BACKGROUND: Tetracaine has been the most commonly used long-acting spinal anesthetic agent. Recently, hyperbaric bupivacaine was introduced to be useful agent, and has been reported to produce the better quality of anesthesia. The aim of the present investigation was to compare the anesthetic effects of 0.5% hyperbaric bupivacaine and 0.5% hyperbaric tetracaine spinal anesthesia. METHODS: 40 ASA Class I patients undergoing lower extremity operation were randomly distributed to two groups. Group A (n=20) received 15mg, 0.5% bupivacaine in 8% glucose, while Group B (n=20) received 15mg, 0.5% tetracaine in 10% glucose in the lateral decubitus position (L3,4 interspace). We evaluated the sensory and motor blockade, cardiovascular effects and the incidence of tourniquet pain. RESULTS: The mean maximum cephalad spread of analgesia was higher in bupivacaine group (T5) than in tetracaine group (T6) and the spread time was more rapid in bupivacaine group (13.1 +/- 3.3min.) than in tetracaine group (15.8 +/- 4.3min.), but there were no statistical significances. Tetracaine group was earlier onset of motor block and the duration of complete motor block in tetracaine group was significantly longer than in bupivacaine group. The mean decrease in systolic and diastolic blood pressure was 10% to 25% in both groups and more marked in tetracaine group. The incidence of tourniquet pain was greater in tetracaine group than in bupivacaine group. CONCLUSIONS: The quality of anesthesia obtained with bupivacaine may be superior to that produced by tetracaine. We concluded that 0.5% hyperbaric bupivacaine was suitable for short orthopedic or lower abdominal surgery because of less incidence of hypotension, shorter duration of motor block and lower incidence of tourniquet pain.