In liver microsomes of rats 5 h after intraperitoneal administration of bromobenzene, the activities of a series of drug-metabolizing mixed-function oxidases, i.e., ketamine and aminopyrine N-demethylases, methylayapanine and methoxybiphenyl O-demethylases, and ethoxycoumarin O-deethylase, as well as glutathione and cytochrome b5 contents were found to be decreased, whereas the activities of microsomal, NADPH-dependent cytochrome c and neotetrazolium reductases as well as cytochrome P-450 were unchanged.