There are over a million certified sport scuba divers in the United States today. The sport is growing at an average annual rate of 7%. The vast majority of medical problems associated with scuba diving are related to the head and neck area, especially the ears. This paper provides an update on the physiology and pathophysiology of sport scuba diving. It also offers guidelines for the physician who may be called upon to examine candidates for the sport or to make decisions on continued diving for trained sport divers.