BACKGROUND The aim of this study was to determine the clinical effective dose of rocuronium for tracheal intubation using a lightwand after induction with propofol, alfentanil, and a low concentration of sevoflurane. METHODS Twenty-eight adults scheduled to undergo elective surgery lasting less than one hour were enrolled in this study. All patients received alfentanil (10 microg/kg) and propofol (1.5 mg/kg) for the induction of anesthesia. Tracheal intubation using a lightwand was attempted 3 minutes after administering rocuronium and mask ventilation with 2 vol% of sevoflurane. The initial rocuronium dose was 0.5 mg/kg. The rocuronium dose for consecutive patients, determined by Dixon's up-and-down method, was increased or decreased by 0.05 mg/kg according to the result of the previous patient. The mean arterial pressure and heart rate were recorded before induction, 1 min before intubation, 1 and 2 min after intubation. RESULTS The 50% clinical effective dose (cED(50)) of rocuronium for tracheal intubation using a lightwand was 0.20 +/- 0.05 mg/kg according to Dixon's up and down method. Isotonic regression revealed the cED(50) and cED(95) (95% confidence intervals) to be 0.20 mg/kg (0.10-0.3 mg/kg) and 0.35 mg/kg (0.16-0.49 mg/kg), respectively. CONCLUSIONS The cED(50) and cED(95) of rocuronium for tracheal intubation using the lightwand were 0.20 mg/kg and 0.35 mg/kg, respectively, after induction with alfentanil, propofol, and a low concentration of sevoflurane.