Background: Ropivacaine is an amide local anesthetic structurally related to bupivacaine. A randomized, double-blind study was performed to compare the clinical effectiveness of ropivacaine and bupivacaine in patients undergoing lower-extremity surgery. Methods: Forty-nine patients (ASA 1-2) were randomized to receive 15 ml of 0.5% ropivacaine or bupivacaine. Twenty patients received 15 ml of ropivacaine and 20 patients received 15 ml of bupivacaine at the L3,4 or L4,5 inter-space. Parameters measured were the onset time, duration and spread of sensory block, the onset time, duration and degree of motor block, the quality of anesthesia and the heart rate and blood pressure profile during the block onset. Results: Demographic characteristics were similar among the groups. Seven patients were excluded from the study due to technical failure of the block, two patients were excluded due to insufficient data. The onset and duration of analgesia at T10 dermatome (mean±SD) was 18.9±7.0 minutes and 187.5±34.6 minutes respectively for ropivacaine, and was 15.2±8.8 minutes and 187.8±40.0 minutes respectively for bupivacaine. Maximum block height (mean±SD) was T6.5±2.0 for ropivacaine and T6.4±2.0 for bupivacaine. The incidence of complete motor block (Bromage scale 3) was low in the ropivacaine group, being 3/20 for ropivacaine and 12/20 for bupivacaine. Conclusions: The sensory blockade profile of ropivacaine, administered epidurally, is similar to that obtained with an equal dose of bupivacaine. However motor blockade with ropivacaine is less intense, less frequent, and of shorter duration than with bupivacaine. (Korean J Anesthesiol 2001; 41: 434-438)