SECURITIES PURCHASE AGREEMENT

Exhibit 10.1

SECURITIES PURCHASE AGREEMENT

     This Securities Purchase Agreement (this “ Agreement ”) is dated as of September 11, 2007, between Carrizo Oil & Gas, Inc., a Texas corporation (the “ Company ”), and the purchaser identified on the signature page hereto (the “ Purchaser ”).

     WHEREAS, subject to the terms and conditions set forth in this Agreement, the Company desires to issue and sell to the Purchaser, and the Purchaser desires to purchase from the Company, shares of Common Stock (as defined herein) as set forth herein on the Closing Date (as defined herein) pursuant to an effective Registration Statement on Form S-3, Commission File No. 333-142346.

     NOW, THEREFORE, IN CONSIDERATION of the mutual covenants contained in this Agreement, and for other good and valuable consideration the receipt and adequacy of which are hereby acknowledged, the Company and the Purchaser agree as follows:

ARTICLE I.
DEFINITIONS

     1.1 Definitions . In addition to the terms defined elsewhere in this Agreement, for all purposes of this Agreement, the following terms have the meanings indicated in this Section 1.1:

     “ Action ” means any action, suit, inquiry, notice of violation, proceeding (including any partial proceeding such as a deposition) or investigation pending or threatened in writing against or affecting the Company, any Subsidiary or any of their respective properties before or by any court, arbitrator, governmental or administrative agency, regulatory authority (federal, state, county, local or foreign), stock market, stock exchange or trading facility.

     “ Affiliate ” means any Person that, directly or indirectly through one or more intermediaries, controls or is controlled by or is under common control with a Person, as such terms are used in and construed under Rule 144. With respect to a Purchaser, any investment fund or managed account that is managed on a discretionary basis by the same investment manager as such Purchaser will be deemed to be an Affiliate of such Purchaser.

     “ Business Day ” means any day except Saturday, Sunday and any day that is a federal legal holiday or a day on which banking institutions in the State of New York are authorized or required by law or other governmental action to close.

     “ Closing ” means the closing of the purchase and sale of the Shares pursuant to Section 2.1.

     “ Closing Date ” means the third (3 ^rd ) Trading Day following the date of this Agreement.

     “ Commission ” means the United States Securities and Exchange Commission.

     “ Common Stock ” means the common stock of the Company, par value $.01 per share, and any securities into which such common stock may hereafter be reclassified.

     “ Common Stock Equivalents ” means any securities of the Company which would entitle the holder thereof to acquire at any time Common Stock, including, without limitation, any debt, preferred stock, rights, options, warrants or other instrument that is at any time convertible into or exercisable or exchangeable for, or otherwise entitles the holder thereof to receive, Common Stock.

     “ Company Counsel ” means Baker Botts L.L.P.

     “ Disclosure Documents ” means the Registration Statement, the SEC Reports and the Schedules, considered together.

     “ Exchange Act ” means the Securities Exchange Act of 1934, as amended.

     “ GAAP ” shall have the meaning ascribed to such term in Section 3.1(f).

     “ Lien ” means a lien, charge, security interest, encumbrance, right of first refusal, preemptive right or other restriction.

     “ Material Adverse Effect ” means any of (a) a material and adverse effect on the legality, validity or enforceability of any Transaction Document, (b) a material and adverse effect on the results of operations, assets, business or condition (financial or otherwise) of the Company and the Subsidiaries, taken as a whole, or (c) a material and adverse impairment to the Company’s ability to perform, on a timely basis, its obligations under any Transaction Document.

     “ Material Permits ” means all certificates, authorizations and permits issued by the appropriate federal, state, local or foreign regulatory authorities necessary for the Company and its Subsidiaries to conduct their respective businesses as described in the Disclosure Documents.

     “ Per Share Purchase Price ” equals $41.40, subject to adjustment for reverse and forward stock splits, stock dividends, stock combinations and other similar transactions of the Common Stock that occur after the date of this Agreement and prior to the Closing.

     “ Person ” means an individual or corporation, partnership, trust, incorporated or unincorporated association, joint venture, limited liability company, joint stock company, government (or an agency or subdivision thereof) or other entity of any kind.

     “ Prospectus Supplement ” means the supplement to the base prospectus contained in the Registration Statement and filed or to be filed with the Commission pursuant to Rule 424(b) promulgated under the Securities Act.

     “ RBC ” means RBC Capital Markets Corporation.

     “ Registration Statement ” means the registration statement on Form S-3 of the Company, (Commission File No. 333-142346) covering the sale by the Company to the Purchaser of the Shares, including the Prospectus Supplement, amendments and supplements to such registration statements or Prospectus Supplement, including pre- and post-effective amendments, all exhibits thereto, and all material incorporated by reference or deemed to be incorporated by reference in such registration statements.

     “ Regulation S-X ” means Regulation S-X promulgated by the Commission pursuant to the Exchange Act.

     “ Required Approvals ” means (i) filings required pursuant to Section 4.1 and Section 4.4, (ii) filings required in connection with the issuance and listing on The Nasdaq Global Select Market of the Shares, (iii) such filings as are required to be made under applicable state securities laws and (iv) those that have been obtained prior to the date of this Agreement.

     “ Rule 144 ” means Rule 144 promulgated by the Commission pursuant to the Securities Act, as such rule may be amended from time to time, or any similar rule or regulation hereafter adopted by the Commission having substantially the same effect as such rule.

     “ Schedules ” means the disclosure schedules prepared by the Company and attached to this Agreement.

     “ SEC Reports ” shall have the meaning ascribed to such term in Section 3.1(f).

     “ Securities Act ” means the Securities Act of 1933, as amended.

     “ Shares ” means the shares of Common Stock issued or issuable to the Purchaser pursuant to this Agreement.

     “ Short Sale ” means all “short sales” as defined in Rule 200 of Regulation SHO promulgated under the Exchange Act.

     “ Subscription Amount ” means, as to the Purchaser, the amount set forth below the Purchaser’s signature block on the signature page hereto, in United States dollars and in immediately available funds.

     “ Subsidiary ” means any “significant subsidiary” as defined in Rule 1-02(w) of Regulation S-X promulgated by the Commission under the Exchange Act.

     “ Trading Day ” means (i) a day on which the Common Stock is traded on a Trading Market (other than the OTC Bulletin Board), or (ii) if the Common Stock is not listed on a Trading Market (other than the OTC Bulletin Board), a day on which the Common Stock is traded in the over-the-counter market, as reported by the OTC Bulletin Board, or (iii) if the Common Stock is not quoted on the OTC Bulletin Board, a day on which the Common Stock is quoted in the over-the-counter market as reported by the National Quotation Bureau Incorporated (or any similar organization or agency

succeeding to its functions of reporting prices); provided that in the event that the Common Stock is not listed or quoted as set forth in (i), (ii) and (iii) hereof, then Trading Day shall mean a Business Day.

     “ Trading Market ” means whichever of the New York Stock Exchange, the American Stock Exchange, The NASDAQ Stock Market or the OTC Bulletin Board on which the Common Stock is listed or quoted for trading on the date in question.

     “ Transaction Documents ” means this Agreement and any other agreements executed or delivered by the Company in connection with the transactions contemplated hereunder.

     “ Transfer Agent ” means American Stock Transfer & Trust Company.

ARTICLE II.
PURCHASE AND SALE

     2.1 Closing . On the Closing Date, the Purchaser shall purchase from the Company and the Company shall issue and sell to the Purchaser, a number of Shares equal to the Purchaser’s Subscription Amount divided by the Per Share Purchase Price. Upon satisfaction of the conditions set forth in Section 2.3, the Closing shall occur telephonically or at such location as the parties shall mutually agree.

     2.2 Deliveries .

     (a) On the Closing Date, the Company shall:

     (i) deliver or cause to be delivered the number of Shares equal to the Purchaser’s Subscription Amount divided by the Per Share Purchase Price, by electronic book-entry at The Depository Trust Company (“DTC”), registered in the Purchaser’s name and address as set forth on the Purchaser’s signature page hereto, and released by the Transfer Agent, to the Purchaser at the Closing. No later than one (1) Business Day after the execution of this Agreement by the Purchaser and the Company, the Purchaser shall: (I) direct the broker-dealer at which the account or accounts to be credited with the Shares are maintained, which broker-dealer shall be a DTC participant, to set up a Deposit/Withdrawal at Custodian (“DWAC”) instructing the Transfer Agent to credit such account or accounts with the Shares by means of an electronic book entry delivery, and (II) remit by wire transfer the amount of funds equal to the aggregate purchase price for the Shares being purchased by the Purchaser to the following account:

Carrizo Oil & Gas, Inc.
                                         

ABA#                            

Acct#                          ; or

It is the Purchaser’s responsibility to (A) make the necessary wire transfer in a timely manner and (B) arrange for settlement by way of DWAC in a timely

manner. If the Purchaser does not deliver the aggregate purchase price for the Shares or does not make proper arrangements for settlement in a timely manner, the Shares may not be delivered at Closing to the Purchaser or the Purchaser may be excluded from the Closing altogether;

     (ii) deliver or cause to be delivered to the Purchaser any prospectus and Prospectus Supplement as required under the Securities Act; and

     (iii) deliver or cause to be delivered to the Purchaser a legal opinion of Company Counsel, in the form of Exhibit A attached hereto, addressed to the Purchaser and providing that RBC and the Purchaser are entitled to rely thereon. Without limiting the generality of Section 2.3(b), the Purchaser’s obligation to fund on the Closing Date shall be conditioned upon satisfaction of the conditions in Section 2.3(b), including delivery of any receivables by the Company.

     (b) On the Closing Date, the Purchaser shall deliver or cause to be delivered to the Company the Purchaser’s Subscription Amount by remitting by wire transfer the amount of funds equal to the aggregate purchase price for the Shares being purchased by the Purchaser to an account designated by the Company.

     2.3 Closing Conditions .

     (a) The obligations of the Company hereunder in connection with the Closing are subject to the following conditions being met:

     (i) all representations and warranties of the Purchaser contained herein were true and correct on the date hereof and remain true and correct as of the Closing Date, except that those representations and warranties that address matters only as of a particular date shall remain true and correct as of such date;

     (ii) all obligations, covenants and agreements of the Purchaser required to be performed at or prior to the Closing Date shall have been performed;

     (iii) the Purchaser shall have delivered the Subscription Amount in accordance with Section 2.2(b) of this Agreement; and

     (iv) the transactions contemplated in each of those other Securities Purchase Agreements between the Company and the purchasers named therein, each dated the date hereof and each containing terms and conditions substantially similar to the terms and conditions hereof, shall be consummated prior to, simultaneous with or immediately following the transactions contemplated hereby.

     (b) The obligations of the Purchaser hereunder in connection with the Closing are subject to the following conditions being met or waived in writing by the Purchaser:

     (i) all representations and warranties of the Company contained herein were true and correct on the date hereof and remain true and correct as of the Closing Date, except that those representations and warranties that address matters only as of a particular date shall remain true and correct as of such date;

     (ii) all obligations, covenants and agreements of the Company required to be performed at or prior to the Closing Date shall have been performed;

     (iii) the Company shall have delivered the items set forth in Section 2.2(a) of this Agreement;

     (iv) there shall have been no Material Adverse Effect with respect to the Company since the date hereof;

     (v) the Prospectus Supplement shall have been filed with the Commission and the Registration Statement shall be effective and available for the issuance and sale of the Shares hereunder;

     (vi) RBC shall have received signed letters from Pannell Kerr Forster of Texas, P.C. (“PKF”) addressed to RBC and the Board of Directors of the Company confirming that they are an independent registered public accounting firm within the meaning of the Securities Act and the rules and regulations promulgated thereunder (the “Rules”) and containing such other statements and information as is ordinarily included in accountants’ “comfort letters” with respect to the financial statements and certain financial and statistical information contained in the Registration Statement and the Prospectus Supplement;

     (vii) no order preventing or suspending the use of any prospectus or the Prospectus Supplement shall have been or shall be in effect and no order suspending the effectiveness of the Registration Statement shall be in effect and no proceedings for such purpose shall be pending before or threatened by the Commission, and any requests for additional information on the part of the Commission (to be included in the Registration Statement or the prospectus or the Prospectus Supplement or otherwise) shall have been complied with to the satisfaction of the Commission and the Purchaser; and

     (viii) from the date hereof to the Closing Date, trading in the Common Stock shall not have been suspended by the Commission and, at any time prior to the Closing Date, trading in securities generally as reported by Bloomberg Financial Markets shall not have been suspended or limited, or minimum prices shall not have been established on securities whose trades are reported by such service, nor shall a banking moratorium have been declared either by the United States or New York state authorities nor shall there have occurred any material outbreak or escalation of hostilities involving the United States of America which, in each case, in the reasonable judgment of the Purchaser, makes it impracticable to purchase the Shares at the Closing.

ARTICLE III.
REPRESENTATIONS AND WARRANTIES

     3.1 Representations and Warranties of the Company . The Company represents and warrants to each Purchaser, except as disclosed or incorporated by reference in the Registration Statement, as follows:

     (a) Organization and Qualification . The Company and each Subsidiary is an entity duly incorporated or otherwise organized, validly existing and in good standing under the laws of the jurisdiction of its incorporation or organization (as applicable), with the requisite power and authority to own and use its properties and assets and to carry on its business as currently conducted. Neither the Company nor any Subsidiary is in violation of any of the provisions of its respective certificate or articles of incorporation, bylaws or other organizational, charter or equivalent documents. The Company and each Subsidiary is duly qualified to conduct business and is in good standing as a foreign corporation or other entity in each jurisdiction in which the nature of the business conducted or property owned by it makes such qualification necessary, except where the failure to be so qualified or in good standing, as the case may be, could not, individually or in the aggregate, have or reasonably be expected to have a Material Adverse Effect.

     (b) Authorization; Enforcement . The Company has the requisite corporate power and authority to enter into and to consummate the transactions contemplated by each of the Transaction Documents and otherwise to carry out its obligations hereunder and thereunder. The execution and delivery of each of the Transaction Documents by the Company and the consummation by it of the transactions contemplated hereby and thereby have been duly authorized by all necessary action on the part of the Company and no further action is required by the Company, its board of directors or shareholders in connection herewith and therewith other than in connection with the Required Approvals. Each Transaction Document has been (or upon delivery will have been) duly executed by the Company and, when delivered in accordance with the terms hereof, will constitute the valid and binding obligation of the Company, enforceable against the Company in accordance with its terms, except (i) as limited by applicable bankruptcy, insolvency, reorganization, moratorium and other laws of general application affecting enforcement of creditors’ rights generally and (ii) as limited by laws relating to the availability of specific performance, injunctive relief or other equitable remedies.

     (c) No Conflicts . The execution, delivery and performance of the Transaction Documents by the Company and the consummation by the Company of the transactions contemplated thereby do not and will not (i) conflict with or violate any provision of the Company’s or any Subsidiary’s certificate or articles of incorporation, bylaws or other organizational, charter or equivalent documents, or (ii) conflict with, or constitute a default (or an event that with notice or lapse of time or both would become a default) under, or give to others any rights of termination, amendment, acceleration or cancellation (with or without notice, lapse of time or both) of, any agreement, credit facility, debt or instrument (evidencing a Company or Subsidiary debt or otherwise) or other understanding to which the Company or any Subsidiary is a party or by which any property or asset of the Company or any Subsidiary is bound or affected, or (iii) subject

to the Required Approvals, result in a violation of any law, rule, regulation, order, judgment, injunction, decree or other restriction of any court or governmental authority to which the Company or a Subsidiary is subject (including federal and state securities laws and regulations and the rules and regulations of any self-regulatory organization to which the Company or its securities are subject), or by which any property or asset of the Company or a Subsidiary is bound or affected; except in the case of each of clauses (ii) and (iii), such as would not, individually or in the aggregate, have or reasonably be expected to result in a Material Adverse Effect.

     (d) Issuance of the Shares; Reservation of Common Stock . The Shares have been duly authorized and, when issued and paid for in accordance with this Agreement, will be duly and validly issued, fully paid and nonassessable. The Company has reserved from its duly authorized capital stock the maximum number of shares of Common Stock issuable pursuant to this Agreement. The issuance by the Company of the Shares has been registered under the Securities Act. The Registration Statement is effective and available for the issuance, offering and sale of the Shares and the Company has not received any notice that the Commission has issued or intends to issue a stop-order with respect to the Registration Statement or that the Commission otherwise has suspended or withdrawn the effectiveness of the Registration Statement, either temporarily or permanently, or intends or has threatened in writing to do so. The “Plan of Distribution” section under the Registration Statement permits the issuance and sale of the Shares hereunder. Except as described in Section 4.6, and except to the extent the Purchaser is an affiliate of the Company, and assuming the accuracy of the representations and warranties of the Purchaser herein, the Shares at the time of delivery will be freely transferable and tradeable by the Purchaser without restriction created by the Company. The Company has filed all applications and other documents necessary for the Shares to be listed on The Nasdaq Global Select Market, subject only to official notice of issuance.

     (e) Capitalization . The number of shares and type of all authorized, issued and outstanding capital stock of the Company, and all shares of Common Stock reserved for issuance under the Company’s various option and incentive plans, is set forth in the SEC Reports. All outstanding shares of capital stock are duly authorized, validly issued, fully paid and nonassessable and have been issued in compliance with all applicable securities laws. Except as set forth in the SEC Reports, no securities of the Company are entitled to preemptive or similar rights, and no Person has any right of first refusal, preemptive right, right of participation, or any similar right to participate in the transactions contemplated by the Transaction Documents. Except as a result of the purchase and sale of the Shares or except as disclosed in the SEC Reports, there are no outstanding options, warrants, scrip rights to subscribe to, calls or commitments of any character whatsoever relating to, Common Stock Equivalents, or contracts, commitments, understandings or arrangements by which the Company or any Subsidiary is or may become bound to issue additional shares of Common Stock, or Common Stock Equivalents. There are no anti-dilution or price adjustment provisions contained in any outstanding security issued by the Company (or in any agreement providing rights to security holders) other than under the Company’s incentive plan. The issue and sale of the Shares will not, immediately or with the passage of time, obligate the Company to issue shares of Common Stock or other securities to any Person (other than the

Purchaser) and will not result in a right of any holder of Company securities to adjust the exercise, conversion, exchange or reset price under such securities.

     (f) SEC Reports; Financial Statements . The Company has furnished or made available to the Purchaser true, correct and complete copies of all reports required to be filed by it under the Exchange Act, including pursuant to Section 13(a) or 15(d) thereof, for all periods subsequent to December 3