The water-soluble (LEM) and alcohol-insoluble (LAP and LAP1) fractions were prepared from the culture medium of Lentinus edodes mycelia which was composed of bagasse and rice bran. LEM suppressed rat hepatocarcinogenesis and its cell proliferation of rat-ascites hepatoma to about 50% or less of each control group. LAP also suppressed cell proliferation at almost the same rate. LAP1 induced many small cells in the ascites and significantly raised the survival rate of hepatoma-bearing rats. Thus, anticarcinogenic action was revealed in LAP or LAP1 fractions which were mainly composed of xylose-containing polysaccharide and protein.