The neuromuscular effects of pancuronium were studied in 65 patients anesthetized with nitrous oxide supplemented by thiopental and/or meperidine. There was a marked variation among patients in their responses to pancuronium. A dose of 0.02 mg/kg depressed twitch height 44 per cent. Recovery to 90 per cent of control twitch height took 16 minutes. With repeated doses a cumulative effect was observed. A dose of 0.04 mg/kg produced an 88 per cent block. Twitch height recovered to 90 per cent of control in 58 minutes. After a dose of 0.08 mg/kg the twitch response was markedly depressed (>98 per cent) or abolished, and the trachea could be intubated with ease. Recoveries to 10 and 25 per cent of control took 65 and 86 minutes, respectively. During a partial block, tetanus was usually poorly sustained and posttetanic facilitation was observed.