Using harmol and paracetamol as the substrates, the elevation of conjugation reactions by BHA feeding and their significance towards the protective effects of this antioxidant has been studied with hepatocytes obtained from mice. With both substrates, an almost five fold elevation of the glucuronidation was observed. However, there was no change in the rate of sulfate conjugation. The rate of glutathione conjugate formation with paracetamol was also not enhanced, even though both the GSH level and glutathione S-transferase activities were increased. Finally, BHA administration afforded no protective effect against the hepatotoxic effects of paracetamol, even when the production of reactive paracetamol metabolites was increased by 3-methylcholanthrene pretreatment.