The effects of scoparone, one of coumarin derivative on the hepatic bromobenzene metabolizing enzyme system was estimated in rats. Scoparone pretreatment revealed dose-dependently the recovery of decrease in epoxide hydrolase activity due to the bromobenzene(310 mg/kg, i.p.) treatment. And also scoparone and scopoletin (each 5mg/kg, p.o.) pretreatments showed two times increase in the $V_{max}$ values compared to those of bromobenzene-treated group which were calculated from tripartite reciprocal plots. The mode of protective effect of scoparone against bromobenzene induced toxicity is considered to be due to the induction of microsomal enzyme activity by scopoletin, the intermediate metabolite of scoparone. The changes in cytochrome P-450 activity, aminopyrine N-demethylation, aniline hydroxylation and glutathione S-transferation in scoparone-treated group were not significantly different from those of the control group.