Dihydroergotoxine (DHET) decreased voluntary ethanol intake in rats selected for their stable ethanol preference (mean daily ethanol intake 8 g/kg). DHET inhibition was markedly potentiated by thioridazine. The potentiation is explained with a synergistic inhibitory effect on dopaminergic transmission: that is, DHET acting on dopamine (DA) autoreceptors and thioridazine preferentially inhibiting postsynaptic DA receptors.