A 34-year-old woman with typical chronic myelogenous leukemia was treated with daily busulfan (total dose, 1600 mg approximately) from July 1978 to June 1981. In February 1981, she noticed a progressive deterioration of her clinical status, characterized by increasing dyspnea and productive cough. In July 1981, an open lung biopsy revealed pulmonary alveolar proteinosis. The patient died of progressive respiratory failure in August 1981. The association between chronic myelogenous leukemia and pulmonary alveolar proteinosis is briefly reviewed. The report discusses the possible etiologic role of busulfan therapy in the development of pulmonary alveolar proteinosis.