Background: There are few controlled studies on balanced propofol sedation (BPS) for therapeutic endoscopy. Objective: To compare the safety and efficacy of BPS (propofol in combination with midazolam and meperidine) with conventional sedation (midazolam and meperidine) in patients undergoing therapeutic endoscopic procedures. Design: Prospective, randomized, single-blinded study. Setting: Tertiary-care referral center. Patients: This study involved 222 consecutive patients undergoing therapeutic EGD or ERCP from July 2009 to March 2010. Intervention: Conventional sedation or BPS by trained registered nurses under endoscopist supervision. Main Outcome Measurements: Rates of sedation-related cardiopulmonary complications and interruption of the procedures, procedure-related times, and assessments of health care providers (endoscopists and sedation nurses) and patients. Results: There were no significant differences between the BPS and conventional groups in the rates of cardiopulmonary complications (8.8% [9/102] vs 5.8% [6/104], respectively) and transient interruption of procedures (2.9% [3/102] vs 0% [0/104], respectively). No patient required assisted ventilation or premature termination of a procedure. BPS provided significantly higher health care provider satisfaction (mean +/- SD 10-cm visual analog scale [VAS] score) compared with conventional sedation (endoscopists: 7.57 +/- 2.61 vs 6.55 +/- 2.99, respectively; P = .011; sedation nurses: 7.86 +/- 2.31 vs 6.67 +/- 2.90, respectively; P = .001). Patient cooperation was significantly better in the BPS group (VAS; endoscopists: 7.24 +/- 2.97 vs 6.27 +/- 3.09, P = .024; sedation nurses: 7.75 +/- 2.30 vs 6.54 +/- 2.99, P = .001). Limitations: Single-center and single-blinded study. Conclusion: Compared with conventional sedation. BPS provides higher health care provider satisfaction, better patient cooperation, and similar adverse event profiles in patients undergoing therapeutic endoscopic procedures. (Gastrointest Endosc 2011;73:206-14.)