Rats of the Sprague-Dawley strain were administered 2-acetylaminofluorene (2-AAF) in different diet regimens to ascertain the effect of retinoic acid(RA), butylated hydroxytoluene (BHT), propylgallate (PG), and selenium on induced hepatotoxicity. In the first study, groups of young male albino rats of the Sprague-Dawley strain were fed a diet containing 0.05% 2-AAF. Carcinogen was added to the diet for 3 weeks, omitted 1 week, added 2 weeks, omitted 2 weeks, added 3 weeks, and omitted for the final 4 weeks. Animals were terminated at the end of 15 weeks. Supplementation of the diet by 0.5% BHT, PG or 4 ppm selenium as sodium selenite in the drinking water either throughout the entire feeding period or only during the administration of the carcinogen-free diet greatly inhibited the hepatotoxicity of 2-AAF. In contrast, addition of 0.02% RA to the diet in the above feeding regimens enhanced the hepatotoxicity of 2-AAF. In the second study, male and female Sprague-Dawley rats were administered a diet containing 0.03% 2-AAF for 16 weeks or a diet containing 0.03% 2-AAF supplemented with 0.02% RA for the first 4 weeks and the last 6 weeks of the 16-week feeding period. Addition of the 0.02% RA to the diet enhanced the hepatotoxicity of 2-AAF, especially in the female rats.