Astragali radix (AR) is one of the oldest and mast frequently used crude drug for traditional medicine in many Asian countries. This study designed to investigate the hepatoprotective effects of the aqueous extracted AR (ARE) against acetaminophen (APAP)-induced hepatic damage in ICR mice. APAP at the dose of 450 mg/kg i.p produced liver damage in ICR mice. Serum enzyme activities of alanine aminotransferase, aspartate aminotransferase and sorbitol dehydrogenese was dramatically decreased up to control level by pretreatment of ARE. However, hepatic glutathione level did not show a significant change between the tested groups. We also investigated TNF α mRNA gene expression on APAP-induced liver damage by RT-PCR. APAP dramatically induced TNF α mRNA gene expression in ICR mice. Pretreatment of mice with ARE led to a marked decrease of TNF α mRNA gene expression. These data indicate that 1) ARE has clearly revealed a hepatoprotective effect against APAP-induced hepatic damage in ICR mice, and 2) the protective effect of ARE may be, in part, associated with the regulation of TNF α mRNA gene expression.