A patient with chronic idiopathic neutropenia, who had been suffering from repeated infections, was successfully treated with recombinant granulocyte stimulating factor (rhG-CSF). Subcutaneous injection of 30 micrograms/m2 rhG-CSF every two days was sufficient to maintain the neutrophil count at approximately 1,000/microliter. The patient has lived without any evidence of infection for the last 10 months using that treatment. There were no side effect caused by rhG-CSF and antibodies against G-CSF were not detected in the patient's plasma.