Interstitial pneumonia and aseptic neutrophilic infiltration in the lung are rare pulmonary manifestations of myelodysplastic syndrome (MDS). We report a patient with progressive interstitial pneumonia associated with MDS. Histological examination of the lung revealed infiltration of atypical haematopoietic cells associated with MDS and diffuse alveolitis with honeycombing. Neutrophils obtained from the patient showed superoxide hyperproduction after stimulation with phagocytosis and phorbol myristate acetate, which might be attributed to the pathogenesis of interstitial pneumonia.