It is well-documented that alcohol drinking together with hepatitis viral infection accelerates liver injury; however the underlying mechanisms remain unknown. In this paper, we demonstrated that primary hepatocytes from transgenic mice overexpressing hepatitis B virus X protein (HBX) were more susceptible to ethanol- and TNF-α-induced apoptotic killing. Compared to normal control mouse hepatocytes, ethanol and/or TNF-α treatment led to a significant increase in reactive oxygen species, mitochondrial permeability transition, cytochrome C release,caspase-3 activity, and poly (ADP-ribose) polymerase degradation in hepatocytes from HBX transgenic mice.Blocking caspase-3 activity antagonized ethanol- and TNF-α-induced apoptosis in primary hepatocytes from HBX transgenic mice. Taken together, our findings suggest that HBX sensitizes primary mouse hepatocytes to ethanoland TNF-α-induced apoptosis by a caspase-3-dependent mechanism, which may partly explain the synergistic effects of alcohol consumption and hepatitis B virus infection on liver injury.