Many antitumor and immune modulating components have been isolated from fungal extracts. In this study, the authors isolated the proteoglycans from cultured mycelia of Lentin us lepideus, including especially the acidic polysaccharide fraction, named lepidan. It was obtained by extraction with hot water followed by purification using DEAE cellulose anion exchange. To elucidate antitumor effects against different type of tumor, the proteoglycans were tested on sarcoma 180, C3H MCA clone 16 and P388 leukemia in vivo. Lepidan showed 58.3% of tumor inhibition against solid form of sarcoma 180 and 58.6% against MCA clone 16. But lepidan did not affect life span of mice against P388 leukemia. Also when Lepidan was applicated to MTT assay, it did not show any direct cytotoxicity against various tumor cells in vitro.