Penetrating atherosclerotic aortic ulceration is a unique disease with distinct management and prognostic implications. It is an important clinical entity that must be distinguished from classic aortic dissection and rapid expansion or contained rupture of a thoracic aortic aneurysm. Although symptoms of penetrating aortic ulceration may mimic dissection, the characteristic signs of dissection are absent. New imaging modalities have made it possible to establish the diagnosis of penetrating aortic ulceration with a high degree of accuracy and to tailor management according to the presence of complications. Physicians should be aware of the possibility of atherosclerotic aortic ulceration, particularly in elderly patients with systemic atherosclerosis and hypertension who have sudden onset of chest or back pain.