A 55-year-old women with von Recklinghausen's disease was admitted to our hospital after sudden left-sided chest pain. She became shocked with a blood pressure of 50mmHg and pulse of 120per min. Chest radiography showed a massive left pleural effusion. Thoracentesis revealed bright blood. Emergency operation was perfomed. The source of bleeding was not clearly identified, but we suspected rupture of the intercostal artery. So we resected a part of descending aorta and implanted a Dacron graft. The bleeding was stopped. She discharged about five months later because of post-operative respiratory and hepatic failure. Histological examination of the aortic wall revealed extensive adventitial infiltration with neurofibromas. The turbulance of the aortic medial elastic fiber was also observed. We considered these histological change of the vessel caused spontaneous rupture of the intercostal artery.