The neuromuscular blocking effects and recovery times following two doses of succinylcholine on a weight basis were evaluated in 16 infants and 16 children. Infants had less profound neuromuscular blockade than children at both 0.5 and 1.0 mg/kg doses. Succinylcholine, 1 mg/kg, in infants produced blockade equal to that produced by 0.5 mg/kg in children; at these equipotent doses there was no statistically significant difference between the times to recover to 10 and 90 per cent neuromuscular transmission in the two groups. However, the rate of recovery from 50 per cent neuromuscular transmission to 90 per cent neuromuscular transmission was 69.1 per cent/min in children, as opposed to 46.4 per cent/min in infants. When dosage was calculated on a surface area basis, there was a linear relationship for infants and children as a single group between the log dose and the times to recover to 50 and 90 per cent neuromuscular transmission. Similarly, there was a linear relationship between the log dose (mg/m2) and the maximum intensity of neuromuscular blockade.