Z- Azoxybenzene has attracted limited investigational interest. An early stage investigation was conducted on rats to determine the effect of Z-azoxybenzene on liver enzymes. It was found that oral administration of azoxybenzene caused a time and dose-dependent decrease for cytochrome P-450 as well as in the ability of aminopyrine-N-demethylation and aniline hydroxylation. In both male and female rats, there was retardation in body weight gain and increases in relative liver weight, and an increase in the amount of microsomal cytochrome b5.