We present the case of a male patient, aged 45 yrs, with malignant mesothelioma producing granulocyte colony-stimulating factor (G-CSF). The diagnosis was established by histopathological examination of the autopsied pleural tissues. Production of G-CSF was confirmed by immunoperoxidase staining, using a specific monoclonal antibody against recombinant G-CSF (rhG-CSF).