The purpose of this research was to investigate the effect of Sabaek-San(SBS) on the activity of immune cell and leukemia cell. The addition of SBS(1 ㎍/㎖) enhanced the proliferation of cultured-splenocytes and thymocytes. And also, administration of SBS(250, 500 mg/kg) accelerated subpopulation of splenic T lymphocytes in BALB/c mice. Administration of SBS eminently enhanced the production of IFN-γ, and IL-4. The treatment of high dose of SBS inhibit the proliferation of Jurkat cells and dose-dependently increased the apoptosis of cultured-Jurkat leukemia cells. These results suggest that SBS have a cell mediated immuno-regulatory effect.