WooKiEum (WKE) has been used for the purpose of the development of increased immune-system strength in Korea. In the present study, we examined the anti-immobility effect of WKE on the forced swimming test (FST), and then measured blood biochemical parameters related to fatigue: glucose (Glc), blood urea nitrogen (BUN), lactic dehydrogenase (LDH), creatinine, and total protein (TP). WKE (0.1, 1 g/kg) was administered orally to mice for 7 d. After 2 d, the immobility time was decreased in the WKE-administered group. After 7 d, the immobility time was significantly decreased in the WKE-administered group (64.6+/-9.0 s for 0.1 g/kg) in comparison with the control group (101.3+/-32.7 s). In addition, amount of Glc in the blood serum was increased, whereas the contents of BUN, LDH and TP decreased in the WKE-administered group. Next, we investigated the effect of WKE on the production of cytokines in a human T-cell line, MOLT-4 cells and mouse peritoneal macrophages. WKE (1 mg/ml) significantly increased interferon (IFN)-gamma and TNF-alpha production compared with the media control (about 2.2-fold for IFN-gamma, about 1.7-fold for TNF-alpha, p<0.05) after 24 h. WKE increased the protein expression of IFN-gamma in MOLT-4 cells. These results suggest that WKE may be useful in immune function improvement.