The effects of acute administration of alcohol on suckling-induced prolactin (PRL) release and milk yield were studied in primiparous lactating rats. On lactation day 2, pups were culled to 8 per litter. On day 5, dams were implanted with atrial catheters. On day 10, pups were separated from the dams at 0900 hr; at 1300 hr, an extension containing heparin (50 IU/ml) and 0.9% saline was attached to the exteriorized portion of the catheter. At 1400 hr, 0.4 ml blood was removed and replaced with 0.9% saline (control) or 0.3, 0.5 or 1.0 g/kg body weight of alcohol. At 1500 hr a second blood sample was obtained followed by a second alcohol or saline infusion. Pups were returned to dams and blood samples were obtained 10, 30, and 60 min after suckling. Milk consumption was calculated by weighing pups before and after 60 min of suckling. PRL in plasma samples was measured by radioimmunoassay. Alcohol did not alter baseline serum PRL. However, suckling-induced PRL release and milk consumption by the pups were significantly inhibited. Since basal PRL was not altered following administration of alcohol, the inhibitory effect of alcohol on suckling-induced PRL release is attributed to a disruption of transmission of the impulse arising from suckling stimulus.