To find physiologically active components of Korean higher fungi, high molecular weight fractions of the water extract of the cultured mycelia of Stropharia rugosoannulata were subjected to antitumor test against sarcoma 180 cells implanted in ICR mice. The partially purified fraction, Fraction A, was further purified by DEAE Sephadex A-25 column chromatography and Sephadex G-200 gel filtration chromatography. Fraction A inhibited the tumor growth at the ratio af 56.80% at a dose of 20 mg/ kg/day. It contained 22.73% polysaccharide and 30.30g protein. The polysaccharide moiety consisted of glucose, mannose, galactose, xylose and fucose. The protein moiety contained 17 amino acids, including aspartic and glutamic acids. When Fraction A was examined for immunological activity to elucidate mechanisms of its antitumor activity, it increased peritoneal exudate cells including macrophages, lymphocytes and polymorphonuclear leucocytes after 24 hours. It increased the number of hemolytic plaque-forming cells 22 times to that of the control group.