The effects of human recombinant granulocyte colony-stimulating factor (rhG-CSF) on leukocyte kinetics and immune function were assessed in patients with gynecologic malignancies receiving cytotoxic chemotherapy. Five day-rhG-CSF administration (50 mu g/m(2)/day) increased leukocyte counts in most of the chemotherapy courses. There was a significant difference in the leukocyte increase between the previously irradiated group and the nonirradiated group. An appreciable increase in LAK activity owing to an increased IL-2 production was noted after rhG-CSF administration. Despite a remarkable increase in the neutrophils observed, the CD57(+) cell count and NK activity in peripheral blood mononuclear cells were unexpectedly reduced.