The term "penetrating aortic ulcer" refers to an ulceration of an atheromatous plaque that extends deeply through the intima and into the aortic media. It may precipitate an intramedial dissection (usually localized) or may rupture into the adventitia to form a pseudoaneurysm. The typical patient with penetrating atheromatous aortic ulcer is elderly and has hypertension, atherosclerosis, and back or chest pain, but pulse deficit, stroke, aortic insufficiency, and compromise of a visceral vessel are not present. Classic aortic dissection and symptomatic thoracic aortic aneurysms are among possibilities in the differential diagnosis. Aortography demonstrates the presence of an aortic ulcer similar in appearance to gastric ulcers seen on barium examination; in addition, an intramural aortic hematoma may be present. Our experience with penetrating aortic ulcers in symptomatic patients indicates that conservative medical therapy leads to recurrence of symptoms and a need for surgical intervention. We present a case that illustrates the salient features of this distinct clinical entity.