The effect of ethanol (EtOH) on ion current mediated by recombinant alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)/kainate (KA) receptors was examined in transfected human embryonic kidney 293 cells using whole-cell recording. Inhibition of KA-activated current was observed in the presence of intoxicating EtOH concentrations. The potency with which EtOH inhibited current was similar for receptors formed by different subunits or subunit combinations. EtOH also inhibited KA-activated current in cultured neurons from fetal rat cortex. However, the potency of EtOH inhibition in cortical neurons was lower than that observed in 293 cells expressing recombinant receptors. The properties of receptors in cultured neurons, other than EtOH sensitivity, were similar to those displayed by recombinant AMPA/KA receptors. These observations indicate that some forms of non-NMDA ionotropic glutamate receptors have relatively high EtOH sensitivity. These receptors appear to differ in some respect from AMPA/kainate receptors expressed endogenously in cortical neurons.