The effects of ethanol (1-80 mM) on GABA-activated Cl- current (IGABA) were studied in cultured mammalian hippocampal and cortical neurons. Patch-clamp recordings revealed that ethanol potentiated the Cl- current in a concentration-dependent manner (1-40 mM) in the majority of the cells studied. No higher degree of potentiation was found by increasing the concentration of ethanol to 80 mM. This study demonstrates that ethanol can potentiate IGABA in mammalian central neurons.