The administration of nickel to rats resulted in enhanced hepatic lipid peroxidation, levels of glutathione and iron with a concomitent decrease in glutathione peroxidase activity. These effects were dose dependent. Enhanced lipid peroxidation was found to be inhibited by the exogenous addition of ethylenediamine tetraacetic acid (EDTA), benzoate and ethanol while catalase and superoxide dismutase were ineffective in this regard. Our data strongly suggest the involvement of hydroxyl radicals in the nickel mediated enhancement of lipid peroxidation which may have their implications in the carcinogenicity of nickel compounds. © 1987 Academic Press, Inc.