ALTHOUGH infection is the most common cause of pulmonary infiltrates in patients with leukemia,<sup>1</sup>other diagnostic considerations include drug-induced disease, hemorrhage, infarction, leukoagglutinin reaction, congestive heart failure, and the leukemic process itself.<sup>2</sup>It is unusual for leukemic infiltration to be a major clinical problem, although pathologically it occurs relatively frequently.<sup>3</sup> <h3>Report of a Case</h3> A 35-year-old woman was admitted to the hospital on Nov 5, 1976, with fever and cough. Philadelphia chromosome-positive chronic myelogenous leukemia had been diagnosed in 1974 following a year of purpura. The patient had received intermittently busulfan, 4 to 8 mg/day for one year, at which time thioguanine was added. In January 1976 Bacillus Calmette-Guérin immunotherapy was instituted. Five months later, pleuropericarditis of unknown origin developed, and isoniazid therapy was given. In July 1976 early myeloblast transformation occurred. Demecolcine, thioguanine, prednisone, and vinblastine sulfate were given, and a splenectomy was performed. No further busulfan