Impressive advancements in our understanding of the mechanisms of diarrhea production and of the epidemiologic importance of these "classical" bacterial enteropathogens have been accomplished, but many areas are in need of further exploration. The recent development of gene probes and enzyme-linked immunosorbent assays for the identification of EPEC, ETEC and EIEC will enhance immeasurably the ability to carry out large scale epidemiologic studies which are still needed to clarify the global importance of these pathogens in infantile diarrhea. For some of these organisms pathogenic mechanisms remain incompletely understood and the role of antibiotics is not well-established. The delineation of virulence factors, immunity and the construction of attenuated strains through DNA recombination technology are bringing the worthy goal of prevention through vaccination into view. These advances should not, however, detract attention from the primary reason that these bacteria continue to be a major cause of childhood morbidity and mortality in the developing world, which is lack of adequate sanitation. Efforts to provide clean water, safe waste disposal and hygiene education need to proceed in conjunction with development of vaccines.