BACKGROUND: Patients who are scheduled for upper extremity surgery under brachial plexus block (BPB) prefer to have no memory of the surgical procedure and some form of sedation is therefore necessary. Because of this we have tried to find an adequate infusion method for propofol that would supply better sedation and less complications. METHODS: We divided 60 patients who were scheduled for upper extremity surgery under BPB into four groups according to loading dose and following continuous infusion rate of propofol (Group 1: 0.2 mg/kg, 8 microgram/kg/min, group 2: 0.4 mg/kg, 16 microgram/kg/min, group 3: 0.6 mg/kg, 33 microgram/kg/min, group 4: 0.8 mg/kg, 50 microgram/kg/min.). We evaluated the degree of sedation, amnesia, recovery, changes of blood pressure, heart rate, and respiratory effect of each group. RESULTS: According to the sedation score, groups 3 and 4 were sedated better than groups 1, 2 (P< 0.05). But the mean arterial pressure (MAP), heart rate and respiration were more depressed and recovery time prolonged in the higher dosage groups (P< 0.05). Three patients among group 4 developed severe respiratory depression, at which time infusion of propofol was stopped. CONCLUSIONS: The ideal infusion method of propofol for effective sedation was 0.4 0.8 mg/kg of loading dosage, followed by 16 50 microgram/kg/min of continuous infusion dosage. But the more dosages of propofol that were administered, the more complications appeared, so we must use care in administering propofol as a sedation adjuvant to BPB.