OBJECTIVE: Epidemiological data indicate that females develop alcohol-induced liver disease (ALD) more rapidly and more severely than males. Though the contribution of gut-derived endotoxin to the onset and development of ALD suggests the loss of epithelial cell viability that results in impaired intestinal function due to alcohol exposure, the additional effects of female sex hormones on intestinal cell viability is not known. The aim of this study was to examine the influence of estradiol on the intestinal cell death induced by acute and low concentrations of ethanol in an in vitro system. MATERIAL AND METHODS: Human intestinal epithelial Caco-2 cells were incubated with 0, 5, and 10% ethanol for 3 h. Estradiol stimulation, concentration of 3, 30, and 300 pg/ml occurred in the presence or absence of 10% ethanol for 2 h. Phosphatidylserine (PS) externalization, caspase-mediated cytokeratin 18 (CK18) cleavage, and DNA fragmentation were quantified using flow cytometry. RESULTS: Treatment with 10% ethanol markedly induced PS externalization, caspase activation, and DNA fragmentation after 2 h incubation. Whereas estradiol itself did not affect cell viability, physiological concentrations of estradiol enhanced PS externalization and DNA fragmentation induced by 10% ethanol, and these were remarkable at 300 pg/ml estradiol. CONCLUSIONS: Ethanol-induced apoptosis was potentiated by physiological concentrations of estradiol, especially at the higher level which is found only in females. Our data suggest that enhanced ethanol-induced intestinal epithelial cell apoptosis in the presence of estradiol could cause greater intestinal permeability, which allows endotoxin to enter the circulation and eventually results in more severe ALD in females.