We have studied bronchopulmonary lesions that developed in 3 allogeneic bone marrow recipients between days 120 and 250 post-transplant. Two cases had extensive chronic GVHD at the time of onset. All patients complained of low-grade fever, dry cough, and shortness of breath. The bronchopulmonary lesions were characterized by hypoxemia with increased AaDO2 and bilateral multiple noncircumscribed interstitial shadows on chest CT scan. Broncho-alveolar lavage (BAL) showed elevated numbers of lymphocytes in BAL fluid in all cases. BAL fluid was negative for CMV, pneumocystis carinii cysts, bacteria and fungi in all cases. The results of transbronchial lung biopsy (TBLB) showed interstitial infiltration of lymphocytes in all 3 cases. The bronchopulmonary lesions were improved by either starting or increasing the dose of immunosuppressants. These findings and clinical courses suggest that the bronchopulmonary lesions in these patients were related to chronic GVHD.