Although oral electrolyte solutions (OES)replenish salts and water lost during diarrhea, presentformulations do not address disturbances of the normalintestinal microbiota. Therefore, we evaluated the efficacy of an OES with and withoutfructooligosaccharide (FOS) for treatment of pigs withacute secretory diarrhea induced by cholera toxin.Before, during, and after diarrhea, bacteriologicevaluation was made of contents collected from the midsmall intestine, cecum, and distal colon and mucosascraped from the mid small intestine. Diarrhea causedsignificant declines in total bacterial counts ofcontents from all three regions, with less of an impacton bacteria associated with the mucosa. Although totalbacterial counts recovered within 24 hr, regardless oftreatment, densities of Enterobacteriaceae were higher in pigs treated with OES whereas thosereceiving FOS had more lactobacilli. Our results showthat secretory diarrhea disturbs the normal densitiesand relative species abundance of the microbiota, with the influences more pronounced forcontents relative to the mucosa, and that adding FOS toOES accelerates the recovery of bacteria perceived asbeneficial while potentially slowing the recovery of pathogenic forms.