The present study was performed to investigate the innate immune stimulating effects of the polysaccharide fraction (VL-3IIb) from peel of grape (Vitis labrusca). VL-3IIb treatment of peritoneal macrophage produced various cytokines (IL-6, IL-10, and IL-12) in vitro experiment. The intravenous (i.v.) administration of VL-3IIb in mice ($100{mu}g/mouse$) significantly augmented cytotoxicity of natural killer (NK) cells against Yac-1 tumor cells. The i.v. administration of VL-3IIb ($50-500{mu}g/mouse$) 2 days before tumor inoculation significantly inhibited lung metastasis of colon26-M3.1 carcinoma cells in a dose-independent manner. In addition, the depletion of NK cells by injection of rabbit anti-asialo GM1 serum abolished the inhibitory effect of VL-3IIb on lung metastasis of colon26-M3.1 cells. These results indicate that VL-3IIb has antitumor activity to inhibit tumor metastasis prophylactically, and its antitumor effect is associated with activation of macrophages and NK cells.