We were interested in determining the cumulative dose-response relationship of pancuronium in infants and children during nitrous oxide-halothane anaesthesia. Neuromuscular blockade was monitored by recording the electromyographic activity of the adductor pollicis muscle from supramaximal stimulation of the ulnar nerve at 2 Hz for 2 s at 10 s intervals. Forty patients were divided into four equal groups according to age: 3-6 months, 7-12 months, 1 3 4 7 months and 48-83 months. The effective dose, ED50 (mean f SEM), of pancuronium in these age groups was 24 +_ 2,30 k 2,34 +_ 3,29 _t 2 pg-kg-l, respectively; the ED95 (mean k SEM) was 45 k 2,52 f 3,62 f 6,62 f 4 pgkg-', respectively. The ED95 of pancuronium was significantly less (P < 0.05) for infants from 3 to 6 months of age than for children from 13 to 83 months of age. Infants thus appear to be more sensitive than children to the neuromuscular blocking effects of pancuronium during halothane anaesthesia.