The use of an infusion of vecuronium is described in seven patients with renal and respiratory failure in an intensive therapy unit. Neuromuscular function was monitored throughout using the train-of-four twitch technique. A bolus dose of vecuronium (0.1 mg/kg) was given, followed immediately by a continuous infusion (0.05 mg/kg/hour). The infusion rate was adjusted until the first twitch of the train was below 20% of control and then run at a constant rate. There was a marked variation in the dose of vecuronium administered (0.01-0.065 mg/kg/hour [corrected]). Two patients, who appeared to be most sensitive to the drug, were both receiving metronidazole. Recovery of neuromuscular function was extremely prolonged and widely variable (6-37 hours) on stopping the infusion. No adverse cardiovascular effects or evidence of histamine release were seen as a result of administration of the drug. Vecuronium is probably more suitable for administration in bolus doses rather than by infusion in patients with renal and respiratory failure.