OBJECTIVE: This prospective randomized study evaluated the efficacy and patient tolerance of dexmedetomidine compared with midazolam for sedation in postoperative patients undergoing flexible bronchoscopy. METHODS: A total of 198 postoperative patients were randomized to receive dexmedetomidine (n = 99) or midazolam (n = 99) to produce conscious sedation for bronchoscopy. Peripheral oxygen saturation, heart rate and systolic and diastolic arterial pressures were recorded before, during and after the procedure. Patient tolerance was recorded using various visual analogue scales. RESULTS: The mean lowest peripheral oxygen saturation was significantly lower in the midazolam group than in the dexmedetomidine group. Heart rate and systolic arterial pressure were both significantly higher during bronchoscopy in the midazolam group than in the dexmedetomidine group. Bronchoscopy was well tolerated in both groups; there was no betweengroup difference in patient discomfort scores or in the percentage of patients who would accept repeat bronchoscopy. CONCLUSIONS:Compared with midazolam, dexmedetomidine provided better oxygen saturation and was equally well tolerated for conscious sedation in postoperative patients undergoing bronchoscopy.