Ginseng components were examined for their ability to modify immunotoxicity of cyclophosphamide. Ginseng polysaccharide fraction (FO, 300 mg/kg) inhibited decreases in the ratio of spleen to body weight, white blood cells (WBC) count and the number of plaque forming cells (PFC) induced by cyclophosphamide (50 mg/kg, i.p.), and increased these variables in normal mice. Ginseng saponin fraction (50 mg/kg) showed to increase hemoglobin content as well as the number of PFC/spleen in normal mice. on the other hand, Panaxytriol (20 mg/kg) Prevented decrease in mc count by cyclophos phamide. Neither saponin fraction nor panaxytriol had any significant effect on the number of PFC and antibody titers in cyclophosphamide-treated mice. These results suggest that ginseng polysaccharine fraction may reduce the immunotoxicity of cyclophosphamide and may be effective in stimulating immune function in normal mice.