Tremella aurantialba, one of edible and medicinal mushrooms belonging to Tremellaceae of Basidiomycota, has been known to have outstanding curing effects on coughing, tracheitis and hypertension of humans and antitumor activity on the sarcoma 180 and Erhrlich carcinoma of mice. 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 tests showed that all crude polysaccharides extracted from the fruiting body were not cytotoxic against cancer cell lines such as RAW 309 CR.1 and Sarcoma 180 at the concentration of 2000 µg/ml. Intraperitoneal injection with crude polysaccharides exhibited life prolongation effect of 11.1~66.7% in mice inoculated with Sarcoma 180. Fr. MeOH improved the immunopotentiation activity of B lymphocyte by increasing the alkaline phosphatase activity by 1.16 folds at the concentration of 200 µg/ml. In case of Fr. HW, the numbers of peritoneal exudate cells and circulating leukocytes were increased by 1.42 and 2.87 folds, respectively.