GUARANTEE AGREEMENT

Exhibit 4.2

GUARANTEE AGREEMENT

AMERICANWEST BANCORPORATION

Dated as of [              ,] 2008

TABLE OF CONTENTS

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GUARANTEE AGREEMENT

This GUARANTEE AGREEMENT (the “Guarantee”), dated as of              , 2008, is executed and delivered by AmericanWest Bancorporation, a bank holding company incorporated in Washington (the “Guarantor”), and Wilmington Trust Company, a Delaware banking corporation, as trustee (the “Guarantee Trustee”), for the benefit of the Holders (as defined herein) from time to time of the Capital Securities (as defined herein) of AmericanWest Capital Trust IV, a Delaware statutory trust (the “Issuer”).

WHEREAS , pursuant to an Amended and Restated Declaration of Trust (the “Declaration”), dated as of              , 2008, among the trustees named therein of the Issuer, AmericanWest Bancorporation, as sponsor, and the holders from time to time of undivided beneficial interests in the assets of the Issuer, the Issuer is issuing on the date hereof fixed rate trust preferred securities, having an aggregate liquidation amount of $[30,000,000] (the “Capital Securities”); and

WHEREAS , the Capital Securities will be issued by the Issuer, and the proceeds thereof, together with the proceeds from the issuance of the Issuer’s common securities, will be used to purchase the Debentures (as defined herein);

WHEREAS , as incentive for the Holders to purchase the Capital Securities, the Guarantor desires irrevocably and unconditionally to agree, to the extent set forth in this Guarantee, to pay to the Holders of Capital Securities the Guarantee Payments (as defined herein) and to make certain other payments on the terms and conditions set forth herein.

NOW, THEREFORE , in consideration of the purchase by each Holder of the Capital Securities, which purchase the Guarantor hereby agrees shall benefit the Guarantor, the Guarantor executes and delivers this Guarantee for the benefit of the Holders from time to time of the Capital Securities:

ARTICLE I

DEFINITIONS AND INTERPRETATION

SECTION 1.1 Definitions and Interpretation .

In this Guarantee, unless the context otherwise requires:

(a) capitalized terms used in this Guarantee but not defined in the preamble above have the respective meanings assigned to them in this Section 1.1;

(b) a term defined anywhere in this Guarantee has the same meaning throughout;

(c) all references to “the Guarantee” or “this Guarantee” are to this Guarantee as modified, supplemented or amended from time to time;

(d) all references in this Guarantee to Articles and Sections are to Articles and Sections of this Guarantee, unless otherwise specified;

(e) capitalized terms used in this Guarantee but not defined herein have the meanings assigned to such terms in the Declaration as of the date of execution of this Guarantee; and

(f) a reference to the singular includes the plural and vice versa.

“Beneficiary” means any Person to whom the Issuer is or hereafter becomes indebted or liable.

“Common Securities” has the meaning specified in the Declaration.

“Corporate Trust Office” means the office of the Guarantee Trustee at which at any particular time its corporate trust business shall be principally administered, which at all times shall be located within the United States and at the time of the execution of this Guarantee shall be Rodney Square North, 1100 North Market Street, Wilmington, DE 19890-0001.

“Debenture Issuer” means AmericanWest Bancorporation or any successor entity resulting from any consolidation, amalgamation, merger or other business combination, in its capacity as issuer of the Debentures.

“Debentures” means the junior subordinated debentures of the Debenture Issuer that are designated in the Indenture as the “Fixed Rate Junior Subordinated Debt Securities due 2038” and held by the Institutional Trustee (as defined in the Declaration) of the Issuer.

“Event of Default” has the meaning set forth in Section 2.4.

“Guarantee Payments” means the following payments or distributions, without duplication, with respect to the Capital Securities, to the extent not paid or made by or on behalf of the Issuer: (i) any accrued and unpaid Distributions (as defined in the Declaration) which are required to be paid on such Capital Securities, to the extent the Issuer has funds available in the Property Account (as defined in the Declaration) therefor at such time, (ii) the price payable upon the redemption of any Capital Securities to the extent the Issuer has funds available in the Property Account therefor at such time, and (iii) upon a voluntary or involuntary liquidation, dissolution, winding-up or termination of the Issuer (other than in connection with the distribution of Debentures to the Holders in exchange therefor as provided in the Declaration), the lesser of (a) the aggregate of the liquidation amount of the Capital Securities and all accrued and unpaid Distributions on the Capital Securities to the date of payment, to the extent the Issuer has funds available in the Property Account therefor at such time, and (b) the amount of assets of the Issuer remaining available for distribution to Holders in liquidation of the Issuer after satisfaction of liabilities to creditors of the Issuer as required by applicable law (in either case, the “Liquidation Distribution”).

“Guarantee Trustee” means Wilmington Trust Company, until a Successor Guarantee Trustee has been appointed and has accepted such appointment pursuant to the terms of this Guarantee and thereafter means each such Successor Guarantee Trustee.

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“Holder” means any Person in whose name any Capital Securities are registered on the books and records of the Issuer; provided , however , that, in determining whether the holders of the requisite percentage of Capital Securities have given any request, notice, consent or waiver hereunder, “Holder” shall not include the Guarantor, the Guarantee Trustee or any Affiliate of the Guarantor or Guarantee Trustee.

“Indemnified Person” means the Guarantee Trustee (including in its individual capacity), any Affiliate of the Guarantee Trustee, or any officers, directors, shareholders, members, partners, employees, representatives, nominees, custodians or agents of the Guarantee Trustee.

“Indenture” means the Indenture, dated as of              , 2008, between the Debenture Issuer and Wilmington Trust Company, not in its individual capacity but solely as trustee, and any indenture supplemental thereto pursuant to which the Debentures are to be issued to the Institutional Trustee of the Issuer.

“Liquidation Distribution” has the meaning set forth in the definition of “Guarantee Payments” herein.

“Majority in liquidation amount of the Capital Securities” means Holder(s) of outstanding Capital Securities, voting together as a class, but separately from the holders of Common Securities, of more than 50% of the aggregate liquidation amount (including the amount that would be paid upon the redemption, liquidation or otherwise on the date upon which the voting percentages are determined, plus unpaid Distributions accrued thereon to such date) of all Capital Securities then outstanding.

“Obligations” means any costs, expenses or liabilities (but not including liabilities related to taxes) of the Issuer, other than obligations of the Issuer to pay to holders of any Trust Securities the amounts due such holders pursuant to the terms of the Trust Securities.

“Officer’s Certificate” means, with respect to any Person, a certificate signed by one Authorized Officer of such Person. Any Officer’s Certificate delivered with respect to compliance with a condition or covenant provided for in this Guarantee shall include:

(a) a statement that such officer signing the Officer’s Certificate has read the covenant or condition and the definitions relating thereto;

(b) a brief statement of the nature and scope of the examination or investigation undertaken by such officer in rendering the Officer’s Certificate;

(c) a statement that such officer has made such examination or investigation as, in such officer’s opinion, is necessary to enable such officer to express an informed opinion as to whether or not such covenant or condition has been complied with; and

(d) a statement as to whether, in the opinion of such officer, such condition or covenant has been complied with.

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“Person” means a legal person, including any individual, corporation, estate, partnership, joint venture, association, joint stock company, limited liability company, trust, unincorporated association, or government or any agency or political subdivision thereof, or any other entity of whatever nature.

“Responsible Officer” means, with respect to the Guarantee Trustee, any officer within the Corporate Trust Office of the Guarantee Trustee with direct responsibility for the administration of any matters relating to this Guarantee, including any vice president, any assistant vice president, any secretary, any assistant secretary, the treasurer, any assistant treasurer, any trust officer or other officer of the Corporate Trust Office of the Guarantee Trustee customarily performing functions similar to those performed by any of the above designated officers and also means, with respect to a particular corporate trust matter, any other officer to whom such matter is referred because of that officer’s knowledge of and familiarity with the particular subject.

“Successor Guarantee Trustee” means a successor Guarantee Trustee possessing the qualifications to act as Guarantee Trustee under Section 3.1.

“Trust Securities” means the Common Securities and the Capital Securities.

ARTICLE II

POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

SECTION 2.1 Powers and Duties of the Guarantee Trustee .

(a) This Guarantee shall be held by the Guarantee Trustee for the benefit of the Holders, and the Guarantee Trustee shall not transfer this Guarantee to any Person except a Holder exercising its rights pursuant to Section 4.4 (b) or to a Successor Guarantee Trustee on acceptance by such Successor Guarantee Trustee of its appointment to act as Successor Guarantee Trustee. The right, title and interest of the Guarantee Trustee shall automatically vest in any Successor Guarantee Trustee, and such vesting and cessation of title shall be effective whether or not conveyancing documents have been executed and delivered pursuant to the appointment of such Successor Guarantee Trustee.

(b) In case an Event of Default has occurred (that has not been cured or waived pursuant to Section 2.4(b)) and is actually known to a Responsible Officer of the Guarantee Trustee, the Guarantee Trustee shall enforce this Guarantee for the benefit of the Holders, exercising such of the rights and powers vested in it by this Guarantee, and using the same degree of care and skill in its exercise thereof, as a prudent person would exercise or use under the circumstances in the conduct of his or her own affairs.

(c) No provision of this Guarantee shall be construed to relieve the Guarantee Trustee from liability for its own negligent action, its own negligent failure to act, or its own willful misconduct or bad faith, except that:

(i) prior to the occurrence of any Event of Default and after the curing or waiving of all Events of Default that may have occurred:

(A) the duties and obligations of the Guarantee Trustee shall be determined solely by the express provisions of this Guarantee, and the Guarantee Trustee shall not be liable except for the performance of such duties and obligations as are specifically set forth in this Guarantee, and no implied covenants or obligations shall be read into this Guarantee against the Guarantee Trustee; and

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(B) in the absence of bad faith on the part of the Guarantee Trustee, the Guarantee Trustee may conclusively rely, as to the truth of the statements and the correctness of the opinions expressed therein, upon any certificates or opinions furnished to the Guarantee Trustee and conforming to the requirements of this Guarantee; but in the case of any such certificates or opinions furnished to the Guarantee Trustee, the Guarantee Trustee shall be under a duty to examine the same to determine whether or not on their face they conform to the requirements of this Guarantee;

(ii) the Guarantee Trustee shall not be liable for any error of judgment made in good faith by a Responsible Officer of the Guarantee Trustee, unless it shall be proved that such Responsible Officer of the Guarantee Trustee or the Guarantee Trustee was negligent in ascertaining the pertinent facts upon which such judgment was made;

(iii) the Guarantee Trustee shall not be liable with respect to any action taken or omitted to be taken by it in good faith in accordance with the written direction of the Holders of a Majority in liquidation amount of the Capital Securities relating to the time, method and place of conducting any proceeding for any remedy available to the Guarantee Trustee, or exercising any trust or power conferred upon the Guarantee Trustee under this Guarantee; and

(iv) no provision of this Guarantee shall require the Guarantee Trustee to expend or risk its own funds or otherwise incur personal financial liability in the performance of any of its duties or in the exercise of any of its rights or powers, if the Guarantee Trustee shall have reasonable grounds for believing that the repayment of such funds is not reasonably assured to it under the terms of this Guarantee, or security and indemnity, reasonably satisfactory to the Guarantee Trustee, against such risk or liability is not reasonably assured to it.

SECTION 2.2 Certain Rights of the Guarantee Trustee .

(a) Subject to the provisions of Section 2.1:

(i) The Guarantee Trustee may conclusively rely, and shall be fully protected in acting or refraining from acting, upon any resolution, certificate, statement, instrument, opinion, report, notice, request, direction, consent, order, bond, debenture, note, other evidence of indebtedness or other paper or document believed by it to be genuine and to have been signed, sent or presented by the proper party or parties.

(ii) Any direction or act of the Guarantor contemplated by this Guarantee shall be sufficiently evidenced by an Officer’s Certificate.

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(iii) Whenever, in the administration of this Guarantee, the Guarantee Trustee shall deem it desirable that a matter be proved or established before taking, suffering or omitting any action hereunder, the Guarantee Trustee (unless other evidence is herein specifically prescribed) may, in the absence of bad faith on its part, request and conclusively rely upon an Officer’s Certificate of the Guarantor which, upon receipt of such request, shall be promptly delivered by the Guarantor.

(iv) The Guarantee Trustee shall have no duty to see to any recording, filing or registration of any instrument or other writing (or any rerecording, refiling or reregistration thereof).

(v) The Guarantee Trustee may consult with counsel, and the advice or opinion of such counsel shall be full and complete authorization and protection in respect of any action taken, suffered or omitted by it hereunder in good faith and in accordance with such advice or opinion. Such counsel may be counsel to the Guarantee Trustee, the Guarantor or any of its Affiliates and may be one of its employees. The Guarantee Trustee shall have the right at any time to seek instructions concerning the administration of this Guarantee from any court of competent jurisdiction.

(vi) The Guarantee Trustee shall be under no obligation to exercise any of the rights or powers vested in it by this Guarantee at the request or direction of any Holder, unless such Holder shall have provided to the Guarantee Trustee such security and indemnity, reasonably satisfactory to the Guarantee Trustee, against the costs, expenses (including attorneys’ fees and expenses and the expenses of the Guarantee Trustee’s agents, nominees or custodians) and liabilities that might be incurred by it in complying with such request or direction, including such reasonable advances as may be requested by the Guarantee Trustee; provided, however, that nothing contained in this Section 2.2(a)(vi) shall be taken to relieve the Guarantee Trustee, upon the occurrence of an Event of Default, of its obligation to exercise the rights and powers vested in it by this Guarantee.

(vii) The Guarantee Trustee shall not be bound to make any investigation into the facts or matters stated in any resolution, certificate, statement, instrument, opinion, report, notice, request, direction, consent, order, bond, debenture, note, other evidence of indebtedness or other paper or document, but the Guarantee Trustee, in its discretion, may make such further inquiry or investigation into such facts or matters as it may see fit.

(viii) The Guarantee Trustee may execute any of the trusts or powers hereunder or perform any duties hereunder either directly or by or through agents, nominees, custodians or attorneys, and the Guarantee Trustee shall not be responsible for any misconduct or negligence on the part of any agent or attorney appointed with due care by it hereunder.

(ix) Any action taken by the Guarantee Trustee or its agents hereunder shall bind the Holders of the Capital Securities, and the signature of the Guarantee Trustee or its agents alone shall be sufficient and effective to perform any such action.

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No third party shall be required to inquire as to the authority of the Guarantee Trustee to so act or as to its compliance with any of the terms and provisions of this Guarantee, both of which shall be conclusively evidenced by the Guarantee Trustee’s or its agent’s taking such action.

(x) Whenever in the administration of this Guarantee the Guarantee