EXHIBIT 99.4


                   SECOND AMENDMENT TO SHAREHOLDERS AGREEMENT

         THIS SECOND AMENDMENT TO SHAREHOLDERS AGREEMENT (the "Second
Amendment") is dated as of June 7, 2004, among Carrizo Oil & Gas, Inc., a Texas
corporation (the "Company"), J.P. Morgan Partners (23A SBIC), LLC (formerly
known as CB Capital Investors, L.P.) ("J.P. Morgan Partners"), Mellon Ventures,
L.P., S.P. Johnson IV, Frank A. Wojtek and Steven A. Webster (the
"Shareholders"). Capitalized terms used but not otherwise defined in this
Amendment should have the meanings given such terms in the Shareholders
Agreement dated as of December 15, 1999 by and among the Company and the
Shareholders, as amended through the date hereof (the "Agreement").

                                   WITNESSETH:

         WHEREAS, the Company and the Shareholders desire to amend the Agreement
to remove Mellon Ventures, L.P., S.P. Johnson IV, Frank A. Wojtek and Steven A.
Webster as Shareholders, Original Founder Shareholders, signatories and parties
thereto;

         WHEREAS, Section 6.1 of the Agreement provides that, subject to certain
exceptions, an amendment of the provisions of the Agreement requires the prior
written consent of the Company, the Requisite Founder Shareholders and the
Requisite Investors;

         WHEREAS, the undersigned Founder Shareholders hold in excess of 50% of
the outstanding shares of Common Stock held by all Founder Shareholders as of
the date of this Amendment, and therefore qualify as the Requisite Founder
Shareholders;

         WHEREAS, the undersigned Investors hold in excess of 50% of the
outstanding shares of Common Stock held by all Investors as of the date of this
Amendment, and therefore qualify as the Requisite Investors;

         NOW, THEREFORE, the parties hereto, in consideration of the mutual
covenants and agreements hereinafter set forth and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
hereby agree as follows:

         1. Effective as of the date hereof, the Agreement is hereby amended to
delete Mellon Ventures, L.P., S.P. Johnson IV, Frank A. Wojtek and Steven A.
Webster (each, an "Exiting Shareholder") as Shareholders, Original Founder
Shareholders and Investors, as the case may be, and as signatories and parties
thereto. As a result of this Amendment, any Securities owned by an Exiting
Shareholder shall cease to be Shares, and no Exiting Shareholder shall have,
from and after the effective date of this Amendment, any rights or obligations
under the Agreement.

         2. The Company and J.P. Morgan Partners acknowledge that they remain
signatories and parties to the Agreement, J.P. Morgan Partners remains an
Investor, and the terms of the Agreement, as amended by this Second Amendment,
shall continue in full force and effect.

         3. Each of the following definitions in Section 1.1 is hereby deleted
in its entirety:


         "Additional CB Capital Director" and "Additional CB Capital Directors;"
"Business;" "Committee;" "Competitor;" "Compliance Sideletter;" "Equity
Incentive Plans;" "Excluded Securities;" "Existing Shares;" "Founder
Shareholders;" "Initial CB Capital Director" and "Initial CB Capital Directors;"
"Joinder Agreement;" "Liquidity Opportunity;" "Mellon;" "Minimum Public Float;"
"Nonvoting Securities;" "Observer;" "Offered Securities;" "Options;" "Original
Founder Shareholders;" "Permitted Transfer;" "Preemptive Offer;" "Preemptive
Offer Acceptance Notice;" "Preemptive Offer Period;" "Proportionate Percentage;"
"Refused Securities;" "Registration Rights Agreement;" "Regulated Holder;"
"Regulatory Problem;" "Requisite Founder Shareholders;" "Sale Notice;"
"Significant Shareholder;" "Tag Along Notice;" "Tansferring Shareholder;"
"Valuation Procedure;" and "Warrant Agreement."

         Each of the following definitions in Section 1.1 is hereby deleted in
its entirety and is substituted therefor with the following:

            ""CB CAPITAL" means CB Capital Investors, L.P., a Delaware limited
         partnership, and any successor thereto, including J.P. Morgan Partners
         (23A SBIC), LLC.

            "CB CAPITAL DIRECTOR" and "CB CAPITAL DIRECTORS" have the meanings
         given to such terms in Section 2.1.

            "INVESTORS" means, collectively, those persons listed on Schedule I
         attached hereto under the heading "Investors," and every other Person
         who hereafter becomes a party to this Agreement as an "Investor."

            "SHAREHOLDERS" means the holders of Common Stock and the holders of
         Common Stock Equivalents (including, without limitation, the Warrants),
         in each case, who are parties hereto, and shall include any other
         Person who hereafter becomes a party to this Agreement as a
         Shareholder."

         All other provisions and definitions contained in Section 1.1 remained
unchanged.

         4. Section 2.1 is hereby deleted in its entirety and is substituted
therefor with the following:

            "2.1 ELECTION OF DIRECTORS GENERALLY.

            (a) For so long as the CB Capital owns at least 15% of the Fully
         Diluted Capital Stock, the Company agrees, with respect to each
         shareholders meeting at which directors are elected (or action by
         written consent in lieu of an annual meeting), (i) to propose as
         nominees for election to the Board at such meeting two individuals
         designated by CB Capital (each, a "CB Capital Director"), (ii) to
         include the name of each CB Capital Director in the Company's proxy
         statement and proxy card solicited on behalf of the Board for such
         meeting, (iii) to solicit proxies on behalf of each CB Capital Director
         to the same extent proxies are solicited on behalf of any other nominee
         by the Board for election to the Board and (iv) to cause the
         attorneys-in-fact or proxies named in the applicable proxy


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         cards to vote the shares with respect to which proxies are given in the
         manner directed by such proxy cards.

            (b) For so long as the CB Capital owns at least 7 1/2% of the Fully
         Diluted Capital Stock but less than 15% of the Fully Diluted Capital
         Stock, the Company agrees, with respect to each shareholders meeting at
         which directors are elected (or action by written consent in lieu of an
         annual meeting), (i) to propose as nominee for election to the Board at
         such meeting one CB Capital Director, (ii) to include the name of the
         CB Capital Director in the Company's proxy statement and proxy card
         solicited on behalf of the Board for such meeting, (iii) to solicit
         proxies on behalf of the CB Capital Director to the same extent proxies
         are solicited on behalf of any other nominee by the Board for election
         to the Board and (iv) to cause the attorneys-in-fact or proxies named
         in the applicable proxy cards to vote the shares with respect to which
         proxies are given in the manner directed by such proxy cards.

            (c) Notwithstanding anything to the contrary contained herein, the
         Company shall not be required to propose as nominee for election or
         otherwise take action to cause the election of any Person under Article
         II or otherwise who has been removed from the Board for "cause" (as
         defined in Article 7, Section 2 of the Charter) or who the Board has
         determined could, if elected, be removed for cause as a result of prior
         actions or omissions. With respect to any determination of cause
         hereunder for which a determination is otherwise to be made by the
         Board, such determination shall require the affirmative vote of all CB
         Capital Directors other than those CB Capital Directors that the
         Company has alleged may be removed for cause."

         5. Section 2.2 is hereby deleted in its entirety.

         6. Section 2.3 is hereby deleted in its entirety.

         7. Section 2.4 is hereby deleted in its entirety.

         8. Section 2.5 is hereby deleted in its entirety and is substituted
therefor with the following:

            "2.5 VACANCIES.

            If a vacancy is created on the Board by reason of the death, removal
         or resignation of any CB Capital Director, then such vacancy may be
         filled by the remaining directors in accordance with Section 2.1."

         9. Section 2.6 is hereby deleted in its entirety.

         10. Section 2.7 is hereby deleted in its entirety.


                                      -3-

         11. Section 2.8 is hereby deleted in its entirety.

         12. Section 2.9 is hereby deleted in its entirety.

         13. Section 2.10 is hereby deleted in its entirety.

         14. Section 3.1 is hereby deleted in its entirety.

         15. Article III is hereby deleted in its entirety.

         16. Article IV is hereby deleted in its entirety.

         17. Article V is hereby deleted in its entirety.

         18. Section 6.1 is hereby deleted in its entirety and is substituted
therefor with the following:

            "6.1 AMENDMENT.

            Except as expressly set forth herein, the provisions of this
         Agreement may only be amended or waived with the prior written consent
         of the Company and the Requisite Investors."

         19. Article VII is hereby deleted in its entirety and is substituted
therefor with the following:

                             "DURATION; TERMINATION

            The provisions of this Agreement shall terminate upon the first to
         occur of (A) notice of termination by the Requisite Investors, (B) a
         Sale of the Company which has been consented to by the Requisite
         Investors and the consideration received by the Shareholders in
         connection with such sale consists solely of cash and (C) no Investor
         owns more than 7 1/2% of the Fully Diluted Common Stock."

         20. Section 8.10(b) is hereby deleted in its entirety.

         21. Section 8.13(a) is hereby deleted in its entirety.

         22. Section 8.14 is hereby deleted in its entirety.

         23. Section 8.15 is hereby deleted in its entirety.

         24. Exhibit A is hereby deleted in its entirety.

         25. Exhibit B is hereby deleted in its entirety.


                                      -4-

         26. This Amendment shall be governed by and construed in accordance
with the domestic laws of the State of New York without giving effect to any
choice or conflict of law provision or rule (whether in the State of New York or
any other jurisdiction) that would cause the application of the laws of any
jurisdiction other than the State of New York except to the extent of internal
corporate matters, which shall be governed by the provisions of the applicable
law of the State of Texas. This Amendment may be executed in any number of
counterparts, and each counterpart hereof shall be deemed to be an original
instrument, but all such counterparts together shall constitute but one
agreement.

         IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date first written above.



                                    COMPANY:

                                    Carrizo Oil & Gas, Inc.

                                      By:  /s/ Paul F. Boling
                                         ---------------------------------------
                                          Name: Paul F. Boling
                                          Title: Chief Financial Officer


                                    INVESTOR:

                                    J.P. Morgan Partners (23A SBIC), LLC

                                      By:  J.P. Morgan Partners (23A SBIC
                                           Manager), Inc., its general partner

                                           By:  /s/ Christopher Behrens
                                              ----------------------------------
                                              Name: Christopher Behrens
                                              Title: Managing Director


                                    INVESTORS PRIOR TO EFFECTIVENESS OF THIS
                                    AMENDMENT ONLY:

                                    Mellon Ventures, L.P.

                                      By:  MVMA, L.P., its general partner


                                         By: MVMA, Inc., its general partner

                                             By:  /s/ Ronald J. Coombs
                                                --------------------------------
                                                Name: Ronald J. Coombs
                                                Title: Chief Financial Officer


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                                    FOUNDER SHAREHOLDERS PRIOR TO EFFECTIVENESS
                                    OF THIS AMENDMENT ONLY:


                                    /s/ S.P. Johnson IV
                                    --------------------------------------------
                                    S.P. Johnson IV



                                    /s/ Frank A. Wojtek
                                    --------------------------------------------
                                    Frank A. Wojtek



                                    /s/ Steven A. Webster
                                    --------------------------------------------
                                    Steven A. Webster


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