Recently many investigators have initiated searches for immunomodulating substances from natural food sources. Ginger (Zingiber officinale Roscoe) has been used as a raw material in many traditional preparations since the ancient time. This study was performed to investigate the immunomodulative effects of Zingiber officinale Roscoe in mice, using ex vivo experiments. In order to elucidate the immunomodulative effects of Ginger, water extracts of the plant were orally administrated into mice, and isolated splenocytes and macrophages were used as experimental model. In order to identify its ex vivo effect six to seven week old Balb/c mice were fed ad libitum on a chow diet and water extracts of ginger were orally administrated every other day for two weeks at two different concentrations (50 and 500 mg/kg b.w.). After preparing the single cell suspension, the proliferation of splenocytes was determined by MTT assay. The result of ex vivo study showed that the highest proliferation of splenocytes and macrophage activatation was seen in the mice orally administrated at the concentration of 500 mg/kg b. w. of ginger water extracts. In conclusion, this study suggests that ginger extracts nay enhance the immune function by regulating the splenocyte proliferation and cytokine prodution capacity by activated macrophages in mice.