Five cases of traumatic aneurysm of the thoracic aorta associated with blunt chest trauma are described. Although we lost one case, four cases were successfully treated. Case 1, This was a 22-year-old female who underwent surgery for graft replacement of the descending thoracic aorta under extracorporeal circulation two days after injury. Case 2, This was a 17-year-old male who underwent surgery for graft replacement of the descending thoracic aorta under extracorporeal circulation 24 hours after injury. Case 3, This was a 56-year-old female who underwent surgery for graft replacement of the descending thoracic aorta under extracorporeal circulation 24 hours after injury. Case 4, This was a 69-year-old male who underwent surgery for graft replacement with three branches for an aortic arch aneurysm under extracorporeal circulation one month after injury. Despite an emergency operation, we lost case 5 (a 21-year-old male) because of a complete discontinuity of the aortic isthmus. The postoperative course of the other four cases was uneventful. Vessel injury may be more widespread than preoperative radiographic findings demonstrates. Blunt chest trauma is usually accompanied by multisystem injury. Therefore, it is imperative to determine the first priority of treatment based on further preoperative examination in cases having associated injuries.