Only one of 167 separate isolates of enteropathogenic Escherichia coli (EEC) was shown to produce enterotoxin, and none of the 167 isolates were invasive. Clinical features of 123 hospitalized children with EEC were compared with those of 917 infants with nonbacterial gastroenteritis and 145 infants infected with Shigella. The average duration of diarrhea (five or more stools per day) in hospitalized children with EEC, nonbacterial gastroenteritis, Shigella flexneri, and Shigella sonnei was 4.6, 2.4, 5.1, and 2.5 days, respectively. The average duration of fever in these four groups was 1.4, 1.2, 2.1, and 1.2 days, respectively. The difference in duration of diarrhea between children with EEC and those with nonbacterial gastroenteritis was significant (P less than 0.001), even when age and rural/urban origin were controlled by analysis of variance. Nevertheless, the EEC group tended to be younger and to have a higher proportion of infants of rural origin. Although it appears that EEC serotypes rarely identify invasive or enterotoxin-producing organisms, clinical features of infants with EEC-associated gastroenteritis suggest that these infants may represent a distinctive and clinically important group with gastroenteritis of greater severity than nonbacterial gastroenteritis.