Twenty-nine patients who underwent operation at Shinshu University Hospital for the Stanford type A dissecting aneurysm were analysed. The patients were operated on in the acute stage within 2 weeks after onset. In 13 of these 26 acute cases, the graft replacement of the ascending and arch of the aorta was performed (group A). The patients were operated under a separate perfusion to the brain and the distal anastomosis to the proximal portion of the descending aorta was performed using the method of open distal anastomosis. In other 13 cases, the graft replacement of the ascending aorta was performed (group B). Operative mortality rate was 19% in this series (group A: 23%, group B: 15%). There was no significant difference in their operative mortality of acute stage. And there was also no significant difference in their post operative course of acute stage operations. We concluded that the graft replacement of the ascending and arch of the aorta was better than the graft replacement of the ascending aorta alone for the patients with Stanford type A acute aortic dissection.