We administered recombinant human granulocyte colony-stimulating factor (rhG-CSF) intravenously for 2 weeks to 2 elderly patients with severe neutropenia. The absolute neutrophil count (ANC) recovered promptly after the initiation of rhG-CSF therapy and reached a peak (greater than 10 x 10(9)/l) on the 13th day. The ANC fell rapidly after rhG-CSF was discontinued, but it remained within the normal range after therapy. There were no side effects during the entire course of treatment. Therefore, rhG-CSF seems to be a most beneficial treatment in elderly patients with severe neutropenia.