STUDY OBJECTIVE Bronchoscopic technique is not standardized. Controversies exist with regard to premedication with sedatives before the test. To evaluate safety and efficacy of conscious sedation, we studied 100 randomized patients undergoing diagnostic bronchoscopy; patients received premedication with lidocaine spray and atropine sulfate i.m. (nonsedation group; 50 patients) or lidocaine spray, atropine i.m. and diazepam i.v. (sedation group; 50 patients). METHODS AND RESULTS Monitoring during flexible fiberoptic bronchoscopy included continuous ECG and pulse oximetry. The procedure could not be completed in six patients. None received premedication with diazepam; among the patients who ended the examination, tolerance to the examination (visual analogue scale, 0 to 100; 0 = excellent; 100 = unbearable) was better in the sedation group. Low anxiety, male sex, but not age were also associated with improved patient tolerance to the test. Oxygen desaturation occurred in 17% of patients, and it was not more frequent after diazepam treatment. CONCLUSIONS In our study, sedation had a beneficial effect on patient tolerance and rarely induced significant alterations in cardiorespiratory monitoring parameters.