Neuromuscular blockade by vecuronium infusion is described in 13 patients requiring ventilation in an ICU for periods of 15 to 68 h. A loading dose of vecuronium (0.1 mg/kg) was given, followed by continuous infusion adjusted to maintain approximately 90% block as assessed by the presence of one response to a Train-of-Four stimulation. The average infusion rate was 0.103 mg/kg.h. The average time to complete recovery of myoneural function, as assessed by an obviously sustained response to tetanic stimulation, after the termination of the vecuronium infusion was 28 min. There were no adverse cardiovascular or toxic effects noted as a result of vecuronium administration. Vecuronium administered by infusion produced satisfactory neuromuscular relaxation in patients requiring ventilation in the ICU.