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The effects of adrenaline and adrenoreceptor antagonists on ovulation and follicle wall contraction were investigated in brook trout (Salvelinus fontinalis) follicles using in vitro incubation systems. Adrenaline significantly stimulated a dose-dependent increase in ovulation and follicle contraction at concentrations between 1.0 and 100 μmol l⁻¹ The ovulatory and contractile effects of 10 μmol adrenaline l⁻¹ could be blocked by the α₁-adrenoreceptor antagonists WB-4101 and benoxathian, and by the α₂-antagonist yohimbine. WB-4101 was the most potent blocker, significantly inhibiting ovulation and contraction at 1.0 μmol l⁻¹. In contrast, the β-antagonist propranolol (100–0.001 μmol l⁻¹) was totally ineffective in blocking adrenaline-induced ovulation and follicle contraction. The results indicate that there is a strong correlation between the effects of adrenaline on ovulation and contraction. In addition, the antagonist studies indicate that adrenaline stimulates ovulation and follicle contraction of brook trout follicles through α-adrenoreceptors.