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Exhibit 10.58

Certain portions of this Exhibit have been filed separately with the
Commission and are subject to a request for confidential treatment.

                          STOCK PURCHASE AGREEMENT

         AGREEMENT FOR THE PURCHASE AND SALE OF STOCK dated as of September
17, 1998, by and between AMBI INC., a New York corporation ("AMBI"), and
AMERICAN HOME PRODUCTS CORPORATION, a Delaware corporation ("AHP").

                            PRELIMINARY STATEMENT

         The parties are concurrently herewith entering into a License, Option 
and Marketing Agreement dated the date hereof (the "Product Agreement"). The 
terms "Effective Date," "HSR Act," "Product," "Option Product," and "Additional
Product" shall have the meanings attributed thereto in the Product Agreement.

         The parties wish to provide for certain purchases by AHP of common
stock of AMBI ("common stock") and for certain agreements in connection
therewith.

         NOW, THEREFORE, in consideration of the premises and the
representations, warranties, covenants and agreements herein contained, the
parties hereto agree as follows:

1.   Purchases and Sales of AMBI Stock

     1.1. Base Purchase.

         1.1.1.     At a closing (the "Base Closing") to occur on September 24,
               1998, or, if a filing is required to be made under the HSR
               Act or rules, within five business days after any applicable
               waiting periods under the HSR Act or rules shall have
               terminated or expired, AHP shall purchase from AMBI, and AMBI
               shall issue to AHP, 3,478,261 shares of common stock (the
               "Base Shares").

         1.1.2.     The purchase price for the Base Shares shall be $4,000,000,
               and shall be paid by AHP at the Base Closing by wire transfer
               against the delivery by AMBI to AHP of the certificates which
               represent the Base Shares and the opinion of AMBI's counsel
               to the effect that the Base Shares are duly authorized,
               validly issued, fully paid and nonassessable, and free and
               clear from any liens or encumbrances of any kind (except
               restrictions from transfer as set forth in applicable
               securities laws).


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         1.1.3.     The Base Closing shall occur at the offices of AMBI. At such
               Closing, each of AMBI and AHP shall deliver to the other
               party, a certificate by an officer of each company (whose
               incumbency is verified by the Corporate Secretary or an
               Assistant Secretary) certifying that each of the
               representations and warranties (other than with respect to
               the number of shares issued and outstanding in the
               capitalization) are true and correct as of the date of such
               Closing and that all covenants required to be performed in
               this Agreement have been performed in all material respects
               by each such party.

     1.2. Additional Purchases.

         1.2.1.     At a closing (each, an "Additional Closing," with any of the
               "Base Closing" or Additional Closing being referred to herein
               as a "Closing") to occur at the offices of AMBI concurrently
               with the execution of each of the first three licenses for
               any one or more Option Products or Additional Products, as
               provided in Section 12.2 of the Product Agreement, AHP shall
               purchase from AMBI, and AMBI shall issue to AHP, a number of
               additional shares of common stock equal to $(***) divided by
               (***)% of the average of the closing prices of a share of
               common stock on NASDAQ on each of the 10 trading days up to
               and including the date which is 5 trading days immediately
               preceding such Additional Closing. In addition, as provided
               in Section 7.2 of the Product Agreement, AHP may make certain
               purchases of additional shares of AMBI common stock, the
               number of additional shares of common stock of each purchase
               being equal to $(***) divided by (***)% of the average of the
               closing prices of a share of common stock on NASDAQ during
               the 10 trading days up to and including the date which is 5
               trading days immediately preceding such Additional Closing.
               The shares of common stock to be purchased by AHP at each
               Additional Closing are referred to herein as the "License
               Shares."

         1.2.2.     The purchase price for the License Shares purchased at each
               Additional Closing shall be $(***), and shall be paid by AHP
               at such Additional Closing by wire transfer against the
               delivery by AMBI to AHP of the certificates which represent
               the License Shares purchased at such Additional Closing and
               the opinion of AMBI's counsel to the effect that the License
               Shares are duly authorized, validly issued, fully paid and
               nonassessable, and free and clear from any liens or
               encumbrances of any kind (except restrictions from transfer
               as set forth in applicable securities laws). At such Closing,
               each of AMBI and AHP shall deliver to the other party, a
               certificate by an officer of each company (whose incumbency
               is verified by the Corporate Secretary or an Assistant
               Secretary) certifying that each of the representations and
               warranties (other than with respect to the number of shares
               issued and outstanding in the capitalization) are true and
               correct as of the date of such Closing and that all covenants
               required to be 


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               performed in this Agreement have been performed in all material 
               respects by each such party.

         1.2.3.     By way of example, if on any day AHP executes two licenses
               for Option Products, AHP shall in connection therewith
               purchase common stock for an aggregate purchase price of
               $(***).

         1.2.4.     In the event that the common stock of AMBI is not traded on
               NASDAQ during the period or periods set forth in this Article
               1, the fair market price on each such day shall be determined
               to be the average bid and asked price on each such day that
               the common stock is traded on the over-the-counter bulletin
               board, or if not so traded, as determined in good faith by
               the Board of Directors of AMBI.

     1.3. Hart-Scott-Rodino

         1.3.1.     Prior to the effectuation and as a condition to any Closing
               under this Agreement, AHP shall have: (i) valued its holdings
               of AMBI stock and assets and any stock to be acquired at less
               than $15 million in accordance with Title II of the U.S.
               Hart-Scott-Rodino Antitrust Improvements Act of 1976, as
               amended and the rules promulgated thereunder (16 C.F.R.
               ss.ss.801.1 et seq.); or (ii) determined that no such filing
               is required to be made under the HSR Act or rules; provided,
               however, that in the event that AHP has determined that a
               filing under the HSR Act and rules is required, AMBI and AHP
               shall promptly make all required filings under the HSR Act
               and rules, and shall not effect any Closing hereunder until
               any applicable waiting periods under the HSR Act or rules
               shall have terminated or expired.

2.   Representations And Warranties of AMBI. AMBI represents and warrants to
     AHP that the following statements are true and correct:

     2.1. Organization and Qualification. AMBI is a corporation duly
          organized, validly existing and in good standing under the laws of
          the State of New York and has corporate power to carry on its
          business as it is now being conducted. The character of AMBI's
          properties owned or held under lease and the nature of its
          activities does not make it necessary that AMBI qualify to do
          business in any foreign jurisdiction.

     2.2. Capitalization. The authorized capital stock of AMBI consists of
          65,000,000 shares of Common Stock, par value $.005 per share, and
          5,000,000 shares of Preferred Stock $.01 par value per share. AMBI
          does not have any outstanding securities convertible into or
          exchangeable or exercisable for any shares of the capital stock of
          AMBI, nor are there outstanding any rights to subscribe for or to
          purchase, or any agreements providing for the issuance (contingent
          or otherwise) of, or any options, warrants, calls, commitments,
          understandings, arrangements or claims of any character relating
          to, the capital stock of AMBI or any securities 


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          convertible into or exchangeable or exercisable for any shares of 
          the capital stock of AMBI. As of September 15, 1998, 21,193,726 
          shares of AMBI Common Stock, 222 shares of Series C Preferred Stock, 
          and 19,750 shares of Series D Preferred Stock are validly issued and
          outstanding, fully paid and nonassessable and free of preemptive
          rights. All of the shares of AMBI Stock issuable in accordance
          with this Agreement will be, when so issued, duly authorized,
          validly issued, fully paid and nonassessable and free of
          preemptive rights, and free and clear from any liens or
          encumbrances of any kind (except restrictions from transfer as set
          forth in applicable securities laws).

     2.3. Authority Relative to This Agreement.

         2.3.1.     AMBI has the corporate power to enter into this Agreement 
               and to carry out its obligations hereunder. The execution and
               delivery of this Agreement, the performance by AMBI of its
               obligations hereunder and the consummation of the
               transactions contemplated hereby have been duly authorized by
               AMBI's Board of Directors in all material respects; the
               issuance of the shares of AMBI Stock pursuant to this
               Agreement have been duly authorized by AMBI's Board of
               Directors; and no other corporate proceedings on the part of
               AMBI are necessary to authorize this Agreement and the
               transactions contemplated hereby.

         2.3.2.     This Agreement has been executed and delivered by AMBI and
               (assuming the valid authorization, execution and delivery of
               this Agreement by AHP) is a valid and binding obligation of
               AMBI enforceable against AMBI in accordance with its terms,
               except as may be limited by or subject to any bankruptcy,
               insolvency, reorganization, moratorium or other similar laws
               affecting the enforcement of creditors' rights generally, and
               subject to general principles of equity. No filing or
               registration with, or authorization, consent or approval of,
               any public body or authority is necessary for the
               consummation by AMBI and its subsidiaries of the transactions
               contemplated by this Agreement.

         2.3.3.     No notice to or filing with, and no authorization, consent 
               or approval of, any domestic or foreign court or any public or
               governmental body or authority is necessary for the
               consummation by AMBI of the transactions contemplated by this
               Agreement (except as may be required by the HSR Act), except
               for notices or filings the failure to give or make, and
               authorizations, consents and approvals the failure to obtain,
               would not materially and adversely affect the ability of AMBI
               to consummate the transactions contemplated hereby, or the
               future conduct of the AMBI's business.

         2.3.4.     Neither the execution and delivery of, nor the consummation
               of the transactions contemplated by, this Agreement will
               result in any of the following:


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              2.3.4.1.     a default or an event that, with notice or lapse of
                      time, or both, would constitute a default, breach or
                      violation of the charter, bylaws or other governing
                      instruments of AMBI, or any material contract,
                      agreement, license or instrument to which AMBI is a
                      party or by which AMBI or its property is bound;

              2.3.4.2.     an event that would permit any Person to terminate
                      any material contract, agreement, license or
                      instrument to which AMBI is a party or by which AMBI
                      or its property is bound, or to accelerate the
                      maturity of any indebtedness or other material
                      obligation of AMBI;

              2.3.4.3.     the creation or imposition of any lien, mortgage, 
                      pledge, charge or encumbrance of any kind upon any 
                      material asset of AMBI;

              2.3.4.4.     a violation or breach of any statute, ordinance, rule
                      or regulation in any material respect applicable to
                      AMBI, or any writ, injunction or decree of any court
                      or governmental instrumentality to which AMBI is a
                      party or by which it or any of its properties are
                      bound; or

              2.3.4.5.     a loss or adverse modification under the terms
                      thereof, of any material license, franchise or other
                      authorization granted to or otherwise held by AMBI.

     2.4. Reports and Financial Statements. AMBI has filed all required
          reports and other filings with the Securities and Exchange
          Commission (the "Commission") and all such filings complied in all
          material respects with all applicable requirements of the
          Securities Act of 1933, as amended, and the rules and regulations
          thereunder (the "Securities Act") and/or the Securities Exchange
          Act of 1934, as amended, and the rules and regulations thereunder
          (the "Exchange Act"). As of their respective dates, such reports,
          statements and other written materials did not contain any untrue
          statement of a material fact or omit to state a material fact
          required to be stated therein or necessary to make the statements
          therein, in light of the circumstances under which they were made,
          not misleading. The audited statements and any unaudited interim
          financial statements of AMBI included in such reports have been
          prepared in accordance with generally accepted accounting
          principles applied on a consistent basis and fairly present the
          financial position of AMBI and its subsidiaries as at the dates
          thereof and the results of their operations and changes in
          financial position for the periods then ended, except as indicated
          therein or in the notes thereto.

     2.5. No Material Adverse Change. Since March 31, 1998, as of which date
          the AMBI filed its most recent report on Form 10-Q, there has not
          been any material adverse change in the financial condition,
          results of operations, businesses, properties, assets or
          liabilities of AMBI taken as a whole.


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     2.6. Fees, Commissions and Expenses. AMBI has not paid or agreed to
          pay, nor has it received any claims with respect to, any brokerage
          commissions, finders' fees or similar compensation in connection
          with the transactions contemplated by this Agreement.

     2.7. Investment Company Act. AMBI is not, and after giving effect to
          the transactions described herein will not be, an "investment
          company" as such term is defined in the Investment Company Act of
          1940, as amended.

3.   Representations And Warranties Of AHP. AHP represents and warrants to
     AMBI that the following statements are true and correct in all material
     respects:

     3.1. Organization and Qualification. AHP is a duly organized, validly
          existing and in good standing Delaware corporation, and has
          corporate power to carry on its business as it is now being
          conducted.

     3.2. Authority Relative to this Agreement.

         3.2.1.     AHP has the corporate power to enter into this Agreement and
               to carry out its obligations hereunder. The execution and
               delivery of this Agreement, the performance by AHP of its
               obligations hereunder and the consummation of the
               transactions contemplated hereby have been duly authorized
               and no other corporate proceedings on the part of AHP are
               necessary to authorize this Agreement and the transactions
               contemplated hereby. This Agreement has been executed and
               delivered by the AHP and (assuming the valid authorization,
               execution and delivery of this Agreement by AMBI) is a valid
               and binding obligation of AHP enforceable against AHP in
               accordance with its terms, except as may be limited by or
               subject to any bankruptcy, insolvency, reorganization,
               moratorium or other similar laws affecting the enforcement of
               creditors' rights generally, and subject to general
               principles of equity. Except as referred to herein, no filing
               or registration with, or authorization, consent or approval
               of, any public body or authority is necessary for the
               consummation by AHP of the transactions contemplated herein.

         3.2.2.     Neither the execution and delivery of, nor the consummation
               of the transactions contemplated by, this Agreement will
               result in any of the following:

              3.2.2.1.     a default or an event that, with notice or lapse of
                      time, or both, would constitute a default, breach or
                      violation of the charter, bylaws or other governing
                      instruments of AHP, or any material contract,
                      agreement, license or instrument to which AHP is a
                      party or by which AHP, or the property of AHP is
                      bound;

              3.2.2.2.     an event that would permit any Person to terminate
                      any material contract, agreement, license or
                      instrument to which AHP is a 


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                      party or by which AHP is bound, or to accelerate the 
                      maturity of any indebtedness or other obligation of AHP;

              3.2.2.3.     the creation or imposition of any lien, mortgage, 
                      pledge, charge or encumbrance of any kind upon any 
                      material asset of AHP;

              3.2.2.4.     a violation or breach of any statute, ordinance, rule
                      or regulation in any material respect applicable to
                      AHP , or any writ, injunction or decree of any court
                      or governmental instrumentality to which AHP is a
                      party or by which AHP, or the property of AHP is
                      bound; or

              3.2.2.5.     a loss or adverse modification under the terms
                      thereof, of any material license, franchise or other
                      authorization granted to or otherwise held by AHP.

     3.3. Fees, Commissions and Expenses. Neither AHP nor any of its
          affiliates has paid or agreed to pay, nor has it received any
          claims with respect to, any brokerage commissions, finders' fees
          or similar compensation in connection with the transactions
          contemplated by this Agreement.

     3.4. Investment Representations.

         3.4.1.     The AMBI Stock may be sold or otherwise transferred only if
               registered under the Securities Act, pursuant to an exemption
               therefrom as indicated in an opinion of counsel supplied by
               AHP reasonably acceptable to AMBI and its counsel, or with
               the favorable opinion of counsel to AMBI to the effect that
               such sale or other transfer may be made in the absence of
               registration under the Securities Act. The certificates
               representing the AMBI Stock will be legended to reflect this
               restriction, and stop transfer instructions will apply.

         3.4.2.     AHP represents and warrants that it is purchasing the common
               stock solely for investment solely for its own account and
               not with a view to or for the resale or distribution thereof
               except as permitted under a Registration Statement or as
               otherwise permitted under the Securities Act.

4.   Rule 144 Current Information. AMBI shall timely file periodic reports
     under the Exchange Act to the end that AMBI shall satisfy the
     requirements of Rule 144 in relation to the availability of current
     public information with respect to AMBI.

5.   Participation Registration Rights.

     5.1. If AMBI shall at any time propose the registration under the
          Securities Act of any shares of common stock, AMBI shall give
          notice as promptly as possible (but no less than 10 days before
          filing a registration statement with respect to such registration)
          of such proposed registration to AHP, and AMBI at its sole expense


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          (except with respect to any underwriting discount) shall use its
          best efforts to cause such number of Common Shares as AHP shall
          request within 10 days after the receipt of such notice to be
          included in any such offering; provided, however, that

         5.1.1.     AMBI shall not be required to give notice or include such
               shares in any such registration which is (A) a registration
               of a stock option or compensation plan or of securities
               issued or issuable pursuant to any such plan, or (B) a
               registration of securities proposed to be issued in exchange
               for securities or assets of, or in connection with a merger
               or consolidation with, another corporation;

         5.1.2.     AMBI shall not be required to include such shares in any 
               such registration if AMBI is advised in writing by its investment
               banking firm that the inclusion of such shares would in its
               opinion have a materially adverse effect on such proposed
               offering of its common stock, provided, however, that such
               exclusion shall be made in proportion to the number of shares
               proposed to be included in such offering other than by AMBI,
               and in no case shall such exclusion be more than 10% of the
               total number of shares proposed to be sold in any such
               offering; and

     5.2. AMBI may, without the consent of AHP, withdraw such registration
          statement and abandon the proposed offering in which AHP had
          requested to participate.

     5.3. AMBI shall supply to AHP a reasonable number of copies of all
          registration materials and prospectuses. AMBI and AHP shall
          execute and deliver to each other indemnity agreements which are
          conventional in registered offerings of this type, indemnifying
          AHP for any and all liabilities relating to any registration
          statement, other than based upon information supplied by AHP
          specifically for use therein, and in no case shall AHP's liability
          exceed the proceeds of the sale to AHP under any such offering or
          registration. AHP shall reasonably cooperate with AMBI in the
          preparation and filing of the Registration Statement and
          appropriate amendments thereto, and shall provide to AMBI such
          information with respect to the AHP as AMBI may reasonably require
          in connection therewith.

     5.4. AHP's rights under this Section 5 shall terminate on the later of
          (i) 5 years from the date of this Agreement, or (ii) after AHP
          owns less than 5% of the outstanding common stock of AMBI and is
          free to sell all shares it owns under Rule 144 (k) of the
          Securities Act or any successor provision thereof.

6.   General Provisions

     6.1. Survival of Representations and Warranties. All representations
          and warranties made hereunder shall survive the Closing until
          September 30, 1999, or 12 months from the last Closing in which a
          certificate with respect to the representations and warranties is
          made hereunder, as the case may be.


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     6.2. Notices. All notices and other communications hereunder shall be
          in writing and shall be deemed given if three days after being
          mailed by registered or certified mail (return receipt requested,
          postage prepaid) or if delivered personally to the parties at the
          following addresses (or at such other address for a party as shall
          be specified by like notice):

                  If to AMBI, to:

                  AMBI Inc.
                  771 Old Saw Mill Road
                  Tarrytown, NY 10591
                  Attention: Senior Vice President & General Counsel

                  with a copy to:

                  Oscar D. Folger, Esq.
                  Law Offices of Oscar D. Folger
                  521 Fifth Avenue
                  New York, NY 10175

                  if to AHP, to:

                  American Home Products Corporation
                  Five Giralda Farms
                  Madison, NJ 07940
                  Attention: Treasurer

                  with a copy to:

                  American Home Products Corporation
                  Five Giralda Farms
                  Madison, NJ 07940
                  Attention: Senior Vice President and General Counsel

7  Miscellaneous. This Agreement (including the documents and instruments
   referred to herein) (a) constitutes the entire agreement and supersedes
   all other prior agreements and understandings, both written and oral,
   among the parties, or any of them, with respect to the subject matter
   hereof; (b) inures to the benefit of the parties hereto and their
   respective permitted representatives and assigns; (c) shall not be
   assigned by operation of law or otherwise; and (d) shall be governed in
   all respects, including validity, interpretation and effect, by the laws
   of the State of New York (without giving effect to the provisions thereof
   relating to conflicts of law). This Agreement may be executed in two or
   more counterparts which together constitute a single agreement.



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8  Publicity. Neither party shall issue any press releases which make
   references to the other without the consent of the other party, which
   consent shall not unreasonably withheld. Each party shall therefore
   provide the other with draft press releases for review and comment. Each
   party agrees to review and comment promptly on draft press releases
   received from the other party.

         IN WITNESS WHEREOF, AMBI and AHP have caused this Agreement to be
signed by their respective officers thereunto duly authorized all as of the
date first written above.

AMBI INC.

By: /s/ Fredric D. Price
    ---------------------------------

Name:  Fredric D. Price
       ------------------------------

Title: President & CEO
       ------------------------------

AMERICAN HOME PRODUCTS CORPORATION

By: /s/ Gerald A. Jibilian
    ---------------------------------

Name: Gerald A. Jibilian
      -------------------------------

Title: Vice President
       ------------------------------