Some hospital chains may use big profits from their premier hospitals to finance empire building around the country. The Mayo Clinic's two main hospitals in RochesterRochester Methodist Hospital (No. 3 on the list) and St. Mary's Hospital (No. 25)-are both enormously profitable. Yet the Mayo Clinic overall is only modestly profitable, according to its financial statements. Where does all that money go? A spokeswoman for Mayo had no comment.