Sheehan, who is currently Bisys' president and COO, will assume the CEO position on January 1 2003.
Prior to joining the company, Sheehan held various executive management roles with Concord Holdings Corporation, The Equitable and Paine Webber.
Lynn Mangum will continue as Bisys' chairman and chief executive officer for the remainder of the year and will then be employed as chairman of the board of directors.