Purpose: To describe a case of penetrating atherosclerotic ulcer of the aorta with a review of its natural history, diagnosis and management. Case Report: An elderly patient with a history of hypertension presented to the emergency room with the sudden onset of severe chest pain radiating to the back. The electrocardiogram showed left ventricular hypertrophy; the chest radiograph revealed mediastinal widening. Computed tomography was suspicious for a mediastinal hematoma without aortic dissection. Transesophageal echocardiography was also negative for dissection. An aortogram revealed a penetrating atherosclerotic ulcer of the descending thoracic aorta. The patient underwent successful resection and repair of the lesion. Conclusions: Penetrating atherosclerotic ulcer of the aorta is a potentially lethal lesion that must be promptly diagnosed and treated.