In the early period up to 1986, our treatment of acute type III dissection was anti-hypertension drug therapy as a rule, and Collins operations were performed in two cases of progressive hemothorax. Among 21 patients receiving medical therapy, five died of rupture, and three operated cases died of multiple organ ischemia, and then the hospital mortality was 40%. Since 1987, we have selected hypotensive treatment of strictly maintaining blood pressure less than 120mmHg for the completely thrombosed type of the dissected lumen, and the emergency operation of ringed intraluminal graft insertion (RIG operation) for the blood-flow type and aneurysm formation type of the dissected lumen, diagnosed by the emergency cine-angiography. As the result, among 51 cases having hypotensive therapy, one died of respiratory failure. In the 23 operated cases, in which RIG operation and/or arterial reconstruction was performed, four died of multiple organ ischemia. The hospital mortality was 8%, which was significantly improved compared with that of the early period.