80% methanol and 0.9% neutral saline soluble and hot water substances (hereinafter referred to Fr. NaCl, Fr. HW and Fr. MeOH, respectively) were extracted from fruiting bodies of Grifola frondosa. In vitro cytotoxicity tests, crude polysaccharides were not cytotoxic against cancer cell lines such as Sarcoma 180 and RAW 264.7 at the concentration of 10~2000 µg/ml, but crude polysaccharides from Fr. NaCl was slightly toxic to HT-29 and NIH3T3 at the concentration of 2000 µg/ml. Intraperitoneal injection with crude polysaccharides exhibited life prolongation effect of 25.0~52.9% in mice previously inoculated with Sarcoma 180. Fr. HW increased the numbers of spleen cells by 1.3 fold at the concentration of 200 µg/ml compared with control. Fr. NaCl improved the immuno-stimulating activity of B lymphocyte by increasing the alkaline phosphatase activity by 1.5 fold compared with control at the concentration of 200 µg/ml. 10~14 µM of nitric acid were generated when Fr. NaCl was added to RAW 264.7 at the concentration of 50~500 µg/ml, while the control group produced 4.3 µM of nitric oxide. The Fr. NaCl, Fr. HW and Fr. MeOH increased the production of TNF-α, IL-1β, Il-2 and IL-6 by more than 1.4 times compared with the control group. The Fr. of MeOH increased the numbers of peritoneal exudate cells and circulating leukocytes by 3.0 and 2.0 folds compared with the control at the concentration of 50 µg/ml, respectively. Therefore, the crude polysaccharides extracted from fruiting bodies of Grifola frondosa could improve antitumor activity of mice.