Bronchopleural fistula developed in 28 (12.5%) of 225 pneumonectomies performed for pulmonary carcinoma of non-small cell types during a 10-year period. The incidence of fistula apparently decreased significantly when chromic catgut was replaced by Dexon for closure of the bronchial stump. The fistula presented as an emergency in nine cases and was subacute in 19. The overall mortality from bronchopleural fistula was 28.6%. Conservative treatment, i.e. bronchoscopic application of silver nitrate to destroy the epithelium in the bronchial stump and induce granulation, achieved closure of fistula in all the surviving patients. In the seven patients with sterile pleural cavity the pleura was not drained. The results justified our principle of conservative management when a bronchopleural fistula does not present as an emergency. In emergency situations, however, or if the pleural fluid is purulent, pleural drainage should be instituted.