Pulmonary alveolar proteinosis (PAP) developed in 5 patients with hematologic malignancy or lymphoma. Possible pathogenetic mechanisms which might predispose the patient to this association include the unavailability of competent alveolar phagocytes secondary to profound leukopenia, or inhibition of alveolar phagocytosis by elevated globulins. The spectrum of pulmonary abnormalities produced by PAP includes classical butterfly perihilar alveolar consolidation, lobar consolidation, parenchymal nodules, and hilar adenopathy. Four of the 5 cases had complicating infections, making the exact radiological correlation with PAP difficult.