We report an autopsied case of a 74-year-old man with primary pulmonary squamous cell carcinoma (SCC) associated with leukocytosis, hypercalcemia, phagocytosis in the bone marrow, reactive lymphadenopathy and mesangial cell proliferation in the glomerulus. Laboratory examination revealed increased serum levels of parathyroid hormone-related peptide (PTH-rP), granulocyte colony stimulating factor (G-CSF), interleukin-6 (IL-6) and soluble interleukin 2 receptor (s-IL2R). An autopsy showed moderately differentiated SCC at the left lower lobe of the lung, of which tumor cells distinctly showed cytoplasmic immunoreactivity to anti-G-CSF and anti-PTH-rP antibodies. Thus, pulmonary SCC seemed to produce both G-CSF and PTH-rP, causing leukocytosis, hypercalcemia, and IL-6 production from the bone. IL-6 also might have stimulated the proliferation of SCC and glomerular mesangial cells, and induced phagocytosis, reactive lymphadenopathy and hepatosplenomegaly by interacting with the mononuclear phagocytic system.