We Previously reported that Polysaccharide Isolated from panax ginseng C. A. Meyer, stimulates murine splenocytes to proliferate and to be cytotoxic against a wide range of tumor cells in MHC non-restricted manner:) Therefore, we examined the cytokine mRNA expression induced by the ginseng polysaccharide in this paper. This study demonstrates that the ginseng polysaccharide stimulates Thl type cytosine expression such as IL-2 and IFNY, and macrophage type cytokine expression such as IL-lc and GM-CSF in a dose-dependent manner at different time: IL-2 mRNA was induced at 30 min, IL-la, GM-CSF mRNA at 3 hr, IFNY at 6 hr after the ginseng polysaccharide treatment. In contrast with these, Th2 type cytokine expression such as IL-4 and IL-5 was not induced. The generation of the ginseng polysaccharide-activated killer cells which was induced at the optimal doses of 50 pEyml was neutralized in the presence of anti-lL-2, anti-lFNy, anti-IL-l ${alpha}$ antibodies, showing the importance of these cytokines produced by the ginseng polysaccharide. In flow cytometry analysis, the blastogenesis of IgM+ cells was induced on day 3 and the number of Thy 1.21 cells, CD4+ and CD8+ cells was increased on day 5. The ginseng polysaccharide also induced blastogenesis of T cells. In conclusion, the ginseng polysaccharide may have considerable antitumor immunotherapeutic modality by stimulating the cytokine production from Thl cells and macrophage and by proliferating lymphocytes.