Fifteen patients with chronic bronchitis and airflow obstruction which was not improved by inhalation of isoproterenol (increase in forced expiratory volume in one second [FEV1] less than 15%) received an aerosol of atropine sulfate (0.05 mg/kg of body weight), in order to determine their response to an anticholinergic bronchodilator drug. The improvement over initial values for FEV1 at 15 minutes following inhalation of isoproterenol and at 90 minutes following inhalation of atropine averaged 5.9% and 19.2%, respectively (P < 0.01). Eleven of 15 patients demonstrated a 15% or greater increase in FEV1 following inhalation of atropine, and 6 subjects demonstrated more than 25% improvement. The maximum effect of atropine was observed at or later than 90 minutes following inhalation in 9 of 11 patients who were responsive to atropine. Minimal systemic toxic effects resulted from inhalation of atropine, although dryness of the mouth was frequent. In patients with chronic bronchitis, airflow obstruction resistant to isoproterenol may respond to inhalation of an aerosol of atropine sulfate.