An aortic aneurysm is described as a permanent localized dilatation of the aorta having a diameter at least 1.5 times that of the expected norrnal diameter of that given aortic segment. Thoracic aortic aneurysms are much less common than are aneurysms of the abdominal aorta. Thoracic aneurysms are classified by the portion of aorta involved, I.e., the ascending, arch, or descending thoracic aorta. We experienced a case of saccular arteriosclerotic aortic aneurysm associated with thrombus in aortic arch in a 78 year-old male who had history of hypertension. He was admitted to Kwangju Veterans Hospital complaining of drowsy mental state and swelling of left foreann. The chest X-ray, chest CT and echocardiogram showed saccular dilatation(maximal diarneter ; 7.67~7.86cm) associated with thrombus in aortic arch. He refused operation because of old age, so he was conservatively rnanaged including propranolol. We report this case of saccular arteriosclerotic aneurysm of aortic arch with a brief review of literature.