A 33-year-old male was admitted to our hospital because of mediastinal bleeding by the traffic accident. He was in shock state. Chest roentgenogram showed widening of the upper mediastium, massive pleural effusion and deviation trachea to right. Chest CT scan showed left hemothorax and deviated mediastinum to right. Immediately after the end of the CT scan, the pulse of bilateral femoral artery was not palpable. Therefore, we started cardiac massage and carried to the operation room in a hurry. Under cardiac massage, median sternotomy was made. But, there were no abnormal findings in the ascending aorta and arch. Under ECC, left anterolateral incision was added. We found that the transection of the descending thoracic aorta was transversely without preservation of the adventitia and it reached a round of the aorta. Five cm of the descending aorta from just distal to the left subclavian artery was replaced with 22 mm Hemashield graft under the separate perfusion of upper and lower body and circulatory arrest. Postoperative course was stable and the patient was healthy at present.