['Non-alcoholic fatty liver disease (NAFLD) and viral hepatitis are associated with hepatic oxidative stress, which is partially dependent on the amount of hepatic fat.', 'To determine whether the circulating lipid and oxidative stress parameters could be non-invasive markers of hepatic steatosis.', 'Sixty-four patients with NAFLD or viral hepatitis were tested for lipid peroxidation products and antioxidant defence systems, lipid parameters and liver function tests.', 'Hepatic steatosis was correlated with lipids, gamma-glutamyltranspeptidase, thiobarbituric acid-reactive substances, superoxide dismutase and superoxide dismutase/erythrocyte glutathione peroxidase ratio. gamma-Glutamyltranspeptidase, triglycerides and low-density lipoprotein cholesterol were significantly higher in the presence of steatosis. No difference in blood oxidative stress markers was observed according to the presence or absence of steatosis except for the superoxide dismutase/erythrocyte glutathione peroxidase ratio. Total cholesterol, triglycerides and low-density lipoprotein cholesterol were significantly higher in the NAFLD group (n = 17, 60% mean steatosis grade) than in the viral hepatitis group (n = 20, 13% mean steatosis grade). Only superoxide dismutase was lower and vitamin E higher in NAFLD than in viral hepatitis patients.'] Are blood oxidative stress markers unreliable markers of hepatic steatosis?