We investigated the immune enhancement effects of JaSaengHwan (JSH). The forced swimmingtest (FST) has been used as a screening model for new immune enhancement agents. We foundthat JSH (0.1 mg/ml) significantly reduced the immobility time in the FST compared to thecontrol. Also, we investigated the effect of JSH on the proliferation of T cell and production ofcytokines in human T-cell line, MOLT-4 cells and mouse peritoneal macrophages. JSH (1 mg/ml)significantly increased the cell proliferation by 46.78±6.41% (P<0.05) and also significantlyincreased the interleukin (IL)-2, IL-4 and interferon (IFN)-g production compared with mediacontrol (about 2-fold for IL-2, 3-fold for IL-4 and 1.5-fold for IFN-g, P<0.05) at 24 h. In addition,JSH increased the production of IL-12 on the mouse peritoneal macrophages (by 3.6-fold for IL-12,P<0.05). In conclusion, these data indicate that JSH may have an immune-enhancement effect.