 650,000 shares of
Common Stock related to the Plan which are the same class as other securities
for which a registration statement on Form S-8, No.333-001759 (the "Previous
Registration Statement"), has been previously filed. The Previous Registration
Statement registered 1,750,000 shares of Common Stock related to the Plan.
Pursuant to General Instruction E of Form S-8, the contents of the Previous
Registration Statement are hereby incorporated by reference.


                                    PART II

              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 5.   INTEREST OF NAMED EXPERTS AND COUNSEL

     T. William Porter is the Chairman of Porter & Hedges, L.L.P., the
Registrant's principal outside counsel, and is also a director of the
Registrant.

ITEM 8.   EXHIBITS


   Exhibits                            Description
   --------                            -----------

      4.1   -  1995 Incentive Stock Plan As Amended and Restated May 3, 2001
               (filed herewith).
      5.1   -  Opinion of Porter & Hedges, L.L.P. with respect to legality of
               securities (filed herewith).
     23.1   -  Consent of Ernst & Young LLP (filed herewith).
     23.2   -  Consent of Porter & Hedges, L.L.P. (included in Exhibit 5.1).
     24.1   -  Powers of Attorney (included on signature page).

                                       2
<PAGE>

                                  SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Houston, State of Texas, on June 20, 2001.

                                   GUNDLE/SLT ENVIRONMENTAL, INC.



                                   By: /s/ Samir T. Badawi
                                      ------------------------------------------
                                       Samir T. Badawi, Chairman of the Board
                                       President and Chief Executive Officer

                               POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Samir T. Badawi, Roger J. Klatt and C. Wayne Case
and each of them, either of whom may act without joinder of the other, his true
and lawful attorneys-in-fact and agents, with full power of substitution and
resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all pre- and post-effective amendments and
supplements to this Registration Statement, and to file the same, or cause to be
filed the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto such
attorneys-in-fact and agents, and each of them, full power and authority to do
and perform each and every act and thing requisite and necessary to be done in
and about the premises, as fully to all intents and purposes as he might or
could do in person, hereby ratifying and confirming all that said attorneys-in-
fact and agents, and each of them, or the substitute or substitutes of either of
them, may lawfully do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.

<TABLE>
<CAPTION>
            Signature                                          Title                            Date
            ---------                                          -----                            ----
<S>                                              <C>                                        <C>
      /s/ Samir T. Badawi                        Chairman of the Board, President and       June 20, 2001
--------------------------------------                  Chief Executive Officer
          Samir T. Badawi                            (Principal Executive Officer)

      /s/ Roger J. Klatt                            Executive Vice President, Chief         June 20, 2001
--------------------------------------              Financial Officer and Treasurer
          Roger J. Klatt                               (Principal Financial and
                                                          Accounting Officer)

      /s/ James R. Burke                                       Director                     June 20, 2001
--------------------------------------
          James R. Burke

      /s/ Bruce Cummings                                       Director                     June 20, 2001
--------------------------------------
          Bruce Cummings

      /s/ James R. Gibbs                                       Director                     June 20, 2001
--------------------------------------
          James R. Gibbs

      /s/ T. William Porter                                    Director                     June 20, 2001
--------------------------------------
          T. William Porter

     /s/ Edward T. Sheehan                                     Director                     June 20, 2001
--------------------------------------
         Edward T. Sheehan
</TABLE>

                                       3
<PAGE>


                               INDEX TO EXHIBITS




   Exhibits                           Description
   --------                           -----------

      4.1   -  1995 Incentive Stock Plan As Amended and Restated May 3, 2001
               (filed herewith).

      5.1   -  Opinion of Porter & Hedges, L.L.P. with respect to legality of
               securities (filed herewith).

     23.1   -  Consent of Ernst & Young LLP (filed herewith).

     23.2   -  Consent of Porter & Hedges, L.L.P. (included in Exhibit 5.1).

     24.1   -  Powers of Attorney (included on signature page).

                                       4
[{"type": "S-8", "sequence": "1", "filename": "ds8.txt", "description": "FORM S-8", "secsgml_size_bytes": 9990}]
{"company-data": {"conformed-name": "GUNDLE SLT ENVIRONMENTAL INC", "cik": "0000805023", "assigned-sic": "3081", "irs-number": "222731074", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-63466", "film-number": "1664292"}, "business-address": {"street1": "19103 GUNDLE RD", "city": "HOUSTON", "state": "TX", "zip": "77073", "phone": "7134438564"}, "mail-address": {"street1": "19103 GUNDLE ROAD", "city": "HOUSTON", "state": "TX", "zip": "77073"}, "former-company": [{"former-conformed-name": "GSE LINING TECHNOLOGY INC", "date-changed": "19960513"}, {"former-conformed-name": "GUNDLE ENVIRONMENTAL SYSTEMS INC", "date-changed": "19920703"}]}
As filed with the Securities and Exchange Commission on June 20, 2001.
                                                           Registration No. 333-
================================================================================

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                          ___________________________

                                   FORM S-8
                            REGISTRATION STATEMENT
                                     UNDER
                          THE SECURITIES ACT OF 1933

                          ___________________________

                        GUNDLE/SLT ENVIRONMENTAL, INC.
            (Exact Name of Registrant as Specified in Its Charter)
                          ___________________________

                                   Delaware
        (State or Other Jurisdiction of Incorporation or Organization)

                                  22-2731074
                     (I.R.S. Employer Identification No.)

                               19103 Gundle Road
                             Houston, Texas 77073
  (Address, including Zip Code, of Registrant's Principal Executive Offices)

                        GUNDLE/SLT ENVIRONMENTAL, INC.
                           1995 INCENTIVE STOCK PLAN
                      AS AMENDED AND RESTATED MAY 3, 2001
                           (Full Title of the Plans)

                          ___________________________

     Name, Address and Telephone                 Copy of communications to:
    Number of Agent for Service:

            C. Wayne Case                             T. William Porter
    Secretary and General Counsel                  Porter & Hedges, L.L.P.
    Gundle/SLT Environmental, Inc.                700 Louisiana, 35th Floor
          19103 Gundle Road                       Houston, Texas 77002-2764
         Houston, Texas 77073                      Phone:  (713) 226-0600
        Phone: (281) 443-8564                       Fax:  (713) 228-1331
         Fax: (281) 875-6010

                        CALCULATION OF REGISTRATION FEE
====================================================================================================================================
                                                                   Proposed Maximum           Proposed
       Title of Securities to be Registered        Amount to           Offering          Maximum Aggregate          Amount of
                                                be Registered(1)   Price per Share(2)     Offering Price(2)      Registration Fee
------------------------------------------------------------------------------------------------------------------------------------
Common Stock, par value $.01 per share             650,000              $2.50               $1,625,000                $408
====================================================================================================================================
(1)  Pursuant to Rule 416(a), also registered hereunder is an indeterminate
       number of shares of Common Stock issuable as a result of the anti-
       dilution provision of the Gundle/SLT Environmental, Inc. 1995 Incentive
       Stock Plan As Amended and Restated May 3, 2001 (the "Plan").

  (2)  Pursuant to Rule 457(c), the registration fee is calculated on the basis
       of the average of the high and low price of the Common Stock on the New
       York Stock Exchange Composite Tape on June 19, 2001, $2.50 per share.
       Pursuant to General Instruction E to Form S-8, the registration fee is
       calculated only with respect to the additional securities registered
       under the Plan.
This registration statement registers an additional 650,000 shares of
Common Stock related to the Plan which are the same class as other securities
for which a registration statement on Form S-8, No.333-001759 (the "Previous
Registration Statement"), has been previously filed. The Previous Registration
Statement registered 1,750,000 shares of Common Stock related to the Plan.
Pursuant to General Instruction E of Form S-8, the contents of the Previous
Registration Statement are hereby incorporated by reference.

                                    PART II

              INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 5.   INTEREST OF NAMED EXPERTS AND COUNSEL

     T. William Porter is the Chairman of Porter & Hedges, L.L.P., the
Registrant's principal outside counsel, and is also a director of the
Registrant.

ITEM 8.   EXHIBITS

   Exhibits                            Description
   --------                            -----------

      4.1   -  1995 Incentive Stock Plan As Amended and Restated May 3, 2001
               (filed herewith).
      5.1   -  Opinion of Porter & Hedges, L.L.P. with respect to legality of
               securities (filed herewith).
     23.1   -  Consent of Ernst & Young LLP (filed herewith).
     23.2   -  Consent of Porter & Hedges, L.L.P. (included in Exhibit 5.1).
     24.1   -  Powers of Attorney (included on signature page).

                                       2
SIGNATURES

     Pursuant to the requirements of the Securities Act of 1933, the Registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Houston, State of Texas, on June 20, 2001.

                                   GUNDLE/SLT ENVIRONMENTAL, INC.

                                   By: /s/ Samir T. Badawi
                                      ------------------------------------------
                                       Samir T. Badawi, Chairman of the Board
                                       President and Chief Executive Officer

                               POWER OF ATTORNEY

     KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Samir T. Badawi, Roger J. Klatt and C. Wayne Case
and each of them, either of whom may act without joinder of the other, his true
and lawful attorneys-in-fact and agents, with full power of substitution and
resubstitution, for him and in his name, place and stead, in any and all
capacities, to sign any or all pre- and post-effective amendments and
supplements to this Registration Statement, and to file the same, or cause to be
filed the same, with all exhibits thereto, and other documents in connection
therewith, with the Securities and Exchange Commission, granting unto such
attorneys-in-fact and agents, and each of them, full power and authority to do
and perform each and every act and thing requisite and necessary to be done in
and about the premises, as fully to all intents and purposes as he might or
could do in person, hereby ratifying and confirming all that said attorneys-in-
fact and agents, and each of them, or the substitute or substitutes of either of
them, may lawfully do or cause to be done by virtue hereof.

     Pursuant to the requirements of the Securities Act, this registration
statement has been signed by the following persons in the capacities and on the
dates indicated.
Signature                                          Title                            Date
            ---------                                          -----                            ----
/s/ Samir T. Badawi                        Chairman of the Board, President and       June 20, 2001
--------------------------------------                  Chief Executive Officer
          Samir T. Badawi                            (Principal Executive Officer)

      /s/ Roger J. Klatt                            Executive Vice President, Chief         June 20, 2001
--------------------------------------              Financial Officer and Treasurer
          Roger J. Klatt                               (Principal Financial and
                                                          Accounting Officer)

      /s/ James R. Burke                                       Director                     June 20, 2001
--------------------------------------
          James R. Burke

      /s/ Bruce Cummings                                       Director                     June 20, 2001
--------------------------------------
          Bruce Cummings

      /s/ James R. Gibbs                                       Director                     June 20, 2001
--------------------------------------
          James R. Gibbs

      /s/ T. William Porter                                    Director                     June 20, 2001
--------------------------------------
          T. William Porter

     /s/ Edward T. Sheehan                                     Director                     June 20, 2001
--------------------------------------
         Edward T. Sheehan
3
INDEX TO EXHIBITS

   Exhibits                           Description
   --------                           -----------

      4.1   -  1995 Incentive Stock Plan As Amended and Restated May 3, 2001
               (filed herewith).

      5.1   -  Opinion of Porter & Hedges, L.L.P. with respect to legality of
               securities (filed herewith).

     23.1   -  Consent of Ernst & Young LLP (filed herewith).

     23.2   -  Consent of Porter & Hedges, L.L.P. (included in Exhibit 5.1).

     24.1   -  Powers of Attorney (included on signature page).

                                       4