Fourteen patients suspected of having dissection of the thoracic aorta, 2 with possible extensions into the abdomen of previously diagnosed dissection of the thoracic aorta and 1 patient who had undergone surgical repair of an aortic dissection, were examined by CT (computed tomography). Findings included localized increase of the aortic caliber, displaced intimal calcifications, intimal flaps and false channels. These findings were confirmed by angiography or at necropsy. Two patients in whom CT showed no abnormalities had a favorable outcome. CT evidently is the examination of choice in removing doubt from the clinical diagnosis of aortic dissection.