Sixty children aged one to 12 years requiring anaesthesia including a muscle relaxant were assessed for their nutritional status based on simple anthropometric and biochemical parameters. They were allocated to one of four groups: normal nutrition, mild, moderate or severe malnutrition. The neuromuscular effects of vecuronium bromide 0.1 mg/kg were studied by recording evoked responses to train of four (TOF) nerve stimulation using an accelerograph. In the above nutritional groups, time to onset of 25% depression of T1 was 0.8, 1.4, 1.3 and 2.1 minutes respectively. Maximal depression of TOF response was seen at 2.2, 3.2, 3.7 and 8.4 minutes. The duration of action of the initial dose was 26.5, 24.0, 17.7 and 13.3 minutes and the mean duration of action of top-up doses was 16.2, 14.9, 11.2 and 8.9 minutes respectively. Reversal time with neostigmine 0.05 mg/kg was not significantly different in the four groups. These results demonstrate a statistically significant delay in onset and shortening of the duration of action of vecuronium in the undernourished groups compared with the normal nutrition group when vecuronium is administered to children on a milligram per kilogram basis.