The purpose of the present study was to assess the in vitro effect of some imidazole (prochloraz, imazalil) and triazole (epoxiconazole) agricultural fungicides on gonadotrop-ininduced oocyte maturation in rainbow trout. Results show that prochloraz, epoxiconazole and imazalil strongly potentiated the induction of oocyte maturation by gonadotropin in a dose-dependent manner. Furthermore, 10(-5) M prochloraz and epoxiconazole alone induced oocyte maturation. The mRNA biosynthesis inhibitor, actinomycin D, completely inhibited oocyte maturation induced by fungicides, suggesting that the gonadotropin-like effect of these chemicals is at least dependent on de novo gene expression.