BACKGROUND: When given as an intravenous bolus for induction of anesthesia, propofol with fentanyl can induce moderate to severe preintubation hypotension and bradycardia. The goal of this study was to evaluate the effect of ephedrine to prevent hypotension and bradycardia and to compare methods of ephedrine administration. METHODS: Forty five patients of ASA physical status 1 or 2 were randomly assigned to one of three groups of 15 patients each to receive either normal saline (G I), ephedrine 0.2 mg/kg IV 2 min before the injection of propofol (G II), or propofol mixed with ephedrine 0.2 mg/kg (G III). Each group first received fentanyl 2ng/kg and 2 min later received propofol 2 mg/kg as an intravenous bolus to induce anesthesia. Anesthesia was maintained by a continuous infusion of propofol 20 mg for 8 min until intubation. The changes of systolic and diastolic arterial pressure, and heart rate were measured before induction (0 min), 2, 4, 6, and 8 min after induction, and post intubation (10 min). RESULTS: The decrease of systolic and diastolic pressure in G II and G III were attenuated compared with those of the control group. The difference was significant at 2, 4, and 6 min in G II, and at 2 and 4 min in G III (P < 0.05). The decrease of heart rate in G II (8 min) and G III (6 and 8 min) were also less marked than those in G I (P < 0.05). The increase of heart rate of post intubation (10 min) was greater in G II and G III than in G I (P < 0.05). There was no statistical difference among the groups in the increase of systolic and diastolic pressures after intubation. CONCLUSIONS: Prophylactic ephedrine significantly attenuated the decrease in blood pressure and heart rate during induction of anesthesia with fentanyl and propofol. There was no statistical difference between the ephedrine groups.