The effects of 250 mg/100 ml ethanol on the efflux of 3,4-dihydroxyphenylacetic acid (DOPAC) and the 35 mM K+-stimulated, Ca2+-dependent release of norepinephrine (NE), dopamine (DA), serotonin (5-HT), gamma-aminobutyric acid (GABA), glutamate, and aspartate from cerebral cortical slices of the alcohol-preferring P line of rats and stock Wistar rats were studied. The K+-stimulated, Ca2+-dependent release of GABA for the P rats was 35% lower, while the release of glutamate was almost twice that of the stock animals. The release of the other compounds was similar for the two groups. Addition of 250 mg/100 ml ethanol to the superfusion media did not alter the release of NE, DA, and 5-HT nor the efflux of DOPAC from cortical slices of either group of rats. However, the K+-stimulated, Ca2+-dependent release of GABA, glutamate, and aspartate was significantly enhanced by ethanol for both the P and stock group of rats. These in vitro data do not support a direct action of ethanol on DA, NE, and 5-HT release or on DOPAC efflux, but suggest a direct action on the transmitter release process for GABA, glutamate, and aspartate in the cerebral cortex.