IL-3 has effects on a wide variety of cell types, including immature cells of the immune cells, and mature immune cells such as granulocytes. In the purpose of studying the immunoregulatory function of IL-3 and its potential role in cancer therapy, we established a IL-3-secreting tumor model using gene transfection to deliver locally IL-3 to tumor site. First, we constructed IL-3 expression vector BMGNeo-mIL-3, then transfected it into B16 murine melanoma cells. By G418 resistant screening and limiting dilution, we obtained a transfectant that expressed high levels of IL-3 (806U / ml) . The IL-3 expression of the transfectant was confirmed by Northern blot analyses. Although the wild-type B16 cells and the B16-Neo cells transfected with BMGNeo did not express IL-3, the IL-3 expression in B16 cells had no obvious effect on the in vitro proliferation of the transfectant. These results showed we had successfully established a IL-3-secreting tumor cell clone which would enable us to further study its in vivo tumorigenicity and immune function.