Background and Objectives : Korean mistletoe lectin (Viscum album coloratum agglutinin, VCA) and bee venom (BV) have been reported to induce apoptosis in various cancer cell lines in vitro and to show antitumor activity against a variety of tumors in animal models. However, the comparative effect of VCA and BV on the anti-cancer effect and mechanisms of action has not been determined. In this study, the effect in a human hepatocellular carcinoma cell line, Hep G2 cells, was examined. Methods : Cytotoxic effects of VCA and BV on Hep G2 cells were determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay in litro. The apoptotic cell death was then confirmed by propidium iodide staining and DNA fragmentation analysis. The mechanisms of action were examined by the expression of anti-apoptotic proteins and activation of mitogen-activated protein kinases. The involvement of kinase was examined in VCA or BV-induced apoptosis by using kinase inhibitors. Results : VCA and BV killed Hep G2 cells in a time and dose-dependent manner. Treatment of Hep G2 cells with VCA activated poly (ADP-ribose) polymerase-1 (PARP-1) known as a marker of apoptosis, and mitogen-activated protein kinases signaling pathways including MAPK/ERK, p38 MAPK and JNK. BV also activated PARP-1, MAPK/ERK. and p38 MAPK but not JNK. The expression level of anti-apoptotic molecule, Bcl-X, was decreased by VCA treatment but not by BV. Finally, the phosphorylation level of ERM proteins involved in the cytoskeleton homeostasis was decreased by both stimuli. VCA-induced apoptosis was partially inhibited by in the presence of JNK and p38 inhibitor, but BV only by p38 inhibitor. Conclusions : VCA-induced apoptosis is dependent on the activation of p38 and JNK. while BV-induced apoptosis is mediated by p38 activation in Hep G2 cells.