Thirteen cases of ruptured abdominal aortic aneurysm were treated during a period of 7 years and 5 months. In 6 cases, left thoracotomy was used before laparotomy to clamp the descending thoracic aorta. The merits and demerits of this method were evaluated in this study. It is useful for early improvement of cerebral and coronary circulation and prevention of sudden spurting hemorrhage, especially in cases with the previous laparotomies. On the other hand, this method has a shorter clamp time limit and requires much time in cases with pleural adhesions. It may increase the amount of operative bleeding and the incidence of postoperative respiratory insufficiency. It may also cause an intraoperative thoracic aortic dissection and rupture of thoracic aortic aneurysms if present. It is considered that this method is advantageous, but should be used only in selected cases.