Autotransfusion has been known to have many benefits in patients who might have anticipated or unanticipated hemorrhage during elective or emergency surgical procedures. Twenty-nine patients with intracranial aneurysms with subarachnoid hemorrhage were enrolled in this study. Sixteen aneurismal patients were randomly selected for autotransfusion group, whose hematocrit value ranged between 21 to 39% after aspiration of mean arterial blood volume of 850 ml. For auto-transfusion, and 13 patients were given only homologous banked glood during surgical operation as control group. During surgical operation for direct clipping on aneurysmal neck in autotransfusion group, autotransfusion was applied by the method of perioperative blood collection and acute hemodilution of 30% hematocrit value. In 13 control aneurysmal patients who needed homologous banked blood during surgical operation to maintain normal blood pressure and intravascular blood volume, average mean volume of banked blood reguired was 1104 ml. In 16 aneurysmal autotransfusion group, it was only 438 ml of banked blood, and furthermore in 4 patients among them, homologous banked blood was not needed at all.