Pulmonary alveolar proteinosis (PAP) has been reported in 5 patients with chronic myelogenous leukemia and approximately 20 patients with other hematologic malignancies. These patients have had recurrent infections, frequently by opportunistic organisms. This susceptibility suggests that they have impaired cell-mediated immunity. In the case reported, splenectomy early in the course of illness may have contributed to the susceptibility to infection and PAP. Awareness of the possibility of pulmonary alveolar proteinosis in a patient with progressive dyspnea and unexplained pulmonary infiltrates should prompt early open lung biopsy to establish the diagnosis. Therapeutic pulmonary lavage is currently the treatment of choice.