Background: ERCP requires patient cooperation and often prolonged sedation. In different areas of anesthetic practice, patient-controlled sedation with a target-controlled infusion (TCI) of propofol provides effective sedation. The aim of this study was to assess the safety and efficacy of the same system in patients undergoing ERCP. Methods: Twenty patients used the TCI system. Patients received oxygen at 2 L/min via nasal cannulae. By using pharmacokinetic TCI software modeling, an initial propofol target blood concentration (Ct) of 1.0 μg/mL was supplemented on patient demand with a handset that, when pressed twice within 1 second, increased the Ct of propofol by 0.2 μg/mL. The maximum permissible target concentration was set at 3.0 μg/mL to prevent oversedation. Results: Sixteen patients used the system successfully throughout the procedure. The Ct propofol ranged from 1.2 to 2.6 μg/mL, and the number of successful handset activations (after commencement of the ERCP) ranged from 0 to 3. In 3 patients, the ceiling Ct propofol was attained without adequate sedation and the system was manually overridden. The system failed in 1 case because of patient confusion. There were no episodes of hemodynamic instability, airway obstruction, or significant oxygen desaturation. Endoscopist and patient satisfaction were high. Four patients were oversedated according to our criteria at the end of the procedure, but all were awake within 5 minutes of arrival in the recovery area. Conclusions: Patient-maintained sedation with TCI propofol was safe and fully effective in 16 patients. Ease of endoscopy was rated high by the endoscopists, and all patients were well satisfied with their sedation. Adjustments to the software programming are being evaluated to increase the safety profile to avoid oversedation. (Gastrointest Endosc 2001;54:14-7.)