The effect, duration and complications of subarachnoid anesthesia with hyperbaric bupivacaine solution, adjusted at a gravity of 1.044 and 1.033 by adding glucose, were compared with those of isobaric 0.5% bupivacaine anesthesia. Thirty patients undergoing surgical operations on lower abdomen or lower extremities were divided into three groups and given 2.0 to 4.0 ml of bupivacaine at L3-4 according to the body height. The upper margin of analgesic zone at 15min and 60min after the subarachnoid injection of bupivacaine was higher in the hyperbaric groups, but it receded thereafter and significant differences were found at 120min compared with the isobaric group. Hypotension occurred less frequently in the hyperbaric groups. The short duration of analgesia in the hyperbaric groups may be attributable to the lower concentrations of bupivacaine, 0.40 and 0.45%, but the low frequency of hypotension might be due to the younger mean ages of these two groups. No notable complications were found in any group. Bupivacaine solution of 0.5% with a higher gravity is desired in the market.