We have recently treated a case of autoimmune neutropenia in a 57-year-old male. Because neutropenia persisted despite the administration of prednisolone for 30 days, daily subcutaneous injection of human recombinant granulocyte colony-stimulating factor (rhG-CSF) at a dosage of 100 micrograms was started. Neutrophil count increased gradually and reached a plateau of 5,000/microliters by day 25 after administration of rhG-CSF. This observation suggests that rhG-CSF is effective for the treatment of autoimmune neutropenia.