Thromboexclusion method for thoracic aortic aneurysm was studied in 10 patients who had dissecting aneurysm in 7 and atherosclerotic aneurysm in 3. The aortic aneurysms extended from the left subclavian artery to the diaphragma or more widely. The operations were extraanatomic bypass and permanent aortic clamp proximal to the aneurysm in 9, and proximal and distal to the aneuysm in one. The follow up periods were 14 days to 80 months. Eight patients survived more than 3 months and 5 of them had thromboexclusion of aneurysm to the diaphragma. One with the aneurysms of incomplete thromboexclusion resulted in aneurysmal rupture 28 months after operation, and recovered by additional clamp distal to the aneurysm. Another had aneurysmal rupture, and died 63 months after operation. A patient had the penetration of the clamp to the pulmonary artery, and died 12 months after operation. Temporary paraplegia occurred in a patient 15 months after operation. Two patients developed constipation without ileus. Any difference of blood pressure between upper and lower extremities was not recognized, and no patient had deterioration of renal function. Indication of this method should be strictly selected, and careful follow up study is mandatory.