Epidemiological studies indicate a relationship between alcohol consumption and esophageal epithelial disease. We therefore sought the contribution of the direct effects of ethanol on esophageal epithelial structure and (transport and barrier) function. Epithelium from the rabbit was mounted in Ussing chambers and exposed luminally for 1 h to 1-40% ethanol. At concentrations of 1-5% potential difference (PD) increased, and at 10-40% PD decreased. The increase in PD with 1-5% ethanol was accompanied by an increase in short-circuit current (I_sc), and this increase in I_sc could be blocked by ouabain pretreatment. The decrease in PD with 10-40% ethanol was associated with a decrease in electrical resistance (R), and this decrease in R was paralleled by an increase in transepithelial [¹⁴C]mannitol flux. Reversibility of these changes was limited at ethanol concentrations 10%, and these were associated morphologically by patchy or diffuse tissue edema. Moreover, as with ethanol exposure in vitro, exposure in vivo produced dose-dependent changes in PD, I_sc, R, and morphology. These observations indicate that exposure to ethanol in concentrations and under conditions reflecting alcohol consumption in humans can alter and impair esophageal epithelial transport and barrier functions. Such impairments are likely to contribute to the observed increase in risk of esophageal disease with regular consumption of alcoholic beverages.