W. R. BERKLEY CORPORATION 7.375% Senior Notes Due 2019 UNDERWRITING AGREEMENT

Exhibit 1.1

$300,000,000

W. R. BERKLEY CORPORATION

7.375% Senior Notes Due 2019

UNDERWRITING AGREEMENT

September 9, 2009

September 9, 2009

Credit Suisse Securities (USA) LLC
           As Representatives of the Several Underwriters

Dear Sirs and Mesdames:

          W. R. Berkley Corporation, a Delaware corporation (the “ Company ”), proposes to issue and sell to the several Underwriters named in Schedule I hereto (the “ Underwriters ”) $300,000,000 principal amount of its 7.375% Senior Notes due 2019 (the “ Securities ”) to be issued pursuant to the provisions of an Indenture, dated as of February 14, 2003, as supplemented by the Sixth Supplemental Indenture, to be dated as of September 14, 2009 (the “ Indenture ”), between the Company and The Bank of New York Mellon, as Trustee (the “ Trustee ”).

          The Company has filed with the Securities and Exchange Commission (the “ Commission ”) a registration statement, including a prospectus, on Form S-3 (No. 333-155724) covering the registration of the securities of the Company, including the Securities, under the Securities Act of 1933, as amended (the “ Securities Act ”), and the offering thereof from time to time in accordance with Rule 415 of the rules and regulations of the Commission under the Securities Act (the “ Rules and Regulations ”) and the Company has filed such post-effective amendments thereto as may be required prior to the execution of this Agreement. Promptly after execution and delivery of this Agreement, the Company will prepare and file a final prospectus and final prospectus supplement in accordance with the provisions of paragraph (b) of Rule 424 of the Rules and Regulations. “ Registration Statement” at any particular time means such registration statement in the form then filed with the Commission, including any amendment thereto, any document incorporated by reference therein and any information in a prospectus or prospectus supplement deemed or retroactively deemed to be a part thereof pursuant to Rule 430B or 430C of the Rules and Regulations, that in any case has not been superseded or modified. “ Registration Statement ” without reference to a time means the Registration Statement as of the time of the first contract of sale for the Securities, which time shall be considered the “ effective date ” of such Registration Statement relating to the Securities. For purposes of this definition, information contained in a form of prospectus or prospectus supplement that is deemed or retroactively deemed to be a part of the Registration Statement pursuant to Rule 430B of the Rules and Regulations shall be considered to be included in the Registration Statement as of the time specified in Rule 430B of the Rules and Regulations. “ Statutory Prospectus ” as of any particular time means the prospectus relating to the Securities that is included in the Registration Statement immediately prior to that time, including all information contained in a form of prospectus or prospectus supplement deemed to be a part

thereof pursuant to Rule 430B or 430C of the Rules and Regulations that in any case has not been superseded or modified. For purposes of this definition, information contained in a form of prospectus (including a prospectus supplement) that is deemed or retroactively deemed to be a part of the Registration Statement pursuant to Rule 430B of the Rules and Regulations shall be considered to be included in the Statutory Prospectus only as of the actual time that form of prospectus (including a prospectus supplement) is filed with the Commission pursuant to Rule 424(b) of the Rules and Regulations and not retroactively. “ Prospectus ” means the Statutory Prospectus that discloses the public offering price and other final terms of the Securities and otherwise satisfies Section 10(a) of the Securities Act and the term “ preliminary prospectus ” means the Statutory Prospectus, as supplemented by the Preliminary Prospectus Supplement, dated September 9, 2009.

          For purposes of this Agreement, “ Issuer Free Writing Prospectus ” means any “issuer free writing prospectus,” as defined in Rule 433(h) of the Rules and Regulations, relating to the Securities in the form filed or required to be filed with the Commission or, if not required to be filed, in the form retained or required to be retained in the Company’s records pursuant to Rule 433(g) of the Rules and Regulations, “ General Use Issuer Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is intended for general distribution to prospective investors, as evidenced by its being specified in Schedule II hereto and “ Limited Use Issuer Free Writing Prospectus ” means any Issuer Free Writing Prospectus that is not a General Use Issuer Free Writing Prospectus. All references to the terms “Registration Statement,” “Prospectus” and “preliminary prospectus” shall be deemed to include all documents incorporated therein by reference pursuant to the Securities Exchange Act of 1934, as amended (the “ Exchange Act ”). For purposes of this Agreement, all references to the Registration Statement, Prospectus or any preliminary prospectus or to any amendment or supplement to any of them shall be deemed to include any copy filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval System.

          1. Representations and Warranties . The Company represents and warrants to and agrees with each of the Underwriters that:

     (a) The Registration Statement has become effective; no stop order suspending the effectiveness of the Registration Statement is in effect, and no proceedings for such purpose are pending before or, to the knowledge of the Company, threatened by the Commission.

     (b) (i) (A) At the time the Registration Statement initially became effective, (B) at the time of each amendment thereto for the purposes of complying with Section 10(a)(3) of the Securities Act (whether by post-effective amendment, incorporated report or form of prospectus), (C) at the effective time of the Registration Statement relating to the Securities and (D) on the Closing Date, the Registration Statement conformed and will confirm in all material respects to the requirements of the Securities Act and the Rules and Regulations and did not include any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary to make the statements therein not misleading, (ii) (A) on its date, (B) at the time of filing the Prospectus pursuant to Rule 424(b) of the Rules and Regulations and (C) on the Closing Date, the Prospectus will conform in all material respects to the requirements of the Securities Act

and the Rules and Regulations, (iii) as of 5:30 p.m. New York City time on the date of this Agreement (the “ Applicable Time ”), neither the General Use Issuer Free Writing Prospectus issued at or prior to the Applicable Time and the Statutory Prospectus identified in Schedule II attached hereto and all other documents set forth on Schedule II, all considered together (collectively, the “ General Disclosure Package ”), nor any individual Limited Use Issuer Free Writing Prospectus, when considered together with the General Disclosure Package, included any untrue statement of a material fact or omitted to state any material fact necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, except that the foregoing does not apply to (A) statements in or omissions from any prospectus included in the Registration Statement or any Issuer Free Writing Prospectus in reliance upon or in conformity with written information furnished to the Company by any Underwriter through the representative or representatives of the Underwriter (the “ Representatives ”) specifically for use therein, (iv) (A) on its date, (B) at the time of its filing pursuant to Rule 424(b) of the Rules and Regulations and (C) on the Closing Date, the Prospectus does not include and will not include any untrue statement of a material fact or omit to state any material fact required to be stated therein, in light of the circumstances under which they were made, or necessary to make the statements therein not misleading, except that the foregoing does not apply to (A) statements in or omissions from any of such documents based upon written information furnished to the Company by any Underwriter through the Representatives specifically for use therein or (B) that part of the Registration Statement that constitutes the Statement of Eligibility (Form T-1) under the Trust Indenture Act of 1939, as amended (the “ Trust Indenture Act ”), of the Trustee; and (v) the documents incorporated by reference in the Prospectus, at the time they were, or hereafter, are filed with the Commission, complied and, at any time when a prospectus relating to the Securities is required (or would be required, but for the provisions of Rule 172 of the Rules and Regulations) to be delivered under the Securities Act in connection with sales by any Underwriter or dealer, will comply as to form in all material respects with the requirements of the Exchange Act and the rules and regulations thereunder.

     (c) At the earliest time after the filing of the Registration Statement that the Company or another offering participant made a bona fide offer (within the meaning of Rule 164(h)(2) of the Rules and Regulations) of the Securities and at the date of this Agreement, the Company was not and is not an “ineligible issuer” as defined in Rule 405 of the Rules and Regulations.

     (d) Each Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offer and sale of the Securities or until any earlier date that the Company notified or notifies the Representatives as described in the next sentence, did not, does not and will not include any information that conflicted, conflicts or will conflict with the information then contained in the Registration Statement. If at any time following issuance of an Issuer Free Writing Prospectus there occurred or occurs an event or development as a result of which such Issuer Free Writing Prospectus conflicted or would conflict with the information then contained in the Registration Statement or as result of which such Issuer Free Writing Prospectus, if republished immediately following such event or development, would include an untrue statement of a material fact or would omit to state a material fact

necessary in order to make the statements therein, in light of the circumstances under which they were made, not misleading, (A) the Company has promptly notified or will promptly notify the Representatives and (B) the Company has promptly amended or will promptly amend or supplement such Issuer Free Writing Prospectus to eliminate or correct such conflict, untrue statement or omission.

     (e) The Company has been duly incorporated and is an existing corporation in good standing under the laws of the State of Delaware, with power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package and the Prospectus; and the Company is duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except in such jurisdictions where the failure to be so qualified would not individually or in the aggregate have a material adverse effect on the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries taken as a whole (“ Material Adverse Effect ”).

     (f) Each Significant Subsidiary (as defined below) of the Company has been duly incorporated and is an existing corporation in good standing under the laws of the jurisdiction of its incorporation, with power and authority (corporate and other) to own its properties and conduct its business as described in the General Disclosure Package and the Prospectus; and each Significant Subsidiary of the Company is, to the extent applicable, duly qualified to do business as a foreign corporation in good standing in all other jurisdictions in which its ownership or lease of property or the conduct of its business requires such qualification, except where the failure to be so qualified would not individually or in the aggregate have a Material Adverse Effect; all of the issued and outstanding capital stock of each Significant Subsidiary of the Company has been duly authorized and validly issued and is fully paid and nonassessable; and the capital stock of each Significant Subsidiary owned by the Company, directly or through subsidiaries, is owned free from liens, encumbrances and defects. As used herein, “ Significant Subsidiaries ” means Admiral Insurance Company, Berkley Regional Insurance Company, Berkley Insurance Company and Nautilus Insurance Company, which are currently the only operating insurance companies that are “significant subsidiaries” of the Company as that term is defined in Rule 1-02(w) of Regulation S-X of the Rules and Regulations.

     (g) The Indenture has been duly qualified under the Trust Indenture Act and has been duly authorized, and on the Closing Date (as defined below) will be duly executed and delivered by the Company and a valid and binding agreement of the Company, enforceable in accordance with its terms except as (i) the enforceability thereof may be limited by bankruptcy, insolvency or similar laws affecting creditors’ rights generally and (ii) rights of acceleration and the availability of equitable remedies may be limited by equitable principles of general applicability.

     (h) The Securities have been duly authorized and, when executed and authenticated in accordance with the provisions of the Indenture and delivered to and paid for by the Underwriters in accordance with the terms of this Agreement on the

Closing Date, such Securities will be duly executed, authenticated, issued and delivered and entitled to the benefits of the Indenture and will be valid and binding obligations of the Company, enforceable in accordance with their terms except as (i) the enforceability thereof may be limited by bankruptcy, insolvency or similar laws affecting creditors’ rights generally and (ii) rights of acceleration and the availability of equitable remedies may be limited by equitable principles of general applicability; and the Securities and the Indenture will conform to the information in the General Disclosure Package and will conform to the descriptions thereof in the Prospectus.

     (i) Except as disclosed in the General Disclosure Package and the Prospectus, there are no contracts, agreements or understandings between the Company and any person that would give rise to a valid claim against the Company or any Underwriter for a brokerage commission, finder’s fee or other like payment in connection with this offering.

     (j) There are no contracts, agreements or understandings between the Company and any person granting such person the right to require the Company to file a registration statement under the Securities Act with respect to any securities of the Company owned or to be owned by such person or to require the Company to include such securities in the securities registered pursuant to the Registration Statement or in any securities being registered pursuant to any other registration statement filed by the Company under the Securities Act.

     (k) No consent, approval, authorization, or order of, or filing with, any governmental agency or body or any court is required for the performance by the Company of its obligations under this Agreement, the Indenture or the Securities, except such as have been obtained and made under the Securities Act, as contemplated under Section 5(a) hereof, and such as may be required under state securities laws.

     (l) The execution and delivery of, and the performance by the Company of its obligations under, this Agreement, the Indenture and the Securities will not result in a breach or violation of any of the terms and provisions of, or constitute a default under, any statute, any rule, regulation or order of any governmental agency or body or any court, domestic or foreign, having jurisdiction over the Company or any Significant Subsidiaries of the Company or any of their material properties, or any material agreement or instrument to which the Company or any such subsidiary is a party or by which the Company or any such subsidiary is bound or to which any of the properties of the Company or any such subsidiary is subject, or the charter or by-laws of the Company or any such subsidiary, and the Company has full power and authority to authorize, issue and sell the Securities as contemplated by this Agreement.

     (m) This Agreement has been duly authorized, executed and delivered by the Company.

     (n) Except as disclosed in the General Disclosure Package and the Prospectus, the Company and its Significant Subsidiaries have good and marketable title to all real properties and all other properties and assets owned by them, in each case free from liens,

encumbrances and defects that would affect the value thereof or interfere with the use made or to be made thereof by them, other than liens, encumbrances and defects that would not individually or in the aggregate have a Material Adverse Effect; and except as disclosed in the General Disclosure Package and the Prospectus, the Company and its subsidiaries hold any leased real or personal property under valid and enforceable leases with no exceptions that would individually or in the aggregate have a Material Adverse Effect.

     (o) The Company and its Significant Subsidiaries possess adequate certificates, authorities or permits issued by appropriate governmental agencies or bodies necessary to conduct the business now operated by them and have not received any notice of proceedings relating to the revocation or modification of any such certificate, authority or permit that, if determined adversely to the Company or any of its Significant Subsidiaries, would individually or in the aggregate have a Material Adverse Effect.

     (p) The Company has made all required filings under applicable insurance holding company statutes, and has received approvals of acquisition of control and/or affiliate transactions, in each jurisdiction in which such filings or approvals are required, except where the failure to have made such filings or receive such approvals in any such jurisdiction would not have individually or in the aggregate a Material Adverse Effect; each of the Company’s Significant Subsidiaries that is required to be organized and licensed as an insurance or reinsurance company (the “ Insurance Subsidiaries ”) in its jurisdiction of incorporation is duly organized and licensed as an insurance or reinsurance company in its respective jurisdiction of incorporation, and each such Significant Subsidiary is duly licensed or authorized as an insurer or reinsurer (the “ Insurance Licenses ”) in each other jurisdiction in which such licensing or authorization is required, except where the failure to be so licensed or authorized in any such jurisdiction would not have individually or in the aggregate a Material Adverse Effect; there is no pending or, to the knowledge of the Company, threatened action, suit, proceeding or investigation that would reasonably be expected to lead to the revocation, termination or suspension of any such Insurance Licenses, the revocation, termination or suspension of which would have individually or in the aggregate a Material Adverse Effect; and except as disclosed in the General Disclosure Package and the Prospectus, no insurance regulatory agency or body has issued any order or decree impairing, restricting or prohibiting the payment of dividends of any Company subsidiary to its respective parent which would have individually or in the aggregate a Material Adverse Effect.

     (q) The Company and each of its Significant Subsidiaries is in compliance with the requirements of all laws, ordinances, governmental rules or regulations or court decrees to which it may be subject, and has filed all notices, reports, documents or other information required to be filed thereunder, except where the failure to so comply or file would not individually or in the aggregate have a Material Adverse Effect.

     (r) Except as disclosed in the General Disclosure Package and the Prospectus, neither the Company nor any of its Insurance Subsidiaries is in violation of, or in default in the performance, observance or fulfillment of, any obligation, agreement, covenant or condition contained in reinsurance treaties, contracts, agreements and arrangements to

which the Company or any of its Insurance Subsidiaries is a party, except for such violations or defaults which would not individually or in the aggregate have a Material Adverse Effect; neither the Company nor any of its Insurance Subsidiaries has received any notice from any of the other parties to such treaties, contracts, agreements or arrangements that such other party intends not to perform its obligations thereunder and none of them has any reason to believe that any of the other parties to such treaties, contracts, agreements or arrangements will be unable to perform its obligations thereunder, except to the extent that such nonperformance would not individually or in the aggregate have a Material Adverse Effect.

     (s) To the knowledge of the Company and its Insurance Subsidiaries, no change in any insurance law or regulation is pending that would reasonably be expected to have individually or in the aggregate a Material Adverse Effect, except as described in the General Disclosure Package and the Prospectus.

     (t) No labor dispute with the employees of the Company or any Significant Subsidiary exists or, to the knowledge of the Company, is imminent that would reasonably be expected to have individually or in the aggregate a Material Adverse Effect.

     (u) The Company and its subsidiaries own, possess or can acquire on reasonable terms, adequate trademarks, trade names and other rights to inventions, know-how, patents, copyrights, confidential information and other intellectual property (collectively, “ intellectual property rights ”) materially necessary to conduct the business now operated by them and have not received any notice of infringement of or conflict with asserted rights of others with respect to any intellectual property rights that, if determined adversely to the Company or any of its subsidiaries, would individually or in the aggregate have a Material Adverse Effect.

     (v) Except as disclosed in the General Disclosure Package and the Prospectus, neither the Company nor any of its subsidiaries is in violation of any statute, any rule, regulation, decision or order of any governmental agency or body or any court, domestic or foreign, relating to the use, disposal or release of hazardous or toxic substances or relating to the protection or restoration of the environment or human exposure to hazardous or toxic substances (collectively, “ environmental laws ”), owns or operates any real property contaminated with any substance that is subject to any environmental laws, is liable for any off-site disposal or contamination pursuant to any environmental laws, or is subject to any claim relating to any environmental laws, which violation, contamination, liability or claim would individually or in the aggregate have a Material Adverse Effect; and the Company is not aware of any pending investigation which would reasonably be expected to lead to such a claim.

     (w) Except as disclosed in the General Disclosure Package and the Prospectus, there are no pending actions, suits or proceedings against or affecting the Company, any of its subsidiaries or any of their respective properties that would individually or in the aggregate have a Material Adverse Effect, or would materially and adversely affect the ability of the Company to perform its obligations under this Agreement; and no such

actions, suits or proceedings are, to the Company’s knowledge, threatened or contemplated.

     (x) KPMG LLP, who have certified the financial statements and supporting schedules of the Company and its subsidiaries contained in the General Disclosure Package and the Prospectus, are independent public accountants within the meaning of the Securities Act and the Rules and Regulations; except as disclosed in the General Disclosure Package and the Prospectus, the financial statements included or incorporated by reference in the Registration Statement and the General Disclosure Package and the Prospectus present fairly the financial position of the Company and its consolidated subsidiaries as of the dates shown and their results of operations and cash flows for the periods shown; except as disclosed in the General Disclosure Package and the Prospectus, such financial statements have been prepared in conformity with the generally accepted accounting principles in the United States applied on a consistent basis; except as disclosed in the General Disclosure Package and the Prospectus, the schedules included or incorporated in the Registration Statement present fairly the information required to be stated therein; and except as disclosed in the General Disclosure Package and the Prospectus, the Company and its Insurance Subsidiaries have made no material change in their insurance reserving practices since the most recent audited financial statements included in the General Disclosure Package and the Prospectus.

     (y) The statutory annual and quarterly statements of the Insurance Subsidiaries required to file such statutory statements and the statutory balance sheets and income statements included in such statutory annual and quarterly statements, most recently filed in each jurisdiction, have been prepared in conformity with required or permitted or prescribed statutory accounting principles or practices applied on a consistent basis, except as may otherwise be indicated in the notes thereto, and present fairly the financial position of the Insurance Subsidiaries (on a statutory basis) for the period covered thereby.

     (z) The Company and its subsidiaries maintain a system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with United States generally accepted accounting principles and to maintain asset accountability; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

     (aa) Except as disclosed in the General Disclosure Package and the Prospectus and except for regular dividends declared or paid consistent with past practice, since the date of the latest audited financial statements included in the General Disclosure Package and the Prospectus, (i) there has been no material adverse change, nor any development or event involving a prospective material adverse change, in the condition (financial or other), business, properties or results of operations of the Company and its subsidiaries

taken as a whole, (ii) there have not been any transactions entered into by the Company or any of its subsidiaries other than in the ordinary course of business which are material to the Company and its subsidiaries taken as a whole, and, (iii) there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of its capital stock.

     (bb) The Company is not and, after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the General Disclosure Package and the Prospectus, will not be an “investment company” as defined in the Investment Company Act of 1940.

          2. Agreements to Sell and Purchase . The Company hereby agrees to sell to the several Underwriters, and each Underwriter, upon the basis of the representations and warranties herein contained, but subject to the conditions hereinafter stated, agrees, severally and not jointly, to purchase from the Company the respective principal amount of Securities set forth in Schedule I hereto opposite its name at 99.35% of their principal amount (the “ Purchase Price ”) plus accrued interest, if any, from September 14, 2009 to the date of payment and delivery.

          3. Terms of Public Offering. The Company is advised by you that the Underwriters propose to make a public offering of their respective portions of the Securities as soon after the Registration Statement and this Agreement have become effective as in your judgment is advisable. The Company is further advised by you that the Securities are to be offered to the public initially at 100.00% of their principal amount (the “ Public Offering Price ”) plus accrued interest, if any, from September 14, 2009 to the date of payment and delivery and to certain dealers selected by you at a price that represents a concession not in excess of 0.40% of their principal amount under the Public Offering Price, and that any Underwriter may allow, and such dealers may reallow, a concession to certain other dealers not to exceed 0.25% of the principal amount of the Securities.

          4. Payment and Delivery. Payment for the Securities shall be made to the Company in Federal or other funds immediately available in New York City against delivery of such Securities at 9:00 a.m., New York City time, on September 14, 2009, or at such other time on the same or such other date, not later than September 22, 2009, as shall be designated in writing by you. The time and date of such payment are hereinafter referred to as the “ Closing Date .”

          Certificates for the Securities shall be in global form and registered in such names and in such denominations as you shall request in writing not later than one full business day prior to the Closing Date. The certificates evidencing the Securities shall be delivered to you on the Closing Date for the respective accounts of the several Underwriters, with any transfer taxes payable in connection with the transfer of the Securities to the Underwriters duly paid, against payment of the Purchase Price therefor plus accrued interest, if any, to the date of payment and delivery.

          5. Covenants of the Company. In further consideration of the agreements of the Underwriters herein contained, the Company covenants with each Underwriter as follows:

     (a) The Company has filed or will file each Statutory Prospectus (including the Prospectus) with the Commission pursuant to and in accordance with Rule 424(b) not later than the second business day following the earlier of the date it is first used or the execution and delivery of this Agreement. The Company has complied and will comply with Rule 433 of the Rules and Regulations.

     (b) The Company will advise the Representatives promptly of any proposal to amend or supplement the Registration Statement, the Prospectus or the General Disclosure Package and will afford the Representatives a reasonable opportunity to comment on any such proposed amendment or supplement; provided , however , the Company shall not file any such proposed amendment or supplement to which the Representatives rea