How to optimize cerebral perfusion pressure and flow during selective extracorporeal circulation is a crucial problem for cerebral protection in surgical repair of aortic arch aneurysm. Among 47 cases of aortic arch replacement between 1980 and 1992, extracorporeal circulation (ECC) for the first 17 cases [group-1] were hypothermic ECC with selective cerebral perfusion (SCP) and 8 cases [group-2] with hypothermic ECC with hypothermic cardiac arrest. For the latest 16 cases [group-3] we introduced continuous O2 saturation monitoring by oximetry catheter placed in internal jugular bulb (SIJVO2) and maintained SIJVO2 value above 90% to effectively adjust pump flow to optimize cerebral perfusion pressure and flow for cerebral protection. We have retrospectively compared the effectiveness of SIJVO2 monitoring among these three groups. The mortality was 35% (6 cases: group-1), 37% (3 cases: group-2) and 6% (1 case: group-3) respectively. Cerebral dysfunction which were diagnosed in immediate postoperative period were 23% (4 cases: group-1), 0% (0 case: group-2) and 6% (1 case: group-3) respectively. We conclude continuous monitoring of SIJVO2 during selective ECC in aortic arch replacement is useful to optimize cerebral perfusion pressure and flow thereby reducing postoperative cerebral damage by selective ECC.