Arsenic trioxide (As₂O₃), a major ingredient of Traditional Chinese Medicine (TCM), is found to be an effective anticancer drug in acute promyelocytic leukemia (APL). The present study explored the use of As₂O₃ on human hepatocellular carcinoma by in vitro study. The study showed that the clinically achievable concentration of As₂O₃, i.e. 2μM, inhibited the cell proliferation of human hepatocellular carcinoma cell line, HepG2, in a time-dependent manner. The mechanistic study showed that 2μM of As₂O₃ acted through induction of apoptosis in which caspase-3 was activated. The results also suggested that mitochondria did not take part in As₂O₃-induced apoptosis.