BACKGROUND: The technique using target-controlled infusion (TCI) with propofol produces safe intraoperative sedation during regional anesthesia with rapid recovery and high patient satisfaction. The objective of this study was to define the blood propofol concentration necessary for conscious sedation in regional anesthesia patients according to age. METHODS: Sixty patients scheduled to undergo regional anesthesia were allocated into one of three groups according to age, such as group 1 (n = 20): 16 24 yr, group 2 (n = 20): 30 39 yr, group 3 (n = 20): 40 55 yr. Thirty minutes after performing regional anesthesia, TCI of propofol started at a target plasma level of 1 microgram/ml adjusted in steps of 0.2 microgram/ml to maintain a sedation level 3 on a 5-point sedation scale. RESULTS: The mean target concentration was 0.9 microgram/ml (group 1), 0.8 microgram/ml (group 2), 0.7 microgram/ml (group 3). The mean propofol consumption was 38.5 microgram/kg/min (group 1), 34.3 microgram/kg/min (group 2), and 30.8 microgram/kg/min (group 3). The recovery time was significantly delayed in group 3 (2.8 min) compared to group 1 (1.5 min) and group 2 (1.8 min). CONCLUSIONS: TCI of propofol within at 0.7 0.9 microgram/ml blood concentration range produces safe intraoperative sedation during regional anesthesia with rapid induction, rapid recovery and high patient satisfaction without severe complications in 16 55 yr old patients.