Background:The impairment of gastric acid barrier caused byHelicobacter pylori(H. pylori) at the onset of infection may predispose to small bowel bacterial overgrowth, which could contribute to persistent diarrhea.Methods:Using the13C-urea breath test, we determined the prevalence ofH. pyloriinfection in 123 Nicaraguan children from Tipitapa, aged 1 to 65 months, from a low socioeconomic background.Results:The overall prevalence ofH. pyloriinfection was 77.2% (95/123). The prevalence varied with age and was significantly (p < 0.001) higher in infants ≤12 months than in children aged 13-65 months, 91% (57/63) as against 63% (38/60).H. pyloriinfection was present in 44 of 59 (75%) children suffering from persistent diarrhea compared with 51 of 64 (80%) age-matched asymptomatic controls. In the diarrheal group, 20 of 59 (34%) children presented with malnutrition, and 16 (80%) of them showedH. pyloriinfection. In the control group, 20 of 64 (31%) were malnourished, and 14 (70%) of them showedH. pyloriinfection.Conclusions:In Nicaragua,H. pyloriis acquired in early infancy. The high prevalence among children in the first 12 months of life and the lower infection rate between 1 and 5 years of age suggest a loss or clearance of infection, also an occasional finding in adults.H. pyloriinfection appears to be not a risk factor for persistent diarrhea or malnutrition in Nicaraguan children.