Methanol extracts of Orostachys japonicus A. Berger (OAB) were found to exhibit apoptosis induction of HL60 human acute promyelocytic leukemia cells. Treatment of OAB exerted strong cytotoxicity against HL60 cells. OAB induced DNA fragmentation of HL60 cells in a dose dependent manner. Nitric oxide production were also increased in OAB-treated RAW264.7 macrophage cell lines. Treatment of OAB increased the expression of p53 and iNOS gene and the expression of p53, $NF-{kappa}B$ and iNOS protein in cultured HL60 and RAW264.7 cells. These results suggest that OAB are effective on strong anti-cancer properties and can be useful as a chemo-preventive agents.