Although pulmonary barotrauma (PBT) is a well-known clinical entity, its recognition in divers is sometimes delayed and its implications for future diving often are unappreciated. The pulmonary complications of diving activities range from mere discomfort from mediastinal emphysema or pneumothorax, or both, to life-threatening gas embolization. In nine cases described here, only minor manifestations were associated with PBT which occurred at or close to the surface, but three of these four divers were found to have abnormal pulmonary function. More serious manifestations resulted from PBT which took place at depths of 16 to 120 ft. Even minor forms of PBT should be considered a contraindication to further diving, since they are prone to recur. Such recurrences--even at shallow depths--may cause serious complications.