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                                  EXHIBIT 4.6

                          THIRD SUPPLEMENTAL INDENTURE

         THIRD SUPPLEMENTAL INDENTURE (this "Supplemental Indenture"), dated as
of November 1, 2002, is by and among ICO P&O, Inc., a Delaware corporation (the
"Company"), as successor by merger to ICO P&O, Inc., a Texas corporation
formerly known as ICO, Inc. ("Old ICO"), ICO, Inc., a Texas corporation formerly
known as ICO Holdings, Inc. that wholly owns the Company ("New ICO"), as
additional obligor, and State Street Bank and Trust Company, a Massachusetts
trust company and successor-in-interest to Fleet National Bank, as trustee (the
"Trustee").

RECITALS

         WHEREAS, Old ICO (then known as ICO, Inc.), as issuer, and the Trustee
entered into that certain indenture, dated as of June 9, 1997, and such
Indenture was supplemented and amended by (i) the First Supplemental Indenture,
dated as of April 1, 1998, by and among Old ICO, New ICO (then known as ICO
Holdings, Inc.) and the Trustee and (ii) the Second Supplemental Indenture,
dated as of April 1, 1998, by and among the Company, New ICO and the Trustee
(such Indenture, as so supplemented and amended, being hereinafter called the
"Indenture");

         WHEREAS, on June 9, 1997, Old ICO issued $120,000,000 aggregate
principal amount of its 10 3/8% Series A Senior Notes due 2007, and it
subsequently exchanged them for an equal aggregate principal amount of its
10 3/8% Series B Senior Notes due 2007 pursuant to the Exchange Offer;

         WHEREAS, New ICO beneficially owns Notes in the aggregate principal
amount of $5,425,000, so there are now outstanding under the Indenture Notes in
the aggregate principal amount of $114,575,000;

         WHEREAS, Section 9.2 of the Indenture provides that, with the consent
of the Holders of a majority in principal amount of the Notes then outstanding
(including consents obtained in connection with a tender offer for the Notes),
the Company, when authorized by a resolution of its Board of Directors
Resolution, and the Trustee may enter into an indenture supplemental to the
Indenture for the purpose of amending or supplementing any provisions of the
Indenture (with certain exceptions not relevant to this Supplemental Indenture);

         WHEREAS, Section 9.2 of the Indenture further provides that (subject to
certain exceptions not relevant to this Supplemental Indenture) the Holders of a
majority in principal amount of the Notes then outstanding may waive compliance
in a particular instance by the Company with any provision of the Indenture;

         WHEREAS, the Company and New ICO desire and have requested the Trustee
to join with them in entering into this Supplemental Indenture for the purpose
of amending the Indenture in certain respects as permitted by Section 9.2 of the
Indenture and evidencing the waiver of the Company's compliance with certain
provisions of Section 4.13 of the Indenture;

         WHEREAS, the Company has been soliciting consents to this Supplemental
Indenture upon the terms and subject to the conditions set forth in its Amended
Offer to Purchase and


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Consent Solicitation Statement dated October 16, 2002 and the related Consent
and Letter of Transmittal (which together, including any amendments,
modifications or supplements thereto, constitute the "Tender Offer");

         WHEREAS, the Company (1) has received the consent of the Holders of,
and will accept for payment under the Tender Offer promptly after the effective
date referred to in Section 4.3 hereof, more than a majority in principal amount
of the outstanding Notes, all as certified by an Officers' Certificate delivered
to the Trustee simultaneously with the execution and delivery of this
Supplemental Indenture, (2) has delivered to the Trustee simultaneously with the
execution and delivery of this Supplemental Indenture an Opinion of Counsel
relating to this Supplemental Indenture as contemplated by Section 9.6 of the
Indenture and (3) has satisfied all other conditions required under Article 9 of
the Indenture to enable the Company, New ICO and the Trustee to enter into this
Supplemental Indenture.

         NOW, THEREFORE, in consideration of the foregoing and for other good
and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the Company, New ICO and the Trustee mutually covenant and agree
for the equal and ratable benefit of the Holders as follows:

                                    ARTICLE I
                                   DEFINITIONS

         1.1 DELETION OF DEFINITIONS AND RELATED REFERENCES. Section 1.1 of
Article 1 of the Indenture is hereby amended to delete in their entirety all
terms and their respective definitions for which all references are eliminated
in the Indenture as a result of the amendments set forth in Article II of this
Supplemental Indenture.

                                   ARTICLE II
                             AMENDMENTS TO INDENTURE

         2.1 AMENDMENTS TO ARTICLES 1, 4, 5 AND 6. The Indenture is hereby
amended by (A) substituting $150.0 million for $2.0 million in each of
subclauses (a) and (b) of the initial clause (iii) of the definition of "Asset
Sale" in Section 1.1 and (B) by deleting the following sections of the Indenture
and all references thereto in their entirety: subsection (a) of Section 4.3
(Reports); Section 4.5 (Taxes); Section 4.7 (Company and Corporate Existence and
Maintenance of Properties and Insurance); Section 4.8 (Limitation on Incurrence
of Indebtedness and Issuance of Disqualified Stock); Section 4.9 (Limitation on
Restricted Payments): Section 4.10 (Limitation on Liens); Section 4.11
(Limitation on Transactions with Affiliates); Section 4.12 (Limitation on
Dividend and Other Payment Restrictions); Section 4.15 (Limitation on
Sale/Leaseback Transactions); Section 4.16 (Guarantees of Certain Indebtedness);
Section 4.17 (Conduct of Business); Section 4.18 (Payments for Consent); each of
clauses (iii), (iv) and (v) of subsection (a) of Section 5.1 (Limitation on
Merger, Consolidation or Sale of Assets); and each of subsections (5), (6) and
(7) of Section 6.1 (Events of Default).

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                                   ARTICLE III
                                     WAIVER

         3.1 WAIVER OF COMPLIANCE WITH SECTION 4.13. Neither the Company nor New
ICO shall have any obligation, pursuant to Section 4.13 of the Indenture, to
offer to repurchase any Notes with any of the Net Cash Proceeds of the Asset
Sale effected on September 6, 2002 involving the sale of the Oilfield Services
division of the Company described in the Tender Offer.

                                   ARTICLE IV
                                  MISCELLANEOUS

         4.1 DEFINITIONS. Capitalized terms used herein without definition shall
have the meanings assigned to them in the Indenture. For all purposes of this
Supplemental Indenture, except as otherwise herein expressly provided or unless
the context otherwise requires, the words "herein," "hereof" and "hereby" and
other words of similar import used in this Supplemental Indenture refer to this
Supplemental Indenture as a whole and not to any particular section hereof.

         4.2 RATIFICATION OF INDENTURE; SUPPLEMENTAL INDENTURE PART OF
INDENTURE. Except as expressly amended hereby, the Indenture is in all respects
ratified and confirmed and all the terms, conditions and provisions thereof
shall remain in full force and effect. This Supplemental Indenture shall form a
part of the Indenture for all purposes, and every Holder of Notes heretofore or
hereafter authenticated and delivered under the Indenture shall be bound hereby
and all terms and conditions of both shall be read together as though they
constitute a single instrument, except that in the case of conflict the
provisions of this Supplemental Indenture shall control.

         4.3 EFFECTIVE DATE. The provisions of this Supplemental Indenture shall
be effective only upon execution and delivery of this instrument by the parties
hereto immediately prior to the closing of the Tender Offer and the purchase of
the Notes by New ICO. Notwithstanding the foregoing sentence, the provisions of
this Supplemental Indenture shall become operative only upon the purchase of
more than a majority in principal amount of the outstanding Notes pursuant to
the Tender Offer. New ICO shall notify the Trustee in writing promptly after the
occurrence of such purchase.

         4.4 ENDORSEMENT AND CHANGE OF FORM OF NOTES. Any Notes authenticated
and delivered after the close of business on the date that this Supplemental
Indenture becomes operative in substitution for Notes then outstanding and all
Notes presented or delivered to the Trustee on and after that date for such
purpose shall be stamped, imprinted or otherwise legended by the Trustee, with a
notation as follows:

                  "Effective as of November 1, 2002, certain restrictive
         covenants of the Company and certain Events of Default have been
         eliminated or limited, as provided in the Third Supplemental Indenture,
         dated as of November 1, 2002. Reference is hereby made to said Third
         Supplemental Indenture, copies of which are on file with the Trustee,
         for a description of the amendments made therein."

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         4.5 GOVERNING LAW. This Supplemental Indenture shall be governed by and
construed in accordance with the laws of the State of New York.

         4.6 TRUSTEE MAKES NO REPRESENTATION. The Trustee makes no
representation as to the validity or sufficiency of this Supplemental Indenture.

         4.7 COUNTERPARTS. The parties may sign any number of copies or
counterparts of this Supplemental Indenture. Each signed copy shall be an
original, but all of them together represent the same agreement.

         4.8 EFFECT OF HEADINGS. The Section headings herein are for convenience
only and shall not affect the construction thereof.

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         IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed as of the date first above written.

                                    COMPANY:

                                    ICO P&O, INC.

                                    By:    /s/ Brad Leuschner

                                    Name:  Brad Leuschner

                                    Title:  President


                                    ADDITIONAL OBLIGOR:

                                    ICO, INC.

                                    By:    /s/ Jon C. Biro

                                    Name: Jon C. Biro

                                    Title: Chief Financial Officer and President


                                    TRUSTEE:

                                    STATE STREET BANK AND TRUST COMPANY,
                                      as Trustee

                                    By:    /s/ Dawn P. Heintz

                                    Name: Dawn P. Heintz

                                    Title: Officer