A cumulative dose-response curve for metocurine based on body weight was determined in 30 infants and children during halothane (1.2 per cent inspired), nitrous oxide and oxygen (60/40 per cent) anesthesia. The mean and range of twitch depression and time for recovery from maximal neuromuscular blockade were not significantly different over an age range from newborn to 7 years. Metocurine is twice as potent as d-tubocurarine in children, and their requirement is more than that for adults. The rate of recovery from metocurine in children was the same as that from d-tubocurarine. In another 30 children, use of metocurine at a large dose (0.5 mg/kg) for endotracheal intubation caused no significant change in blood pressure or pulse rate. Cardiac arrhythmias were not seen.