MB Financial and First Oak Brook Bancshares to Merge

Business Wire, May 2, 2006

CHICAGO -- MB Financial, Inc. (Nasdaq:MBFI) and First Oak Brook Bancshares, Inc. (Nasdaq:FOBB) announced the signing of a definitive merger agreement. Under the Agreement, MB Financial will acquire First Oak Brook. First Oak Brook is a bank holding company headquartered in Oak Brook, Illinois with $2.3 billion in assets, $1.9 billion in deposits and 21 full-service branches in Chicago.

The merger will significantly increase MB Financial's presence in the attractive Chicagoland banking market. Combined with First Oak Brook, MB Financial will have over $8.2 billion in assets and 61 Chicago area locations.

"First Oak Brook's strong deposit gathering expertise combined with MB Financial's proven asset origination capability will create a company that has the potential to grow earning assets at double-digit rates while funding them organically -- a truly powerful combination in an industry where net interest income continues to be the main earnings growth engine," stated Mitchell Feiger, President and Chief Executive Officer of MB Financial.

"Our companies complement each other exceptionally well in terms of talent, geographic coverage and business orientation," Mr. Feiger continued. "We are truly excited about the opportunities for our combined company."

"This merger means great things for First Oak Brook employees, shareholders and customers," stated Richard M. Rieser, Jr., First Oak Brook President and Chief Executive Officer. "Customers will have access to a deep and broad array of banking services across a larger geographic footprint. Since there is little overlap between our footprints, our customers will continue to do business with the people they know and trust. MB's commercial lending and leasing expertise and earnings power will provide us with extra resources to continue to expand our retail and community banking presence and meet the needs of our commercial and public clients, particularly in our centers of influence in the western suburbs and North Shore of Chicago."

The merger will also increase MB Financial's scale in a number of business lines including treasury management, merchant processing, asset management, trust, private banking, investment services and leasing.

Mr. Feiger also noted, "Together, we will enhance our commercial business in Chicago's middle market -- one of the most profitable customer segments in banking. Our combined branches provide us with strong market share in both DuPage and Cook Counties where almost 80% of Chicago MSA middle-market businesses are located."

Based on MB Financial's average closing price for the five-day period ended April 28th, the transaction is valued at $36.80 per First Oak Brook share, for a transaction value of approximately $372 million, exclusive of stock options. At closing, First Oak Brook shareholders will receive, in exchange for each share of First Oak Brook common stock they hold, consideration with a value equal to the sum of (1) 0.8304 multiplied by the average of the closing prices for MB Financial common stock during the five trading days ending the day before the completion of the merger and (2) $7.36, representing an aggregate consideration mix of approximately 80% MB Financial stock and 20% cash. Under the terms of the merger agreement, each holder of First Oak Brook common stock will be entitled to elect to receive their merger consideration in the form of MB Financial common stock, cash or a combination of both, subject to limitations and prorations. Receipt of shares of MB Financial stock in the merger is expected to be tax-free.

The merger, is subject to regulatory approvals, approval by MB Financial stockholders of the issuance of MB Financial shares in the merger, and approval by First Oak Brook stockholders, and is expected to close in the fourth quarter of 2006. The merger is expected to be immediately accretive to MB Financial's annual GAAP and cash EPS.

Following the merger Mr. Rieser and Mr. Charles Gries from First Oak Brook's board will join the MB Financial Board. Mr. Rieser will continue in his current capacity until the transaction closes; at that time, he will become Vice Chairman and Executive Vice President of MB Financial, Inc.

The definitive agreement was unanimously approved by the boards of MB Financial and First Oak Brook, and the directors have executed agreements to vote their shares in favor of the transaction.

Goldman, Sachs & Co. is acting as financial advisor to MB Financial and Silver, Freedman & Taff LLP is serving as its legal counsel with respect to the transaction. First Oak Brook is being advised by Keefe, Bruyette & Woods Inc. and Vedder, Price, Kaufman & Kammholz, P.C. is acting as its legal counsel.

MB Financial, Inc. is the $5.9 billion Chicago-based holding company for its lead bank, MB Financial Bank, N.A., and Union Bank, N.A. (Oklahoma). MB Financial Bank also owns LaSalle Systems Leasing, Inc. and Vision Investment Services, Inc., a registered broker/dealer.

MB Financial Bank (www.mbfinancial.com) is a leader among Chicago area banks and has been delivering competitive personalized service for more than 90 years to privately owned, middle-market companies as well as to individuals who live and work in the communities where its branches are located. MB Financial Bank currently has 40 branches strategically located throughout the Chicago area.