Objective: Penetrating atherosclerotic ulcer (PAU) of the aorta is defined as an atherosclerotic lesion with ulceration of the aortic intima and media and rupture of the internal elastic lamina. PAU induced aortic dissection, aortic rupture, and secular aortic aneurysm and typically occurs in elderly hypertensive patients with severe atherosclerosis. Although it has been reported that atherosclerosis similarly occurs in the abdominal aorta, its natural history and treatment are still unclear. This study investigated the clinical features, natural history, and treatment of PAU of the abdominal aorta.