Midazolam, a water soluble benzodiazepine, was compared with diazepam as a sedation for spinal anesthesia. Forthy healthy patients were allocated at random to receive midazolam 0.1mg/kg or diazepam 0.2mg/kg at 15 min after tetracaine inction for spinal anesthesia and increments of half of the initial dose every 2 min to induce sleep. Mean dose of midazolam 8.5 mg and diazepam 17.1 mg were injected for sedation throughout surgery. There was no difference concerning sedation level during surgery and speed of recovery. With the same degree of sedation, midazolam produced a higher frequency of anterograde amnesia(70% vs. 30%). Uenous tolerance was better for midazolam. Neither drug caused obstruction of airway nor significant cardiovascular change. Higher degree of amnesia and venous tolerance with midazolam may be advantages of sedation for spinal anesthesia.