Objective:The purpose of this study was to evaluate the effects of Enterococcus faecalis FK-23(FK-23) on the immune function in mice. Methods:Mice were treated with three doses of the FK-23(0.05, 0.1, 0.2, 0.6 g/kg body weight) for 30 days. Delayed type hypersensitivity (DTH), monocyte phagocytic function, serum hemolysis antibody and natural killer cell activity were studied. Results:The significant increases in mice treated with 0.6 g/kg bw were found in DTH, phagocytic function of monocyte, serum hemolysis antibody and natural killer cell activity. Conclusion:The results from the present study suggest that FK-23 could improve both specific and non-specific immune function.