The therapeutic evaluation of rG.CSF has been studied on neutropenic patients receiving lung cancer chemotherapy with focusing the change in the absolute neutrophil counting (ANC) in the patients during chemotherapy and subsequent rG.CSF treatment by daily dosing either at 0.4, 2.0, 5.0 and 10.0 micrograms/kg intravenously or at 2.0 and 5.0 micrograms/kg subcutaneously. The daily rG.CSF dosing for 14 consecutive days was performed on the patients upon completion of the 28-day chemotherapy for lung cancer. As a result, remarkable recovery of ANC was observed in the patients administered at doses of more than 5 and 2.0 micrograms/kg intravenously and subcutaneously, respectively. Additionally, the shortening of the neutropenia (ANC: below 1,000/cmm) was observed in the patients at doses of not less than 2.0 micrograms/kg in both administration routes. In conclusion, rG.CSF treatment demonstrates the completion and/or shortening of the chemotherapy cycle for lung cancer at a subcutaneous dose of 2.0 micrograms/kg and at a intravenous dose of 5.0 micrograms/kg. No adverse drug effects were observed in all patients during the study.