The hepatoprotective activity of the 50% ethanol extract of the bark of Lawsonia alba syn. L. inermis was investigated against the carbon tetrachloride-induced oxidative stress. Pretreatment of rats with doses of 250 and 500 mg/kg of the plant extract significantly (P<0.001) lowered serum transaminases (GOT and GPT) and LDH levels, respectively, in a dose dependent manner against the significant (P<0.001) rise of these damage marker enzymes when challenged with CCl4 (1 ml/kg, orally). Parallel to these changes, the plant extract prevented CCl4-induced oxidative stress by significantly maintaining the levels of reduced glutathione (GSH), its metabolizing enzymes and simultaneously inhibiting the production of free radicals. Pretreatment of rats with the extract also inhibited the peroxidation of microsomal lipids in a dose-dependent manner. © 2000 Elsevier Science Ireland Ltd.