A 40-year-old female had right-sided pneumothorax. She was treated with a chest tube. On the 2nd day, her menstruation started. Because of a persistent air leak, she underwent a thoracoscopic operation on the 15th day. During the operation, we noted a pulmonary bulla at the apex and multiple blue berry spots both on the visceral pleura and the tendinous part of the diaphragm. We performed a resection of the pulmonary bulla, partial diaphragmatic excision plus suture. Section of visceral pleura and diaphragm shows ductal structures, which is insistent with endometriosis. The serum CA125 level decreased to 39 U/ml. Following surgery, oral contraceptives was started and no recurrence was encountered thereafter.