In order to study the clinical usefulness of crude polysaccharides fractionated from Eleutherococcus senticosus, EN-3, in eliminating tumors, we have investigated the effect of combination therapy on the murine tumor metastasis and growth models. In experimental metastasis of colon26-M3.1 cells, prophylactic intravenous (i.v.) administration of EN-3 (0.5, 5, and 50 $mu extrm{g}$/mouse) inhibited tumor metastasis compared with tumor control group in 33.6, 66.8, and 81.8％ respectively. The administration of EN-3 (50 $mu extrm{g}$/mouse) also exhibited a 66.1％ therapeutic effect on lung tumor metastasis. Although EN-3 induced no toxic effect on both tumor cell and normal splenocyte in the concentration below 100 $mu extrm{g}$/mι in in vitro, it induced significant proliferating activity on normal splenocyte in the concentration-dependent manner. In an analysis of NK-cell activity, i.v. administration of EN-3 (4∼100 $mu extrm{g}$/mouse) significantly augmented NK cytotoxicity to YAC-1 tumor cells. The combination treatments of cisplatin (10 $mu extrm{g}$) and EN-3 (5 $mu extrm{g}$) induced synergistic effect on the inhibition of tumor metastasis in experimental tumor metastasis model produced by colon26-M3.1 cells. In addition, the combination treatments also exhibited prolongation of lifespan in S∼180 tumor bearing mouse for over the 60 days. Even though cisplatin (2.5 $mu extrm{g}$/mι) exhibited cytotoxicity to tumor cells and inhibited tumor growth over 95％ in in vitro, combination treatment with EN-3 (20 $mu extrm{g}$/mι) was induced splenocyte proliferation and produced cytokines, such as TNF-$alpha$, IL-1 and IL-12, from the macrophages. These results suggested that EN-3 stimulate immune system non-specifically and apply to the biological response modifiers (BRM) in chemo-immunotherapy for tumor prevention.