Oudemansiella radicata, edible and medicinal mushroom belonging to Agaricales of Basidiomycota, has been known to exhibit outstanding curative effects on the fungal infection and hypertension caused by high blood pressure. Neutral saline soluble (0.9% NaCl), hot water soluble and methanol soluble substances (hereinafter referred to Fr. NaCl, Fr. HW and Fr. MeOH, respectively) were extracted from fruiting body of the mushroom. In vitro cytotoxicity test showed that Fr. NaCl was not cytotoxic against NIH3T3 and Sarcoma 180 at the concentration of 10~1,000 µg/ml. Intraperitoneal injection with Fr. NaCl exhibited antitumor activity with life prolongation effect of 42.9~66.7% in mice inoculated with Sarcoma 180. Fr. NaCl improved the immunopotentiating activity of B lymphocyte by increasing the alkaline phosphatase activity by 1.4~3 folds compared with controlled and LPS groups, respectively. Intraperitoneal injection with Fr. MeOH increased the numbers of peritoneal exudate cells and circulating leukocytes by 3.5 and 2.5 folds, respectively. Therefore, the antitumor effect exhibited on mouse Sarcoma 180 cells was likely due to immuno-modulating activity of crude polysaccharides extracted from fruiting body of O. radicata.