For the past 20 years, US businesses have lost an average of $11.3 billion a year to failed mergers and acquisitions. The failures cross market cycles, industries, and deal size. These "business marriages" are costly not only because they destroy value-they diminish market share, damage business relationships, and tarnish once-respected brands. The author interviewed 100 M&A experts in varying deal roles to determine the underlying causes for the persistently poor track record. The experts strongly agree that failure to assess the cultures of the prospective partners prior to deal close often...