Pulmonary failure is a major contributor to morbidity and mortality during marrow aplasia following high-dose antineoplastic therapy. For this reason, we initiated a pulmonary surveillance program for patients undergoing high-dose chemotherapy for leukemia or bone marrow transplantation. As part of this program, bronchoscopy with BAL was performed prior to therapy and at the onset of granulocytopenia. Thirty-three of the first 57 patients managed in this program developed some evidence of pulmonary complications. Twelve patients died in aplasia; all had pulmonary failure. Forty patients had clinically significant abnormalities on the bronchoscopy before treatment including 12 of 19 patients who had normal findings on chest x-ray films, physical examination, and pulmonary function testing, and no fever. Twenty-seven patients had clinically significant abnormal bronchoscopy or BAL at the onset of granulocytopenia. Thirteen patients required additional bronchoscopy. No patient required an open lung biopsy. Pulmonary surveillance using bronchoscopy with BAL is useful in the detection of pulmonary disease prior to the initiation of and following high-dose antineoplastic therapy.