The effect of nasal continuous positive airway pressure (CPAP) was assessed in three patients with tracheobronchomalacia (TBM) who failed conventional medical management. Using physiologic measures of airflow and fiberoptic bronchoscopy, we evaluated expiratory airflow and airway collapse during the acute administration of nasal CPAP. FVC increased and dynamic airway collapse [slow vital capacity minus forced vital capacity (SVC--FVC)] decreased with increasing levels of CPAP. Notching associated with airway collapse was observed in the baseline spirograms of all three patients, and it disappeared with the addition of nasal CPAP. Fiberoptic bronchoscopy confirmed the severity of TBM in each patient and documented an acute improvement in expiratory airway collapse with the addition of nasal CPAP. Intermittent nasal CPAP was then added to the patients' treatment regimens, improving the course of their disease. Specific treatment outcomes varied from patient to patient, but they included improved sputum production, atelectasis, exercise tolerance, and patient symptoms plus reduced need for medical care. These findings suggest that the addition of intermittent nasal CPAP to routine medical therapy may be of benefit to patients with severe TBM unresponsive to conventional medical management.