Cerebral vasospasm following aneurysmal subarachnoid hemorrhage is one of the most important causes of cerebral ischemia. Hypervolemic hypertension and hemodilution have been reported to be an effective method for prevention and treatment for cerebral ischemia secondary to cerebral vasospasm.We compared the volume expanding effects between normal saline(20 cases), 10% pentastarch(20 cases) and dextran(20 cases) after clipping of cerebral aneurysm in the patients with subarachnoid hemorrhage and the incidence of vasospasm by transcranial doppler(TCD) postoperatively. The results were as follows ;1) The total amount of infused volume in pentastarch and dextran group were 310±46ml, 438 ±262ml respectively,and were significantly smaller than normal saline group, 1078±187ml.(p<0.05) 2) Plasma osmolality was increased by 10 mOsm/kg in pentastarch group, but statistically insignificant. 3) Hematocrit value was decreased significantly in pentastarch and dextran group from 34.9±1.03%, 34.8±1,4% to 31.6±1.38%, 31.9±0.9% respectively.(p<0.05) 4) Cases over 80cm/sec by TCD were 3 in normal saline, 2 in pentastarch, and 2 in dextran group. We conclude that 10% pentastareh could be used as an effective blood volume expander after cerebral aneurysm clipping.