Pulmonary function is reportedly impaired by fiberoptic bronchoscopy. We investigated the effect of two anticholinergic agents, intramuscular atropine and inhaled ipratropium bromide, on bronchoconstriction in 29 patients who were undergoing diagnostic bronchoscopy. The patients were divided into three groups; the first received 0.5 mg of atropine intramuscularly; the second took four puffs of 0.02 mg ipratropium bromide aerosolized by a metered-dose inhaler, and the third inhaled four puffs of a placebo. Fifteen minutes later a standardized topical anesthetic, lidocaine, was administered, and a bronchoscopic examination was performed. Pulmonary function was measured before and 15 minutes after each step. Pulmonary function was not affected by the treatment with anticholinergics or the placebo. In the placebo and the atropine groups, the topical anesthesia produced significant reductions in forced expiratory volume in 1 second (FEV1) and peak expiratory flow rate (PEFR); further reductions in these values were observed after bronchoscopy. In the group treated with ipratropium bromide there were no significant changes in FEV1 and PEFR after topical anesthesia. Bronchoscopy induced significant reductions in FEV1 and PEFR, but the changes were significantly smaller than those seen in the placebo and atropine groups. The results suggest that the deleterious effect of bronchoscopy on pulmonary function is due to topical lidocaine anesthesia and to the bronchoscopic examination itself. Inhaled ipratropium bromide protects against these deleterious effects, whereas intramuscular atropine does not.