OBJECTIVE Spinal anesthesia with ropivacaine has been proven safe both in experimental and clinical studies. On the other hand, ropivacaine is approximately half as potent as bupivacaine in spinal anesthesia when both drugs are used in hyperbaric solutions. This study aimed at comparing clinical spinal block features obtained with hyperbaric ropivacaine or bupivacaine in equipotent doses. METHODS Twenty ASA I or II patients, aged 20 to 60 years, scheduled for elective surgeries of lower limbs, perineum and inguinal hernioplasty, were randomly allocated into two groups . Group R (n = 10) were given 4 ml 0.5% hyperbaric ropivacaine and Group B (n = 10) were given 2 ml of 0.5% hyperbaric bupivacaine intratecally. Puncture was performed with a 25G needle in the sitting position. Monitoring consisted of SBP, DBP, MBP, HR, ECG and SpO2. Sensory and motor block onset and recovery times, hemodynamic and respiratory changes, and the incidence of adverse effects were recorded. RESULTS There were no differences between groups in demographics data, sensory block onset (174.4 +/- 75.9 vs. 191 +/- 51.7 s), motor block onset (373.6 +/- 214.6 vs. 240 +/- 60 s), upper level of sensory block T8 - T10 (90% of group R patients vs. 70% of group B), motor block grade 3 (50% of group R patients vs. 30% of group B), time to total sensory block recovery (178.5 +/- 65.2 vs. 181 +/- 26.9 minutes), time to total motor block recovery (192 +/- 50.7 vs. 162.5 +/- 37.8 minutes), and time for first spontaneous pain complaint (183.9 +/- 37.1 vs. 206.5 +/- 46.6 minutes). CONCLUSIONS No differences in spinal block clinical features were observed between hyperbaric 0.5% ropivacaine and 0.5% bupivacaine, when administered in equipotent doses. Data seem to confirm previous observations that in these conditions, ropivacaines potency is approximately half bupivacaines potency.