The use of neuromuscular blocking agents, particularly pancuronium, in patients receiving mechanical ventilation has been reported to cause prolonged paralysis and atrophy. We describe two mechanically ventilated patients with asthma who developed prolonged muscular weakness and atrophy after receiving the shorter-acting agent vecuronium. These cases illustrate the potential of any neuromuscular blocking agent to cause these complications, especially in patients who are immobile, have decreased renal or liver function, or receive concomitant myotoxic agents.