The purpose of this research was to investigate the effect of Cheongsimondam-tang(CSODT) on the activity of immune cell and anti-carcinogenic effect of mouse leukemia cell. The addition of CSODT(1 ㎍/ml) enhanced the proliferation of cultured-splenocytes and thymocytes. And also administration of CSODT(500 ㎍/kg) accelerated subpopulation of splenic and thymic T lymphocytes especially CD4⁺-T_H cells in BALB/c mice. CSODT treatment decreased cell proliferation and increased apoptotic cell death of cultured-L1210 leukemia cells, and induced apoptosis in addition to decreased mitochondrial transmembrane potential (ΔΨm) of transplanted-L1210 cells in vivo. These results suggest that CSODT have a cellular immuno-regulatory effect and anti-cancer property action.