During a three years period, qq patients with clinically suspected aortic dissectino were diagnosed by CT as the primary mode of investigation. Chest roentgenography was performed in all 11 patients and ultrasonography was performed in 2 patients. None of them pbtained aortography. RESULT : 1. 7 cases were female and 4 male, with a mean age of 65 years. 2. All of them suffered from hypertension. The most consistent clinical symptom was severe tearing chest pain which was radiating to back. ECG revealed the findings of LVH in all 11 cases. 5 cases were expired within 2 weeks and 6 cases treated medically with symptomatic improvement. 3. Chest roentgenography revealed sugestive signs of dissecting aortic aneurysm such as widening of superior mediastinum. shifting of trachoea to the right side, ogliteration of aortic knob, double aortic knob, displacement of intimal calcification and pleural effusion. 4 CT findings proffered us useful informations which were double channel with i timal flap, displacement of intimal calcification, thrombosis, increased diameter of aorta, pleural and pericardial effusion, and narrowness of true lumen. 5. The authors recommend a CT study as the most important preliminary examination in all suspected cases of dissecting aortic aneurysm even though it has some limitations.