Authors selected 54 patients in ASA class I, II, aged from 20 to 60 years old undergoiag operations of lower limbs and lower abdomen. In the different dosage of 0.25% hyperbaric bupivacaine, these were divided into 3 groups ; group A(22 patients) using l0 mg(4 ml), group B(17 patients) using 15 mg(6 ml), group C(15 patients) using 20 mg(8ml), which were injected into subarachnoid space. The following results were obtained. I) Maimum level of sensory loss was significantly increased with increase dosage, and the time of onset was significantly faster with decrease dosage. 2) Duratioan of sensory loss was significantly longer with increase dosage. 3) Onset time of motor block was signficantly faster in the group C of Bromages scale degree l, Duration of motor block was signficantly longer with increase dosage. 4) Systolic and diastolic blood pressure were little decreased with increase dosage. No signficant changes were noted in the pulse rate. 5) Post spinal headache developed in 5 patients out of 54 patients(9.3%). In the study of the group C, urinary retention developed in 4 patients out of 15 patients. From above results, we conclude that 0.25% hyperbaric bupivacaine can be used for operations lasting than 1~2 hours of lower limbs and lower abdomen because cardiovascular system is little affected with increase dosage.