In the previous report, we described the marked antitumor and immunomodulatory activities of PVp, a protein-polysaccharide fraction of a Korean wild mushroom Psathyrella velutina. In this study, a protein-polysaccharide fraction, PVMP, was prepared from the shake-cultured mycelia of the same mushroom and its immunoactivities as well as chemical compositions were investigated. At 200 $mu extrm{g}$/ml, PVMP weakly stimulated the BALB/c mouse splenic lymphocytes to form lymphoblasts and upregulated the expression of CD25 molecules, but failed to stimulate peritoneal macrophages. In chemical analysis these two protein-polysaccharide fractions were found to be quite different in that the carbohydrate contents of PVMP and PVP, respectively, was 85.3% and 41.2%. These results reveals that PVMP, unlike PVP, is a moderate immunostimulator on the immune system.