Rheomacrodex-D 10% W/V in dextrose(550ml) was prophylactically infused before anesthesia over 15 to 20 minutes to prevent hypotension during spinal anesthesia in 20 patients undergoing elective Cesarean section. Apgar scores and the incidence and severity of hypotension were compared to results obtained in 20 patients who were given 500 ml of Hartmann's solution. The results were as follows: 1) Mean arterial pressure decreased up to 20 torr from control values in patients hydrated with Hartman's solution and also changed significantly in patients given Rheomacrodex-D(p<0.05). 2) The incidence and severity of hypotension at 10 minutes, and 15 minutes, and 15 minutes after spinal anesthesia(p<0.05) was significantly less in patients given Rheomacrodex-D than in patients hydrated with Harmann's solution. 3) The Apgar scores, both at 1 minute and 5 minutes, were significantly higher(p<0.05, p<0.005) in infants born of mothers given Rheomacrodex-D than in infants whose mothers were given Hartmann's solution. 4) The cases of hypotension defined as a decrease in systolic arterial pressure lower than 100 torr or a decrease in mean arterial pressure to 25% from control values were 12 cases in 20 patients hydrated with Hartmann's solution and 6 cases in 20 patients given Rheomacrodex-D.