Chronic and acute ethanol treat nents increased th,: 3-hydroxybutyrate uptake by lactating rat mammary gland as :1 consequence of its high afferent concentration, without changing its relative extraction. The uptake of glucose was inhibited in the ethanol treated animals due to int ·insic alterations in the mammary gland metabolism as indicated by the decreased relative extrac1 ion and unchanged afferent concentration. These results would suggest that the ek:vated uptake of ketone bodies in ethanol-treated rats can be respcnsible, at least in part, for the decrease in glucose uptake by lactating rat mammary gland, although other direct effects of ethanol may be implied.