Chronic traumatic aneurysm of the thoracic aorta is an unusual occurrence. Previously, arteriography was performed on all patients seen in our institution with this entity to allow confirmation of the diagnosis and anatomic delineation for operation. A case of chronic traumatic aneurysm of the distal descending aorta discovered on a routine chest roentgenogram and evaluated with chest computed tomographic scanning with three-dimensional reconstruction is presented. It is our belief that not all thoracic aneurysms require arteriography, and improved methods of computed tomographic scanning allow adequate diagnosis and anatomic delineation with decreased morbidity and cost.