Since the original description of pulmonary alveolar proteinosis in 1958 (19), more than 100 cases have been reported. This article indicates the wide spectrum of roentgenographic changes (other than the well known batwing appearance) by reference to 5 patients in the San Francisco area who were examined recently. The classic butterfly pattern formed by infiltrates radiating from the hili and suggestive of pulmonary edema is not seen in as many patients as the earlier case reports suggested. When present, its differentiation from pulmonary edema is based on much less dyspnea in patients with pulmonary alveolar proteinosis (PAP), normal size of heart, and caliber of pulmonary vein. Also, Kerley's B lines or pleural effusion are absent. In patients with longstanding PAP, cor pulmonale may supervene. This adds further diagnostic problems by the presence of cardiomegaly and pleural effusions. The butterfly appearance may resolve almost completely within a week (18), but the overnight clearing seen in some pat...