The document(s) containing the information specified in Part I of Form S-8 will be sent or given to holders of outstanding stock options, restricted stock units and director stock units under the First Oak Brook Bancshares, Inc. Incentive Compensation Plan, First Oak Brook Bancshares, Inc. 2001 Stock Incentive Plan and First Oak Brook Bancshares, Inc. Directors Stock Plan, as required by Rule 428(b)(1) promulgated by the Securities and Exchange Commission (the "Commission") under the Securities Act of 1933, as amended (the "Securities Act").

              Such document(s) are not being filed with the Commission, but constitute (along with the documents incorporated by reference into the Registration Statement pursuant to Item 3 of Part II hereof) a prospectus that meets the requirements of Section 10(a) of the Securities Act.

Item 3.   Incorporation of Certain Documents by Reference.

              The following documents previously or concurrently filed by MB Financial, Inc. (the "Company") with the Commission (File No. 0-24566-01) are hereby incorporated by reference into this Registration Statement and the Prospectus to which this Registration Statement relates (the "Prospectus"):

              All documents filed by the Company with the Commission pursuant to Sections 13(a), 13(c), 14, or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act"), after the filing of this Registration Statement, and prior to the filing of a post-effective amendment which indicates that all securities offered hereby have been sold or which deregisters all securities then remaining unsold, shall be deemed incorporated by reference into this Registration Statement and the Prospectus and to be a part hereof and thereof from the date of the filing of such documents. Any statement contained in the documents incorporated, or deemed to be incorporated, by reference herein or therein shall be deemed to be modified or superseded for purposes of this Registration Statement and the Prospectus to the extent that a statement contained herein or therein or in any other subsequently filed document which also is, or is deemed to be, incorporated by reference herein or therein modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this Registration Statement and the Prospectus.

              The Company shall furnish without charge to each person to whom the Prospectus is delivered, on the written or oral request of such person, a copy of any or all of the documents incorporated by reference, other than exhibits to such documents (unless such exhibits are specifically incorporated by reference to the information that is incorporated). Requests should be directed to: Doria Koros, Secretary, MB Financial, Inc., 6111 North River Road, Rosemont, Illinois 60018, telephone number (847) 653-1992.

              Not Applicable.

Item 5.   Interests of Named Experts and Counsel.

              Not Applicable.

Item 6.   Indemnification of Directors and Officers.

              Section 2-405.2 of the Maryland General Corporation Law permits a Maryland corporation to include in its charter a provision limiting the liability of its directors and officers to the corporation and its stockholders for monetary damages except: (1) to the extent it is proven that the director or officer actually received an improper benefit or profit, for the amount of the improper benefit or profit; or (2) to the extent a final judgment or adjudication against the director or officer is based on a determination that the director's or officer's act or failure to act was the result of active and deliberate dishonesty and was material to the cause of action against the director or officer. The Registrant's charter contains such a provision, thereby limiting the liability of its directors and officers to the maximum extent permitted by Maryland law.

              Section 2-418 of the Maryland General Corporation Law permits a Maryland corporation to indemnify a director or officer who is made a party to any proceeding by reason of service in that capacity against judgments, penalties, fines, settlements and reasonable expenses actually incurred unless it is proven that: (1) the act or omission of the director or officer was material to the matter giving rise to the proceeding and was committed in bad faith or with active and deliberate dishonesty; (2) the director or officer actually received an improper personal benefit; or (3) in the case of a criminal proceeding, the director or officer had reason to believe that his conduct was unlawful. The Maryland General Corporation Law provides that where a director or officer is a defendant in a proceeding by or in the right of the corporation, the director or officer may not be indemnified if he or she is found liable to the corporation. The Maryland General Corporation Law also provides that a director or officer may not be indemnified in respect of any proceeding alleging improper personal benefit in which he or she was found liable on the grounds that personal benefit was improperly received. A director or officer found liable in a proceeding by or in the right of the corporation or in a proceeding alleging improper personal benefit may petition a court to nevertheless order indemnification for expenses if the court determines that the director or officer is fairly and reasonably entitled to indemnification in view of all the relevant circumstances.

              Section 2-418 of the Maryland General Corporation Law provides that unless limited by the charter of a Maryland corporation, a director or officer who is successful on the merits or otherwise in defense of any proceeding must be indemnified against reasonable expenses. Section 2-418 also provides that a Maryland corporation may advance reasonable expenses to a director or officer upon the corporation's receipt of (a) a written affirmation by the director or officer of his or her good faith belief that he or she has met the standard of conduct necessary for indemnification by the corporation and (b) a written undertaking by the director or officer or on his or her behalf to repay the amount paid or reimbursed by the corporation if it is ultimately determined that the standard of conduct was not met.

              The Registrant's charter provides for indemnification of directors and officers to the maximum extent permitted by the Maryland General Corporation Law.

              Under a directors' and officers' liability insurance policy, directors and officers of the Registrant are insured against certain liabilities.

Item 7.   Exemption from Registration Claimed.

              Not applicable.

Item 8.   Exhibits.

              See Exhibit Index.

Item 9.   Undertakings.

              Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Chicago, State of Illinois, on August 30, 2006.

              We, the undersigned officers and directors of MB Financial, Inc., hereby severally and individually constitute and appoint Mitchell Feiger and Jill E. York, and each of them, the true and lawful attorneys and agents of each of us to execute in the name, place and stead of each of us (individually and in any capacity stated below) any and all amendments (including post-effective amendments) to this registration statement and all instruments necessary or advisable in connection therewith and to file the same with the Securities and Exchange Commission, each of said attorneys and agents to have the power to act with or without the others and to have full power and authority to do and perform in the name and on behalf of each of the undersigned every act whatsoever necessary or advisable to be done in the premises as fully and to all intents and purposes as any of the undersigned might or could do in person, and we hereby ratify and confirm our signatures as they may be signed by our said attorneys and agents or each of them to any and all such amendments and instruments.

              Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.