To compare the clinical efficacy of hyperbaric 0.5% ropivacaine and 0.5% bupivacaine in subarachnoid blockade for ambulatory surgery.Randomized double-blind study of 90 patients undergoing lower abdominal surgery. Subarachnoid blockade was achieved with 0.5% ropivacaine (12.5 mg) or 0.5% bupivacaine (12.5 mg) in 10% glucose. We recorded age, sex, weight, latency, extension of motor and sensory blocks, duration of surgery, side effects and quality as perceived by the surgeon and the patient.The two groups were similar with respect to latency time and extension of sensory block. Durations of motor (68.9 +/- 22.9 min) and sensory (127.0 +/- 24.3 min) blocks were significantly shorter with ropivacaine than with bupivacaine (133.3 +/- 29.4 and 174.9 +/- 25.5 min, respectively). Patients in the ropivacaine group also experienced a less intense motor block (Bromage 1, 11.1% vs. 93.3%) and fewer episodes of hypotension 0% vs. 17.7%) or bradycardia (4.4% vs. 8.8%) than those in the bupivacaine group. No neurotoxic effects or instances of postdural puncture headache were recorded.Hyperbaric 0.5% ropivacaine offers certain advantages over hyperbaric 0.5% bupivacaine for subarachnoid block in outpatient surgery. Duration and intensity of the sensory-motor blockade is less with ropivacaine and fewer cardiovascular side effects develop.