<PAGE>


EXHIBIT 10.20

                              AMENDMENT AND WAIVER
                                       TO
                                CREDIT AGREEMENT


        AMENDMENT AND WAIVER, dated as of June 26, 2007 (the "Amendment") to the
Credit Agreement, dated as of May 10, 2002 (as amended, the "Agreement"), by and
between ACETO CORPORATION, a New York corporation, ACETO AGRICULTURAL CHEMICALS
CORPORATION, a New York corporation, CDC PRODUCTS CORPORATION, a New York
corporation, ACETO SANITARY CORP. F/K/A MAGNUM RESEARCH CORP., a New York
corporation, ACCI REALTY CORP., a New York corporation, LARLABS CORP., a New
York corporation, ARSYNCO INC., a New Jersey corporation, ROEHR CHEMICALS, INC.,
a New York corporation, ACETO INDUSTRIAL CHEMICAL CORP., a New York corporation,
jointly and severally (each a "Company" and, collectively, the "Companies") and
JPMORGAN CHASE BANK, N.A., a national banking association, successor to JPMorgan
Chase Bank (the "Lender").

                                    RECITALS

        The Company has requested certain amendments and a waiver as set forth
herein and the Lender has agreed to such amendments and waiver subject to the
terms and conditions of this AMENDMENT.

        NOW, THEREFORE, the parties hereto hereby agree as follows:


                                   ARTICLE 1.
                         AMENDMENTS TO CREDIT AGREEMENT

        SECTION 1.1. Section 1.01 is hereby amended to add the following defined
term immediately following the defined term "Quoted Rate Loans" therein.

        "RCP Joint Venture" shall mean UPI - Aceto LLC, a domestic limited
liability company formed for the purpose of buying and marketing an
Environmental Protection Agency regulated crop protection product of which (i)
the Aceto or its Subsidiaries own directly or indirectly at least 49.5% of the
membership interest of such entity, (ii) United Phosphorous Inc. owns not more
than 50.5% of the membership interests of such entity, and (iii) the allocated
profits, losses and capital requirements of such entity are allocated one half
to each of Aceto or its Subsidiaries and to United Phosphorous Inc.


<PAGE>


        SECTION 1.2. The definition of "Revolving Credit Commitment Termination
Date" in Section 1.01 of the Agreement is hereby amended to delete the date
"June 30, 2007" and to insert the date "June 30, 2010" in place thereof.

        SECTION 1.3. Section 7.06 of the Agreement is hereby further amended to
delete the word "and" prior to clause (h) therein and to add the following text
at the end of clause (h):

                and (i) loans and investments by Aceto or its Subsidiaries to
                and in the RCP Joint Venture provided; (i) no Default or Event
                of Default should have occurred and be continuing on the date of
                any such loan or investment (ii) the initial investment or loan
                shall have occurred on or prior to September 30, 2007, and (iii)
                such loans and investments shall not exceed $5,100,000 in the
                aggregate at any time outstanding.

        SECTION 1.4. Section 7.13(a) of the Agreement is hereby amended to
delete the amount "$72,000,000" and to insert the amount "$100,000,000" in place
thereof in each instance.

        SECTION 1.5. Section 7.14 of the Agreement is hereby amended to delete
the text "not in excess of $4,500,000 in the aggregate" in clause (a)(i)
thereof.

        SECTION 1.6. Section 7.14 of the Agreement is hereby further amended to
delete the dollar amount "$7,000,000" in clause (a)(ii) thereof and to insert
the dollar amount "$10,000,000" in place thereof.

        SECTION 1.7. Schedules I, II, III, IV, V, VI, VII and VIII are hereby
amended and restated in their entirety as set forth as Schedules I, II, III, IV,
V, VI, VII and VIII to this Amendment.


                                   ARTICLE 2.
                           WAIVER TO CREDIT AGREEMENT

        SECTION 2.1. Compliance with Section 6.13 of the Agreement is hereby
waived with respect to the Companies' failure to timely execute a Joinder
Agreement and to provide the other documentation required thereunder with
respect to Aceto Pharma Corp.

                                       2
<PAGE>


                                   ARTICLE 3.
                         REPRESENTATIONS AND WARRANTIES

        The Companies hereby represent and warrant to the Lender that:

        SECTION 3.1. Each of the representations and warranties set forth in
each Loan Document is true and correct is all material respects as of the date
hereof with respect to the Companies, with the same effect as though made on the
date hereof (unless any such representation and warranty is as of a specific
date, in which event, as of such date), and is hereby incorporated herein in
full by reference as if fully restated herein in its entirety.

        SECTION 3.2. As of the date hereof, and after giving effect to the terms
hereof, and all prior waivers and amendments executed by the Lender and the
Companies prior to the date hereof , there exists no Default or Event of
Default.

        SECTION 3.3. The Companies have the corporate power and authority to
enter into, perform and deliver this Amendment and any other documents,
instruments, agreements or other writings to be delivered in connection
herewith. This Amendment and all documents contemplated hereby or delivered in
connection herewith, have each been duly authorized, executed and delivered and
the transactions contemplated herein have been duly authorized.

        SECTION 3.4. This Amendment and any other documents, agreements or
instruments now or hereafter executed and delivered to the Lender by the
Companies in connection herewith constitute (or shall, when delivered,
constitute) valid and legally binding obligations of Companies, each of which is
and shall be enforceable against Companies in accordance with their respective
terms.

        SECTION 3.5. No consent, waiver or approval of any entity is or will be
required in connection with the execution, delivery, performance, validity or
enforcement of this Amendment, or any other agreements, instruments or documents
to be executed and/or delivered in connection herewith or pursuant hereto.

        SECTION 3.6. Each of the Loan Documents to which it is a party and each
lien and security interest granted thereunder is in full force and effect and
will remain in full force and effect after giving effect to this Amendment.

        SECTION 3.7. Neither the certificate of incorporation nor the bylaws or
other organizational documents of any Company has been amended since June 1,
2004.

                                       3
<PAGE>


                                   ARTICLE 4.
                           CONDITIONS TO EFFECTIVENESS

        SECTION 4.1. The amendments and waivers provided herein shall not be
effective unless the Lender shall have received on or prior to the date hereof
the following:

                (a)     a Joinder Agreement dated the date hereof in the form
                        attached hereto as Annex I duly executed by the
                        Companies and Aceto Pharma Corp.

                (b)     a Secretary's Certificate dated the date hereof in the
                        form attached hereto as Annex II duly executed by the
                        officers of Aceto Pharma Corp. identified therein.

                (c)     payment of a nonrefundable amendment and waiver fee in
                        the amount of $15,000.

                (d)     reimbursement of the reasonable legal fees and expenses
                        of Farrell Fritz, P.C. counsel to the Lender, in the
                        amount of $2,900.

                                   ARTICLE 5.
                                  MISCELLANEOUS

        SECTION 5.1. This Amendment may be executed in any number of
counterparts, all of which taken together shall constitute one and the same
instrument, and any party hereto may execute this Amendment by signing any such
counterpart.

        SECTION 5.2. THIS AMENDMENT SHALL BE GOVERNED BY, AND INTERPRETED AND
CONSTRUED IN ACCORDANCE WITH, THE LAWS OF THE STATE OF NEW YORK (WITHOUT GIVING
EFFECT TO THE CONFLICT OF LAWS PROVISIONS THEREOF).

        SECTION 5.3. On and after the effective date of this Amendment, each
reference in the Agreement to "this Agreement", "hereunder", "hereof" or words
of like import referring to the Agreement, and each reference in the Loan
Documents to "the Agreement", "thereunder", "thereof", or words of like import
referring to the Agreement, shall mean and be a reference to the Agreement as
amended by this Amendment. The Agreement, as amended by this Amendment, is and
shall continue to be in full force and effect and is hereby in all respects
ratified and confirmed. This Amendment shall constitute a "Loan Document".

        SECTION 5.4. The Companies agree to take such further actions as the
Lender shall reasonably request in connection herewith to evidence the
amendments herein contained to the Agreement.

                                       4
<PAGE>


        IN WITNESS WHEREOF, the Companies and the Lender have caused this
Amendment to be duly executed as of the day and year first above written.


                                                 ACETO CORPORATION


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  Chief Executive Officer

                                                 ACETO AGRICULTURAL CHEMICALS
                                                 CORPORATION


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  Director

                                                 CDC PRODUCTS CORPORATION


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  Director

                                                 ACETO SANITARY CORP.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President

                                                 ACCI REALTY CORP.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President


                                       5
<PAGE>



                                                 LARLABS CORP.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President

                                                 ARSYNCO INC.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  Chairman

                                                 ROEHR CHEMICALS, INC.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President

                                                 ACETO INDUSTRIAL CHEMICAL CORP.


                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President


                                                 JPMORGAN CHASE BANK, N.A.


                                                 By: /s/ Sanford Wald
                                                 ------------------------
                                                 Name:   Sanford Wald
                                                 Title:  Vice President


                                       6
<PAGE>


                                                                         ANNEX I

                                JOINDER AGREEMENT


        Reference is made to that certain Credit Agreement, dated as of May 10,
2002, by and between ACETO CORPORATION, a New York corporation, ACETO
AGRICULTURAL CHEMICALS CORPORATION, a New York corporation, CDC PRODUCTS
CORPORATION, a New York corporation, ACETO SANITARY CORP., a New York
corporation, ACCI REALTY CORP., a New York corporation, LARLABS CORP., a New
York corporation, ARSYNCO INC., a New Jersey corporation, ROEHR CHEMICALS, INC.,
a New York corporation, ACETO INDUSTRIAL CHEMICAL CORP., a New York corporation,
jointly and severally (each a "Company" and, collectively, the "Companies") and
JPMORGAN CHASE BANK, N.A., a national banking association, successor to JPMorgan
Chase Bank (the "Lender") (as same has been and may be further amended,
restated, supplemented or otherwise modified, from time to time, the "Credit
Agreement").

        ACETO PHARMA CORP., a Delaware corporation (the "New Company") hereby
acknowledges and agrees that from and after, the date hereof, (i) the New
Company shall be and become (a) a Company under, and in accordance with and
subject to, the Credit Agreement and Company shall be bound by the terms of the
Credit Agreement; (ii) the New Company shall perform in accordance with the
terms of the Credit Agreement and any other Loan Documents to which it is a
party; (iii) the New Company shall be jointly and severally liable with the
Companies for all of its Obligations including, without limitation, those
incurred prior to the date hereof; and (iv) the New Company hereby joins in
making each of the representations, warranties, covenants and agreements of the
Companies set forth in the Credit Agreement, as if it were originally named a
Company therein, as of the date hereof.

        The New Company agrees to execute and deliver such documents and
instruments as the Lender may request from time to time to further evidence the
agreements of the New Company herein.

        The New Company hereby represents and warrants to the Lender as follows:

        1.      The New Company is duly organized, validly existing and in good
standing under the laws of its jurisdiction of incorporation, has the corporate
power to own its assets and to transact the business in which it is presently
engaged.

        2.      The New Company has the corporate power, authority and legal
right to make, deliver, and perform this Joinder Agreement, has taken all
necessary corporate action to authorize execution, delivery, performance of this
Joinder Agreement. No consent of any other person, no consent, license, permit,
approval or authorization of, exemption by, notice or report to, or
registration, filing or declaration with, any governmental authority is required
in connection with the execution, delivery, performance and validity or
enforceability of this Joinder Agreement.

                                       7
<PAGE>


        3.      There is no litigation, investigation or other proceeding of or
before any arbitrator or governmental authority pending or threatened against
the New Company or any of its assets, which, if adversely determined, would have
a material adverse effect on the business, assets or financial condition of the
New Company.

        4.      This Joinder Agreement has been duly executed and delivered on
behalf of the New Company and constitutes the legal, valid and binding
obligation of the New Company enforceable against the New Company in accordance
with its terms except as enforcement may be limited by applicable bankruptcy,
insolvency, reorganization, moratorium, or similar laws affecting the
enforcement of creditors' rights generally.

        5.      The New Company has reviewed the Credit Agreement and agrees to
be bound by the terms and conditions thereof.

        All capitalized terms used in this Joinder Agreement and not otherwise
defined herein shall have the meaning set forth thereof included in the Credit
Agreement.

        THIS JOINDER AGREEMENT SHALL BE CONSTRUED IN ACCORDANCE WITH THE LAWS OF
THE STATE OF NEW YORK, WITHOUT REFERENCE TO PRINCIPLES OF CONFLICTS OF LAW.

                          [NEXT PAGE IS SIGNATURE PAGE]



                                       8
<PAGE>


        IN WITNESS WHEREOF, the undersigned have executed this Joinder Agreement
as of the 26 day of June, 2007.

                                                 ACETO PHARMA CORP.

                                                 By: /s/ Leonard Schwartz
                                                 ------------------------
                                                 Name:   Leonard Schwartz
                                                 Title:  President

ACKNOWLEDGED AND AGREED:

ACETO CORPORATION


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  Chief Executive Officer

ACETO AGRICULTURAL CHEMICALS CORPORATION


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  Director

CDC PRODUCTS CORPORATION


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  Director

ACETO SANITARY CORP.


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  President

ACCI REALTY CORP.


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  President

                                       9
<PAGE>


LARLABS CORP.

By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  President

ARSYNCO INC.


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  Chairman

ROEHR CHEMICALS, INC.


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  President

ACETO INDUSTRIAL CHEMICAL CORP.


By: /s/ Leonard Schwartz
------------------------
Name:   Leonard Schwartz
Title:  President


JPMORGAN CHASE BANK, N.A.


By: /s/ Sanford Wald
--------------------
Name:  Sanford Wald
Title: Vice President



                                       10
<PAGE>


                                                                        ANNEX II

                             SECRETARY'S CERTIFICATE


        I, Douglas Roth, the duly elected Secretary of Aceto Pharma Corp., a
Delaware corporation (the "Company"), do hereby certify as follows:

        1.      Attached hereto as Exhibit A is a true, correct and complete
copy of the certificate of incorporation of the Company as in effect as of the
date hereof together with any amendments thereto. I know of no plan or
proceeding for the dissolution or liquidation of the Company.

        2.      Attached hereto as Exhibit B is a true, correct and complete
copy of the by-laws of the Company as in effect as of the date of adoption of
the resolutions set forth below and as of the date hereof.

        3.      Attached hereto as Exhibit C is a true, correct and complete
copy of resolutions duly adopted by the Board of Directors of the Company. Such
resolutions have not been amended, modified, revoked or rescinded as of the date
hereof, are in full force and effect and are the only resolutions adopted by the
Board of Directors of the Company with respect to the subject matter thereof.

        4.      The below named persons are duly elected and qualified officers
of the Company holding the respective offices set forth opposite their names and
the signatures set forth opposite their names are their genuine signatures:

         Name                       Office              Signature
         ----                       ------              ---------

         Leonard Schwartz           President           /s/ Leonard Schwartz


        5.      The Certificate of Incorporation and the By-laws have not been
amended since the date of their certification.



                                       11
<PAGE>



        IN WITNESS WHEREOF, I have signed this Certificate as of the 26 day of
June, 2007.

                                                     /s/ Douglas Roth
                                                     ----------------
                                                     Secretary

        THE UNDERSIGNED hereby confirms that Douglas Roth has been duly elected,
was duly qualified and on the date hereof is the Secretary of the Company and
that the signature above is his genuine signature.

                                                     /s/ Leonard Schwartz
                                                     --------------------
                                                     President


                                       12
<PAGE>


                                                                       EXHIBIT C


                   RESOLUTIONS ADOPTED AT A SPECIAL MEETING OF
                            THE BOARD OF DIRECTORS OF
                               ACETO PHARMA CORP.


RESOLVED THAT

        1.      That the President is hereby authorized from time to time on
behalf of Aceto Pharma Corp. (the "Company"):

        (a)     To borrow money and obtain credit and other financial
                accommodations for or on behalf of the Company at any time, and
                from time to time, from JPMorgan Chase Bank, N.A. (the "Bank")
                pursuant to a Credit Agreement (the "Credit Agreement") among
                the Bank, Aceto Corporation, Aceto Agricultural Chemicals
                Corporation, CDC Products Corporation, Aceto Sanitary Corp.
                f/k/a Magnum Research Corp., ACCI Realty Corp, Arsynco Inc.,
                Roehr Chemicals, Inc., and Aceto Industrial Chemical Corp., a
                New York corporation (excluding the Company, collectively, the
                "Other Borrowers") and the company;

        (b)     To guarantee to the Bank the payment and performance of all
                obligations and liabilities of the Other Borrowers to the Bank,
                whether now existing or hereafter incurred, upon terms and
                conditions satisfactory to the Bank;

        (c)     To apply for letters of credit or engage in acceptance
                financing;

        (d)     To pledge, grant a security interest in, assign, endorse,
                negotiate, deliver or otherwise hypothecate or transfer to the
                Bank any and all assets now or hereafter held, owned or
                controlled by the Company as security for any loan, credit or
                financial accommodation from the Bank to the Company;

        (e)     To execute and deliver in the name of the Company any agreement
                or agreements, including, but not limited to a Joinder to the
                Credit Agreement (collectively, the "Agreements") with the Bank
                with respect to financial or credit accommodations to the
                Company and the Other Borrowers with such changes, additions and
                deletions to the Agreements agreed to by any such officer, which
                execution and delivery shall be deemed conclusive evidence of
                the approval by the Company of the terms and agreements thereof;

        (f)     To make, execute and deliver to the Bank any and all financing
                statements, consents, certificates, documents, instruments, and
                assignments, including, but not limited to, schedules,
                endorsements, guarantees, indemnities, agreements, waivers,
                amendments, consents, notices or other instruments as may be

                                       13
<PAGE>


                required by the Bank, from time to time, in connection with or
                in furtherance of the Agreements or any other transactions; and

        (g)     To do and perform all other acts and things from time to time
                deemed by any officer or agent of the Bank or other person
                designated by any of them, necessary, convenience or proper to
                carry out, modify or supplement the Agreements or to fully carry
                out the intent of this resolution, and the execution, delivery
                or performance thereof by such officer or officers of the
                Company shall be deemed conclusive evidence of the approval
                thereof by the Company.

        2.      That the Secretary be and hereby is authorized and directed to
certify to the Bank the names of the present officers of the Company and persons
authorized to sign for it, and the offices respectively held by them, together
with specimens of their signatures.

        3.      That the Secretary be and hereby is authorized and directed to
certify to the Bank that this resolution has been duly adopted, is in full force
and is in accordance with the provisions of the charter and by-laws of the
Company.

        4.      That any other transactions heretofore made on behalf of the
Company with the Bank be and hereby are ratified, confirmed and approved, and
that the Bank are hereby authorized to rely upon the authority conferred by this
Resolution.





                                       14