We previously reported that acidic polysaccharide from Panax ginseng induced the proliferation lymphocytes and the generation of activated killer cells. Here we found that polysaccharide (PG-75) precipitated with 75% EtOH from water extract of Panax ginseng also has both in vitron and in vivo hematopoietic activities. In vitro studied with bone marrow cells from BALB/c mouse revealed that PG-75 had direct effect on hematopoietic colony-forming cell(CFC) growth, increased granulocyte macrophage-colony forming cell numbers by 1.59 fold over than non-treated. the ability of PG-75 to modulate hematopoiesis in vivo was evaluated the bone marrow and spleen celluarity, granulocyte-macrophage progenitor cells. BALB/c female mice were administered G-75 intraperitoneally, PG-75 was found to significantly increase the number of BM cells, spleen cells, GM-CFU on 3 hours after injection. PG-75 was also able to induce significant augmentation of GM-CSF and IFN-${gamma}$, production in sera. These studies illustrate than PG-75 has hematopoietic activities and that this agent may be useful in the prevention and/or treatment of radio- or chemotherapy-associated myelosuppression.