Neutropenia is a major dose-limiting side effect of cancer chemotherapy. The therapeutic effects of CJ-50001 were examined on neutropenia caused by anticancer agents. Neutropenia was induced by cyclophosphomide (130 mg/kg), doxorubicin (4.5 mg/kg), and vincristine (1 mg/kg) in normal ICR mice and by cyclophosphamide (200 mg/kg) in CT26 adenocarcinoma bearing BALB/C mice. After the subcutaneous injection of anticancer agents, we administered subcutaneously recombinant human granulocyte-colonystimulating factor (100$mu$g/kg/day) to mice in order to stimulate neutrophil production. In normal and tumor-bearing mice, neutrophil production efficacy of CJ-50001 (rG-CSF) was similar to that of Grasin. These results suggest that CJ-50001 could be effective in its clinical use for neutropenia treatment.