A study of the incidence of antibiotic resistant fecal Escherichia coli in children from an urban ghetto and a private practice indicated that a higher proportion of resistant E coli (65%) was obtained from the ghetto population compared to 51% of private patients. Ampicillin resistance was most common in both populations but significantly greater in the ghetto (51% vs 31%). Transmissible resistance factors were demonstrated in 73% of the resistant strains from ghetto children and 25% from children of upper socioeconomic background.