EXHIBIT 4.1 NUMBER [MB FINANCIAL LOGO] SHARES MB INCORPORATED UNDER THE LAWS CUSIP 55263D 10 7 OF THE STATE OF DELAWARE SEE REVERSE FOR COMMON STOCK PAR VALUE $.01 PER SHARE CERTAIN DEFINITIONS THIS CERTIFICATE IS TRANSFERABLE IN THE CITY OF CHICAGO OR IN THE CITY OF NEW YORK THIS CERTIFIES THAT IS THE OWNER OF FULLY PAID AND NONASSESSABLE SHARES OF COMMON STOCK, PAR VALUE $.01 PER SHARE OF MB FINANCIAL, INC. (THE "CORPORATION"), A DELAWARE CORPORATION. THE SHARES REPRESENTED BY THIS CERTIFICATE ARE TRANSFERABLE ONLY ON THE STOCK TRANSFER BOOKS OF THE CORPORATION BY THE HOLDER OF RECORD HEREOF, OR BY HIS DULY AUTHORIZED ATTORNEY OR LEGAL REPRESENTATIVE, UPON THE SURRENDER OF THIS CERTIFICATE PROPERLY ENDORSED. THE CERTIFICATE IS NOT VALID UNTIL COUNTERSIGNED AND REGISTERED BY THE CORPORATION'S TRANSFER AGENT AND REGISTRAR. THIS SECURITY IS NOT A DEPOSIT OR ACCOUNT AND IS NOT LEGALLY, INSURED OR GUARANTEED. IN WITNESS WHEREOF THE CORPORATION HAS CAUSED THIS CERTIFICATE TO BE EXECUTED BY THE FACSIMILE SIGNATURES OF ITS DULY AUTHORIZED OFFICER AND HAS CAUSED A FACSIMILE OF ITS CORPORATE SEAL TO BE HEREUNTO AFFIXED. DATED MITCHELL FEIGER ----------------------- PRESIDENT AND CHIEF EXECUTIVE OFFICER COUNTERSIGNED AND REGISTERED LASALLE NATIONAL BANK (CHICAGO) TRANSFER AGENT MB FINANCIAL INC. DORIA L. KORIS AND REGISTRAR CORPORATE SEAL SECRETARY 1993 DELAWARE AUTHORIZED SIGNATURE 134