Cumulative dose-response curves were constructed for pancuronium, metocurine, d-tubocurarine and gallamine in 56 children anaesthetized with thiopentone, N2O/O2 and narcotic. The dose response curves of the four relaxants did not deviate significantly from parallelism. The effective dose causing 95 per cent depression of the twitch at 0.1 Hz was: pancuronium 0.08 mg X kg-1, metocurine 0.34 mg X kg-1, d-tubocurarine 0.6 mg X kg-1, and gallamine 3.4 mg X kg-1. Thus, pancuronium is 40 times more potent than gallamine, while metocurine and d-tubocurarine are seven and four times more potent than gallamine. The recovery of twitch height from 5-25 per cent of control for pancuronium (15.6 +/- 1.7 min) was significantly faster (p less than 0.01) than metocurine (27.3 +/- 1.9 min), d-tubocurarine (32.2 +/- 4.8 min), or gallamine (30 +/- 3.3 min). Compared to studies in adults, the present data indicate that children have a tendency (statistically not significant) to require more relaxant and recover more quickly than adults.