Armillaria mellea, one of edible and medicinal mushroom belonging to Tricholomataceae of Basidiomycota, has been known to have outstanding inhibitive effects on the sarcoma 180 and Erhrlich carcinoma of mice. Neutral salt 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 the mushroom. In vitro cytotoxicity tests, crude polysaccharide were not cytotoxic against cancer cell lines such as NIH3T3 and Sarcoma 180 at the concentration of 1000 µg/ml. Intraperitoneal injection with crude polysaccharides exhibited life prolongation effect of 60~67.5% in mice inoculated with Sarcoma 180, respectively. Fr. NaCl improved the immunopotentiation activity of B lymphocyte by increasing the alkaline phosphatase activity by 1.8~3.0 folds, respectively. In case of Fr. NaCl, the numbers of peritoneal exudate cells and circulating leukocytes were increased by 10 and 2 folds, respectively.