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                                                                     EXHIBIT 4.4


                                 SIXTH AMENDMENT
                                       TO
              FIRST AMENDED, RESTATED, AND COMBINED LOAN AGREEMENT
                     BY AND BETWEEN CARRIZO OIL & GAS, INC.
                                AND COMPASS BANK


         This Sixth Amendment to the Loan Agreement (this "Sixth Amendment") by
and between CARRIZO OIL & GAS, INC., a Texas corporation (the "Borrower"), and
COMPASS BANK, a Texas chartered bank (the "Bank"), is entered into on this 23rd
day of April 1999, and shall be effective as of that date for all purposes.

                              W I T N E S S E T H:

         Borrower and Bank entered into a First Amended, Restated, and Combined
Loan Agreement dated August 28, 1997, as amended by the First Amendment thereto
dated December 23, 1997, the Second Amendment thereto dated December 30, 1997,
the Third Amendment thereto dated July 30, 1998, the Fourth Amendment thereto
dated September 24, 1998 and the Fifth Amendment thereto dated March 22, 1999
(collectively, the "Loan Agreement"). Capitalized terms used, but not defined
herein, shall have the meanings prescribed therefor in the Loan Agreement.

         Borrower has requested that Bank waive non-compliance with and adjust a
certain covenant in the Loan Agreement.

         NOW, THEREFORE, in consideration of the mutual promises herein
contained, and for other good and valuable consideration, the receipt and
sufficiency of which are acknowledged by Borrower and Bank, and each intending
to be legally bound hereby, the parties agree as follows:

         I. Specific Amendments to Loan Agreement.

         Article I of the Loan Agreement is hereby amended by adding the
following definitions thereto:

                  "Sixth Amendment" means the Sixth Amendment to this Agreement
         executed by Borrower and Bank on April 23, 1999.

         Article III of the Loan Agreement is hereby amended by adding the
following Section 3.20.

                  3.20 Conditions Precedent in Connection with the Sixth
         Amendment. The obligation of Bank to enter into the Sixth Amendment is
         subject to satisfaction of the following conditions precedent:

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                  (a) Receipt of Sixth Amendment and Compliance Certificate.
         Bank shall have received multiple counterparts of the Sixth Amendment,
         as requested by Bank, and the Compliance Certificate duly executed by
         an authorized officer for Borrower.

                  (b) Accuracy of Representations and Warranties and No Event of
         Default. The representations and warranties contained in Article IV of
         the Loan Agreement shall be true and correct in all material respects
         on the date of the Sixth Amendment with the same effect as though such
         representations and warranties had been made on such date; and no Event
         of Default shall have occurred and be continuing or will have occurred
         at the completion of the making of such Loan.

                  (c) Legal Matters Satisfactory to Special Counsel to Bank. All
         legal matters incident to the consummation of the transactions
         contemplated by the Sixth Amendment shall be satisfactory to the firm
         of Porter & Hedges, L.L.P., special counsel for Bank.

                  (d) No Material Adverse Change. No material adverse change
         shall have occurred since the date of this Agreement in the condition,
         financial or otherwise, of Borrower.

         Article V of the Loan Agreement is hereby amended by revising the
following Section 5.19, as amended pursuant to the First Amendment, in its
entirety to read as follows:

                  5.19 Tangible Net Worth Requirement. Effective December 31,
         1998, Borrower shall maintain a total Tangible Net Worth of not less
         than $38,000,000.00, increasing by: (x) fifty percent (50%) of net
         income (excluding losses) of Borrower subsequent to December 31, 1998,
         and (y) one hundred percent (100%) of any increases in shareholders'
         equity resulting from the sale or issuance of stock in Borrower
         subsequent to December 31, 1998. For purposes of this Section,
         shareholders' equity shall be deemed to include the consideration paid
         to Borrower for its sale of the 300,000 shares of 9% Series A Preferred
         Stock, par value $0.01 per share, pursuant to the ECT Transaction, as
         well as any consideration paid to Borrower for the exercise of any of
         the 1,000,000 warrants that are exercisable for the purchase of
         1,000,000 shares of common stock of Carrizo Oil & Gas, Inc., par value
         $0.01 per share, pursuant to the ECT Transaction, but shareholder's
         equity shall exclude the value of any such 9% Series A Preferred Stock
         that is subsequently redeemed by the issuance of common stock of
         Borrower.

         II. Reaffirmation of Representations and Warranties. To induce Bank to
enter into this Sixth Amendment, Borrower hereby reaffirms, as of the date
hereof, its representations and warranties contained in Article IV of the Loan
Agreement and in all other documents executed pursuant thereto, and additionally
represents and warrants as follows:

                  A. The execution and delivery of this Sixth Amendment and the
         performance by Borrower of its obligations under this Sixth Amendment
         are within Borrower's power, have been duly authorized by all necessary
         corporate action, have received all necessary governmental approval (if
         any shall be required), and do not and will not contravene or 

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         conflict with any provision of law or of the charter or by-laws of
         Borrower or of any agreement binding upon Borrower.

                  B. The Loan Agreement as amended by this Sixth Amendment,
         represents the legal, valid and binding obligations of Borrower,
         enforceable against Borrower in accordance with its terms, subject as
         to enforcement only to bankruptcy, insolvency, reorganization,
         moratorium or other similar laws affecting the enforcement of
         creditors' rights generally.

                  C. No Event of Default or Unmatured Event of Default has
         occurred and is continuing as of the date hereof.

         III. Defined Terms. Except as amended hereby, terms used herein that
are defined in the Loan Agreement shall have the same meanings in this Sixth
Amendment.

         IV. Reaffirmation of Loan Agreement. This Sixth Amendment shall be
deemed to be an amendment to the Loan Agreement, and the Loan Agreement, as
further amended hereby, is hereby ratified, approved and confirmed in each and
every respect. All references to the Loan Agreement herein and in any other
document, instrument, agreement or writing shall hereafter be deemed to refer to
the Loan Agreement as amended hereby.

         V. Entire Agreement. The Loan Agreement, as hereby further amended,
embodies the entire agreement between Borrower and Bank and supersedes all prior
proposals, agreements and understandings relating to the subject matter hereof.
Borrower certifies that it is relying on no representation, warranty, covenant
or agreement except for those set forth in the Loan Agreement as hereby further
amended and the other documents previously executed or executed of even date
herewith.

         VI. Governing Law. THIS SIXTH AMENDMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS AND THE APPLICABLE
LAWS OF THE UNITED STATES OF AMERICA. This Sixth Amendment has been entered into
in Harris County, Texas, and it shall be performable for all purposes in Harris
County, Texas. Courts within the State of Texas shall have jurisdiction over any
and all disputes between Borrower and Bank, whether in law or equity, including,
but not limited to, any and all disputes arising out of or relating to this
Sixth Amendment or any other Loan Document; and venue in any such dispute
whether in federal or state court shall be laid in Harris County, Texas.

         VII. Severability. Whenever possible each provision of this Sixth
Amendment shall be interpreted in such manner as to be effective and valid under
applicable law, but if any provision of this Sixth Amendment shall be prohibited
by or invalid under applicable law, such provision shall be ineffective to the
extent of such prohibition or invalidity, without invalidating the remainder of
such provision or the remaining provisions of this Sixth Amendment.


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         VIII Execution in Counterparts. Each party hereto acknowledges that
this Agreement may be executed in several counterparts by each party at
different times and in different locations; that each separate counterpart
bearing the signature of any party may be effectively delivered to the other
parties by the delivery of an electronic facsimile sent via telecopier; that
each party so delivering any such counterpart shall be bound by its facsimile
signature thereon; and that the signature pages from counterparts signed by each
party may be collated into one or more copies of this agreement, which shall
constitute one and the same agreement among all parties hereto.

         IX Section Captions. Section captions used in this Sixth Amendment are
for convenience of reference only, and shall not affect the construction of this
Sixth Amendment.

         X Successors and Assigns. This Sixth Amendment shall be binding upon
Borrower and Bank and their respective successors and assigns, and shall inure
to the benefit of Borrower and Bank, and the respective successors and assigns
of Bank.

         XI Non-Application of Chapter 346 of Texas Finance Codes. In no event
shall Chapter 346 of the Texas Finance Code (which regulates certain revolving
loan accounts and revolving tri-party accounts) apply to this Loan Agreement as
hereby further amended or any other Loan Documents or the transactions
contemplated hereby.

         XII Notice. THIS SIXTH AMENDMENT TOGETHER WITH THE LOAN AGREEMENT, AND
THE OTHER LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT BETWEEN THE PARTIES AND
MAY NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES. THERE ARE NO UNWRITTEN ORAL AGREEMENTS BETWEEN THE
PARTIES.

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

BANK                                        BORROWER

COMPASS BANK                                CARRIZO OIL & GAS, INC.


By:                                         By:                           
   ------------------------------              --------------------------------
      Kathleen J. Bowen                           Frank A. Wojtek
      Vice President                              Vice President


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                             COMPLIANCE CERTIFICATE


                  I, Frank A. Wojtek, Vice President of CARRIZO OIL & GAS, INC.
(the "Company"), pursuant to Section 3.20 of the First Amended, Restated, and
Combined Loan Agreement dated as of August 28, 1997, as amended, by and among
COMPASS BANK ("Bank") and the Company (the "Agreement") do hereby certify, as of
the date hereof, that to my knowledge:

         1.       No Event of Default (as defined in the Agreement) has occurred
                  and is continuing, and no Unmatured Event of Default (as
                  defined in the Agreement) has occurred and is continuing;

         2.       No material adverse change has occurred in the business
                  prospects, financial condition, or the results of operations
                  of the Company since the date of the previous Financial
                  Statements (as defined in the Agreement) provided to Bank;

         3.       Each of the representations and warranties of the Company
                  contained in Article IV of the Agreement is true and correct
                  in all respects.

                  This certificate is executed this 23 day of April 1999.


                                                ----------------------------
                                                      Frank A. Wojtek


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