A 23-year-old female self-contained underwater breathing apparatus (SCUBA) diver developed central nervous symptoms and signs of arterial gas embolism when surfacing after 15 min at a depth of 18 m. The dive had been performed according to normal procedure. In the hospital, chest X-ray and computer tomography of the chest showed a large emphysematous bulla in the left hemithorax. Recompression treatment was not performed. Reexamination of old X-rays showed an emphysematous bulla on the left side which had been present before the dive. She made a complete recovery. Emphysematous bullae may be a more common cause of pulmonary barotrauma than is realised. Bullae visible on computer tomograms or magnetic resonance imaging may not be visible on conventional X-rays. The case reported illustrates the need for a consensus on the procedures necessary for the medical screening of diving candidates.