A human hepatoma cell line, Hep G2 cells are reliable for the study of alcohol-induced hepatotoxicity. In this study, we investigated the effect of an aqueous extract of Polygala tenuifolia WILLDENOW (Polygalaceae) roots (PTAE) on ethanol (EtOH)-induced cytotoxicity in Hep G2 cells. PTAE (0.01-1 microg/ml) dose-dependently inhibited the EtOH-induced interleukin-1alpha (IL-1alpha) secretion. PTAE (0.01-1 microg/ml) also inhibited the EtOH- and IL-1alpha-induced cytotoxicity. Furthermore, we found that PTAE inhibited the IL-1alpha-induced apoptosis of Hep G2 cells. These results suggest that PTAE may prevent the EtOH-induced cytotoxicity through inhibition of the apoptosis of Hep G2 cells.