The purpose of this research was the comparative study of 3 kinds of black soybean on murine immune cells. The 3 kinds of black soybean are Glycine max Merr. with inner color-yellow (GY), Glycine max Merr. with inner color-greenish (GG) and Rhynchosia volubilis Lour. (RV). All of the black soybean increased the viability of murine thymocytes in vitro. The combined treatment of GY or GG and mitogen did not affect the viability of splenic T- and B-lymphocytes compared with mitogen-treated group, but the combined treatment of RV and mitogen increased their action compared with mitogen-treated group. Also, the 3 kinds of black soybean were given p.o. once a day for 7 days, respectively. RV increased the population of thymic-$CD8^+$, splenic-$CD8^+$ and $B220^+$ cells in vivo. Furthermore, GY and GG did not affect the phagocytic activity and the production of nitric oxide in peritoneal macrophages in vitro, but RV enhanced their action. These results suggest that immunopotentiative action of Rhynchosia volubilis Lour. is more potent than their of Glycine max Merr.