Propofol is a new intravenous anesthetic which possesses the rapid induction and recovery of anesthesia. It has been approved to be used in clinical anesthesia and critical care medicine since 1989. From the dose-response study of propofol, we can get the ED50 and induction dose of propofol and compare those with other anesthetics. Sixty young patients, ASA I-II, both sexes, were allocated into six groups of ten patients. All of patients did not receive premedicants. Groups I-VI were given intravenously over 25 sec 1.0 mg/kg, 1.2 mg/kg, 1.4 mg/kg, 1.6 mg/kg, 1.8 mg/kg and 2.0 mg/kg, respectively. Blood pressure and heart rate were monitored and recorded before and 1 min, 3 min, 5 min after the injection of propofol. Induction of anesthesia by propofol is considered to be successful as a patient closes his eyes and does not response to simple command. As a patient obeys the order to open his eyes, he is judged to emerge from anesthesia. Induction and recovery times were recorded in each successfully-induced patient. Data were analyzed using Litchfield and Wilcoxon, and Student's t tests. The ED50 of propofol was found to be 1.46 mg/kg (95% confidence interval: 1.35 mg/kg to 1.58 mg/kg). Induction and recovery times at 1.0 mg/kg, 1.2 mg/kg, 1.4 mg/kg, 1.6 mg/kg, 1.8 mg/kg and 2.0 mg/kg were 40 sec and 5.6 min, 38 sec and 6.0 min, 38 sec and 6.2 min, 36.8 sec and 6.7 min, 36.3 sec and 7.2 min, 35.5 sec and 7.2 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)