The mechanisms of airflow limitation in bullous lung disease were examined by plotting maximal expiratory airflow and airway resistance against lung elastic recoil pressure. in 5 patients who had evidence of isolated bullae, the abnormalities in airway resistance and in expiratory airflow could be accounted for by loss of lung elastic recoil. in 2 additional patients, the abnormalities could not be accounted for completely by loss of lung elastic recoil, suggesting that intrinsic airway disease was also present; these 2 patients had clinically evident chronic bronchitis. in 2 of the patients, tantalum bronchography confirmed the physiologic studies. Postoperative studies in the one patient who underwent bullectomy demonstrated maintained physiologic improvement in lung elastic recoil and in airway resistance.