A 70-yr-old man developed cough, chest pain, hemoptysis and a pulmonary infiltrate shortly after initiation of treatment with chlorambucil for chronic lymphocytic leukemia. Chlorambucil was discontinued and an open lung procedure was performed with complete excision of the pulmonary lesion. The biopsy specimens showed histological alteration consistent with the diagnosis of bronchiolitis obliterans organizing pneumonia (BOOP). There was no evidence of other known causes usually associated with BOOP. The patient recovered completely after surgery. This report suggests that BOOP must be considered in the differential diagnosis of respiratory symptoms and pulmonary infiltrates in patients treated with chlorambucil.