Pulmonary alveolar proteinosis (PAP) is a disease of unknown etiopathogenesis sometimes associated with malignant haematological disorders. The potential reversibility of the process in these cases seems to be related to recovery from the underlying disease. GM-CSF has acquired an important, potentially pathogenic role and BMT presents one therapeutic option effective in certain forms of human PAP. We present the case of a 43-year-old female patient with Ph+ CML. During pretransplantation evaluation, unexpected pulmonary infiltrates were noted in the chest X-ray, PAP being diagnosed on biopsy. In view of the progressive respiratory symptomatology and her CML being in accelerated phase, the patient underwent haematopoietic transplantation. She died on day +12 from invasive pulmonary aspergillosis before a response could be observed. Pathogenic implications in PAP and the role of haematopoietic transplantation in this disease are discussed.