The epidemiologic significance of enteroaggregative Escherichia coli (EAggEC) as a diarrheal pathogen has only recently come under study. Although EAggEC has been associated with persistent diarrhea in infants in some developing countries, additional studies are clearly needed. Until now, the only means of identifying EAggEC strains has been the cumbersome HEp-2 cell adhesion assay. The isolation and cloning of a 1-kilobase fragment from the plasmid of EAggEC strain 17-2 is described. This probe is 89% sensitive and 99% specific for EAggEC identification. Thus, this probe should greatly facilitate epidemiologic studies assessing the importance of EAggEC as a diarrheal pathogen.