Forty-three ASA physical status I and II patients, scheduled for elective urologic surgery, were randomly entered into a randomized double-blind study using 20 ml bupivacaine 0.75% or 20 ml ropivacaine 0.75%, both with 5 micrograms/ml epinephrine. Two patients were excluded from evaluation of efficacy due to technical failure. After a test dose of 3 ml bupivacaine 0.75% with epinephrine or ropivacaine 0.75% with epinephrine, 17 ml of either solution was given in incremental doses over 4 minutes (4, 4, 4, and 5 ml). Analgesia was satisfactory for surgery in all patients except for one in each group. The onset time of analgesia was short: after administration of ropivacaine and bupivacaine, the T12 dermatome was blocked within 6-8 minutes. Mean maximum upper level of analgesia was similar in the groups--T8 +/- 0.6 and T7 +/- 0.6 (mean +/- SEM)--for ropivacaine and bupivacaine, respectively. Duration of analgesia at the T10 level was 190 +/- 12 minutes in the ropivacaine group and 234 +/- 20 minutes in the bupivacaine group and was significantly shorter for ropivacaine at T10, L2, and S5 segments. Frequency of complete motor block was significantly lower in the ropivacaine group (7/21) than in the bupivacaine group (16/20). No differences were found in onset to various degrees of motor block, however, the duration of degree 1 motor block was significantly shorter in the ropivacaine group. Hypotension and bradycardia requiring treatment were experienced by seven and three patients, respectively, in the bupivacaine group, and by two and one patient, respectively, in the ropivacaine group. No postoperative adverse events related to anesthesia were observed. Ropivacaine 0.75% with epinephrine is an effective long-acting local anesthetic. Duration of sensory block is similar to that of bupivacaine 0.75% with epinephrine; however, the motor block is less profound and of shorter duration.