The more society has complicated, the more we have met stressful circumstance. And it is found that many physical and mental symptoms induced by stress. Soyosan(SYS) is one of the well-known oriental medicine for the treatment of general syndrome induced by emotional stress. This study was taken to know effects of SYS water extract on immune-depressed mice induced by stress. The results obtained in this study were as follows : 1. SYS inhibited murine weight-loss induced by stress 2. In vivo& in vitro, SYS increased phagocytic activity. 3. SYS enhanced the production of such reactive oxygen intermediates as superoxide and hydrogen peroxide from macrophages. 4. In vitro, SYS little influenced the production of reactive nitrogen intermediates. 5. SYS increased the number of the rosette forming cells of spleen. 6. SYS changed the ratio of helper and suppressor T cells by increasing $CD4^+$ T cells and decreasing $CD8^+$ T cells. 7. SYS increased cytotoxic activity on human lymphoma cell line(K562). 8. SYS increased the plasma level of GH and DHEA. whereas it decreased that of ACTH and cortisol. According to the above results, it might be considered that SYS would be used for immune-depressive disease induced by stress.