Surgical treatment of aneurysm or dissection involving the ascending aorta and aortic arch still poses one of the most complicated technical and tactical challenges in surgery. The use of total circulatory arrest[TCA] with profound hypothermia in the surgical treatment of aneurysmal dissection involving the ascending aorta and aortic arch has been reported as popular surgical methods. However, the safe period of prolonged circulatory arrest with hypothermia remains controversial and ischemic damage to the central nervous system and uncontrollable perioperative bleeding have been the major problem. We have found profound hypothermic circulatory arrest with retrograde cerebral perfusion via the superior vena cava to achieve cerebral protection. We experiment the aortic anastomosis in 7 adult mongrel dogs, using profound hypothermic circulatory arrest with continuous retrograde cerebral perfusion[RGCP] via superior vena cava. We also studied the extent of cerebral protection using above surgical methods, by gas analysis of retrograde cerebral perfusion blood and returned blood of aortic arch, preoperative, intraoperative and postoperative electroencephalography and microscopic findings of brain tissue. The results were as follows: 1. The cooling time ranged from 15 minutes to 24 minutes[19.71$pm$ 3.20 minutes] ; Aorta cross clamp time ranged from 70 minutes to 89 minutes[79.86 $pm$ 7.54 minutes] ; Rewarming time ranged from 35 minutes to 47 minutes[42.86$pm$ 4.30 minutes] ; The extracorporeal circulation time ranged from 118 minutes to 140 minutes[128.43$pm$ 8.98 minutes] [Table 2]. 2. The oxygen content in the oxygenated blood after RGCP was 12.66$pm$ 1.25 ml/dl. At 5 minutes after the initiation of RGCP, the oxygen content of returnedlood was 7.58$pm$ 0.21 ml/dl, and at 15 minutes 7.35$pm$ 0.17 ml/dl, at 30 minutes 7.20$pm$ 0.19 ml/dl, at 60 minutes 6.63$pm$ 0.14 ml/dl [Table 3]. 3. Intraoperative electroencephalographic finding revealed low amplitude potential during hypothermia, and no electrical impulse throughout the period of circulatory arrest and RGCP. Electrical activity appeared after reperfusion, and the electroencephalographic reading also recovered rapidly as body temperature returned to normal [Fig. 2]. 4. The microscopic finding of brain tissue showed widening of the interfibrillar spaces. But there was no evidence of tissue necrosis or hemorrhage [Fig. 3]. We concluded the retrograde cerebral perfusion during hypothermic circulatory arrest is a simplified technique that may have a excellent brain protection.