Protein-polysaccharide fractions separated from nine Korean wild mushrooms were subjected to an in vitro screening test for lymphoblastogenic activity. Of these, PPLP, the protein-polysaccharide fraction of Lycoperdon pedicellatum, showed the most potent activity and were further investigated for its antitumor activity. When intraperitoneally injected into ICR mice once daily for six days at a dose of 30 mg/kg, PPLP strongly inhibited the growth of sarcoma 180 tumor cells, showing the inhibition ratio of 97.6%. PPLP also showed in vitro inhibitory activity on sarcoma 180 or leukemia L1210 at the concentration of 500 $mu extrm{g}$/$mell$ or higher. These results strongly suggest that PPLP might exert its antitumor activity through immunostimulation as well as inhibitory activity on the tumor cells.