The purpose of this study was to determine the effects of repeated colloidal bismuth subcitrate administration on the cellular populations of the fundic region of the rat stomach and to investigate the effect of such treatment, after initial ethanol damage, on the gastric response to a second challenge by ethanol. The administration of 240 mg of colloidal bismuth subcitrate per kilogram body weight, at 12 hour intervals, for 14 days, resulted in an increase in the density of the mucosal epithelial cells, but a decreased rate of epithelial cell division in the neck region. Comparison with placebo treated animals showed that the repeated administration of colloidal bismuth subcitrate after an initial ethanol challenge, decreased the degree of damage induced by a second ethanol challenge, enhanced the rate of tissue repair and prevented the establishment of persistent erosions.