The objective of this paper was to determine the antitumor activities of aqueous extracts of seven species of edible mushrooms occurring in Japan. There are seven species involved which are Lentinus edodes, Flammulina velutipes, Pleurotus ostreatus, Pleurotus spodoleucus, Pholiota nameko, Tricholoma matsutake and Auricularia auricula-judae. Materials and method used in this study were Swiss albino mice which have implanted with tumor cell. After that, these mice were injected with 200 mg/kg/day doses of sample materials for 10 days. Then, the tumor growth is observed for five weeks and the tumor weighed between treated mice and untreated mice. Ten gm of the extract of Lentinus edodes (Berk.) Sing. was dissolved in about 200 ml of water and purified by passage through a 6 x 50 cm column of Duolite A-7 or 5-30 (acetateform) ion-exchange resin. The process continuously with eluted with 300 litres of water. After that, adding 10 volumes of acetone, precipitate was centrifuged, washed with acetone several times, and dried. A 5% yield of white powder was obtained. The column was then eluted with 3liters of 0.25 N sodium hydroxide. After neutralization, 3 volumes of ethanol added to obtain precipitation. As the result, all of aqueous extracts except Auricularia auricula-judae highly inhibited the growth of transplanted tumor. The level tumor inhibition of this material towards Sarcoma 180 shows most effective of the materials produced by Lentinus edodes (Berk.) Sing.