Exposure to ethanol is recognized to cause reproductive impairment in man and animals. Since elevated levels of prolactin will interfere with normal functioning of the hypothalamic-pituitary-gonadal axis, and since ethanol has been shown by others to lead to increased prolactin secretion in vivo, the present in vitro study was undertaken to determine whether there is a direct effect of ethanol (ETOH) on prolactin release. Prolactin release from anterior pituitary cells maintained in monolayer culture and exposed to either no ethanol or media containing ethanol at concentrations of 50, 100, 200, or 400 mg% was measured at 1, 4, 24, 48, 72 hours in incubation. Ethanol added directly to pituitary cells stimulated prolactin release at all time points examined. Significant stimulation occurred with addition of low and mid-range ethanol concentrations (50-200 mg%); no augmented prolactin secretory response was seen with the highest ethanol concentration used (400 mg%). This pattern of response was maintained throughout the entire 72 hour incubation period. Thus, the effect of ethanol on prolactin secretion is mediated, at least in part, at the anterior pituitary level.