The Korean formula medicine, Gami-Yukmi-Jihwang-Tang (GYJT) has been used for growing slowly, short of stature, incomplete development, fatigue, weak child, growing pain of child. However, it is still unclear how GYJT has an effect on experimental models. In the present study, the author investigated the immune-enhancing effect of GYJT. Forced swimming test (FST) was performed as a model of activity test in mice and measured blood urea nitrogen (BUN), aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactic dehydrogenase (LDH), glucose (Glc) and total protein (TP) in the serum. GYJT (1, 0.1 and 0.01 g/㎏) were orally administered to mice, once per day for 7 days using a feeding atraumatic needle. After 3 days, on FST, the immobility time was significantly decreased in the GYJT (0.01g/㎏/day)-fed group (120.75±5.71s) in comparison with the saline-fed group (153.80±10.74s). After 7 days, the immobility time was significantly decreased in the GYJT (0.1 and 0.01g/㎏/day)-fed group (125.67±5.36s and 107.67±3.71s) in comparison with the saline-fed group (167.67±12.99s). In addition, the contents of BUN and Glc in the blood serum were significantly decreased and the contents of AST, ALT and LDH were also decreased in the GYJT (1g/㎏/day)-fed group. However, the content of TP was not changed. The present results suggest that GYJT may be useful for the anti-fatigue and immune-enhancing agent. Also, the author investigated the effect of GYJT on the production of cytokines in human T-cell line, MOLT-4 cells. However, GYJT has not affected the production of IFN­γ, IL-2, IL-4. These results suggest that GYJT has immune-enhancing effect but does not affect T cell-mediated production of cytokines in the immune function improvement.