Vecuronium's short half-life and minimal cardiopulmonary side-effects make it a suitable drug for continuous infusion. Vecuronium is used frequently in critically ill patients to increase their total compliance and to minimize the adverse effects of mechanical ventilation. This crossover, prospective study evaluates the use of vecuronium by continuous infusion vs. hourly boluses. Patients were assigned randomly to either method; 12 h later each group was transferred to the other method. Neuromuscular blockade (NMB) was followed with the Train-of-Four method. Cardiopulmonary variables were followed hourly. The total dosage/kg body weight was calculated for each method. Six patients were started with continuous drip and the other six with hourly boluses. There were no significant differences in the cardiopulmonary variables through the two periods, although statistically there was a significant difference in the total dosage/kg body weight required for each method. The mean of total vecuronium used in the drip was 0.79 mg/kg.12 h (range 0.1 to 1.8). The mean of the hourly boluses was 1.34 mg/kg.12 h (range 1.0 to 2.55). Patients on continuous infusion required less vecuronium to maintain a similar NMB (p less than .01).