Although population-based studies have shown that children have the highest age-specific incidence of infection with the Shiga-like toxin-producing E. coli (SLTEC), these sporadic case series were not focused specifically on the pediatric age group. We undertook a prospective study to determine the frequency of detection of SLT in an exclusively pediatric population. The study design minimized ascertainment and referral bias by systematically defining the population by the presence of diarrheal symptoms rather than by specific diagnosis, previous submission of stool for culture, or referral to a diarrhea study. All children < 10 years of age hospitalized at a tertiary care pediatric hospital, irrespective of admission diagnosis, were surveyed prospectively at admission and for 2 days thereafter for the presence of defined diarrheal symptoms. From May 1, 1991, to April 30, 1992, 227 patients and 92 age- and season-matched controls were enrolled. Fecal SLT was detected in six (2.6%) patients, three of whom had E. coli O157:H7 organisms were isolated; SLT was not found in any of the controls. SLT was more commonly detected in children 2-10 years of age and in bloody stools. Salmonella was isolated in six (2.6%) cases, Shigella in five (2.2%), and Yersinia in three (1.3%); rotavirus was detected in 46 (20.3%). Two patients with SLT-associated diarrhea had hemolytic uremic syndrome (HUS), and four had hemorrhagic colitis. SLT-associated diarrhea occurred in the summer and fall months in contradistinction to that with rotavirus, which occurred in the winter and spring.(ABSTRACT TRUNCATED AT 250 WORDS)