Volatile anesthetics have long been known to interfere with the action of neuromuscular blocking agents. This study was to determine the effect of 1% sevoflurane on the duration of an intubation dose (0.1% mg/kg-1) of vecuronium during N2O-fentanyl anesthesia. Thirty ASA class I-II female patients were randomly allocated to receive either droperidol (group 1) or 1% sevoflurane (group 2). Neuromuscular function was monitored by means of the Accelograph TM. The duration of vecuronium was 44.86(8.57 minutes in group 1 and 39.58(3.95 minutes in group 2. Group 2 tended to have a shorter duration than group 1 (p =0.03). The finding does not agree with previous studies which reported the potentiating effect of sevofluranes on the action of neuromuscular blocking agents. This contradictory result may be due to the initial stimulatory effect of low concentration (1%) sevoflurane on the muscle cells.