PURPOSE: To evaluate the radiologic findings of acute intramural hematoma of the aorta, and the clinical follow up thereof. MATERIALS AND METHODS: Among 34 cases confirmed clinically and radiologically as aortic dissection, an analysis was carried out based on 15 cases in which intramural hematoma without false lumen was demonstrated, on initial CT, 12 cases of in which follow up CT was used and five cases involving an aortogram. Elements such as the shape of the thickened aortic wall, ulcer-like intimal defects, and intimal calcification were examined. Changes in these elements were also examined on follow up CT. RESULTS: DeBackey types I and III accounted for one and 14 cases. respectively. Initial precontrast CT demonstrated continuous, crescentic high attenuation areas along the wall of the descending aorta. In postcontrast scans, the crescentic areas were of relatively lower-attenuation and appeared along the aorta wall. Displaced intimal calcifications were seen in nine of fifteen patients. There was no intimal flap on all five aortogram, while aortic wall thickening and atherosclerotic change were demonstrated in four cases and in one case, case, respectively. Focal ulcers were seen in three cases. Ulcer-like intimal defects were demonstrated in a total of eleven cases (eight on CT, two on aortogram, and one on both). In ten of the twelve cases seen on follow up CT, the thickness of the intramural hematoma was seen to be reduced. Among the 15 cases, the operation was performed in two cases, and the remaining 13 received conservative treatment. In ten cases observed for more than twelve months, a recurrence of symptoms did not occur. CONCLUSION: Eccentric aortic wall thickening in patients who complain of acute chest pain is the result of acute aortic dissection with intramural hematoma, or a penetrating atherosclerotic ulcer of the aorta.The latter may be differentiated from the former by the presence of on ulcer-like intimal defect. When both diseases are limited to the descending aorta, conservative treatment may be effective, unless patients experience persistent or recurrent chest pain, or unless intramural hematoma progresses further.