Ten therapeutic bronchopulmonary lavages were performed in four patients with pulmonary alveolar proteinosis. Chest radiographs taken during the lavage procedure showed increased density of the washed lung owing to the presence of instilled lavage saline. Radiographs obtained within the first hours after lavage showed a spectrum of change from minimal improvement to marked worsening compared with prelavage examinations. Subsequent radiographs over the next week showed gradual improvement in the treated lung. By 6 weeks there was moderate to marked improvement of chest radiographs compared with baseline in all cases.