To detect the effect of ginseng saponin on the immune response, mice were immunized with a protein antigen (gamma-globulin of chick). Blood was then drawn from them twice, after 10 days of the first immunization and after 10 days of the second immunization respectively, and measurements were made by ELISA method of the antibody titer in antiserum. In addition, mice that has been immunized with the same antigen were treated with immunosuppressor to suppress the immune system of the mice. After the immune system was suppressed, the effect of ginseng saponin on the recovery of immune response was measured by the same method. The experimental groups those were given ginseng saponin (10 mg/kg/day) showed a little variance between-individuals, however showed much higher antibody titer than the control groups those were given the saline solution. Moreover, there was a little recovery from the immune suppression. Although the mechanism of the effect of ginseng saponin on immune response was not well loom, it is believed that ginseng saponin has the effect of increasing the synthesis of serum protein together with its action as one of the immunostimulators.