Chronic neutrophilic leukemia is a rare myeloproliferative disorder. We have experienced a typical case of chronic neutrophilic leukemia in a 76-year-old man who complained abdominal distension due to hepatosplenomegaly. White blood cell count of peripheral blood was 50,500/nL with 90% segmented neutrophils. The underlying disease for a leukemoid reaction had not been detected. Leukocyte alkaline phosphatase score and the serum levels of vitamin B12 and uric acid were elevated. Chromosome study showed a normal karyotype without Philadelphia chromosome or bcr/abl rearrangement. Phorbol myristate acetate-activated respiratory burst activity of neutrophils measured with chemiluminescence showed increased activity.