A prospective study of 4,595 bronchoscopic procedures performed over four years (1975 to 1978) on 2,143 patients with various bronchopulmonary diseases is described. Of the 4,595 procedures, 1,146 were performed with a flexible fiberoptic bronchoscope (Olympus BF-5B2 or BF-B2) under topical anesthesia with tetracaine and procaine, and 3,449 procedures were performed with a rigid bronchoscope under general intravenous anesthesia with hexobarbital (Evipan) using a modified Sanders' technique to ventilate the patients. Complications occurred in 235 procedures (5.1 percent). Major complications that threatened the patient's life and required intensive medical treatment, surgical intervention, or resuscitative measures occurred in 51 procedures (1.1 percent); deaths occurred after 6 procedures (0.1 percent). A comparison of the complications of rigid bronchoscopy and flexible fiberoptic bronchoscopy revealed significantly higher rates of complications of fiberoptic bronchoscopy attributable to toxic effects of tetracaine and of complications of rigid bronchoscopy associated with insufficient general anesthesia. With rigid bronchoscopy, the number of major complications induced by diagnostic manipulations through the bronchoscope and the total number of major complications were significantly higher than with flexible fiberoptic bronchoscopy.