This experiment was performed to investigate the effects of ginseng saponin fraction and cyclophosphamide (CY) on the tumor development, the antitumor effect and the tumoricidal activity of mouse macrophage. When mice were treated with saponin or CY following inoculation with Sarcoma 180, tumor development was inhibited and survival ratio increased, and a combination of both treatments further inhibited the tumor development. Tumoricidal activity of macrophage was effectively increased at 10-7% concentration of CY and it was further increased when macrophage was cotreated with saponin and CY. Tumoricidal activity of macrophage was greatest at the third day after inoculating tumor cell. Both saponin and CY increased the chemiluminescence of macrophage, but CY had no effect on releasing TNF, unlike saponin.