OBJECTIVE To assess whether simultaneous operations are appropriate for combined thoracic and abdominal aortic aneurysms. METHODS Simultaneous operations were performed for combined thoracic and abdominal aortic aneurysms in nine patients. The thoracic aortic aneurysm (TAA) was repaired first, followed by repair of the abdominal aortic aneurysm (AAA). Selective cerebral perfusion was used in eight patients, after the exception of one who underwent replacement of the ascending aorta under hypothermic circulatory arrest. The abdominal organs were perfused during distal anastomosis in surgery for Stanford type A aortic dissection or aortic arch aneurysm; via the femoral artery with an aortic balloon occlusion catheter in one patient, and via an occlusion catheter with a perfusion lumen in two patients. RESULTS All patients underwent planned simultaneous repair of the AAA. One of the patients who underwent simultaneous replacement of both the descending thoracic and abdominal aorta was left with paraplegia, and one patient died suddenly of massive hemoptysis and melena on the 29th postoperative day. Autopsy revealed that the bleeding had been caused by aorto-broncho-esophageal fistulae. The overall operative mortality was 11%. CONCLUSIONS Simultaneous repair of combined TAA and AAA can be safely performed; however, the risk of paraplegia should be considered, especially with simultaneous repair of concomitant aneurysms of the descending thoracic and abdominal aorta.