Catamenial pneumothorax is a relatively rare condition, generally of mild to moderate severity. We report the case of a 29-year-old woman who experienced an episode of life threatening right-sided hemopneumothorax in association with menses. She had already been operated on for recurrent pneumothorax. Treatment of the current episode included urgent tube thoracostomy and iterative thoracotomy, together with lung wedge resection, parietal pleurectomy, and partial diaphragmatic excision. Pathologic examination revealed endometrial implants massively involving the diaphragm, the pleura, and the lung parenchyma. The present report shows that endometriosis-related pneumothorax may be extremely severe. The multiple localizations of endometrial implants in this case may provide a support to the different pathogenic theories of endometriosis-related pneumothorax.