Objective: Prevalence of asymptomatic Helicobacter pylori infection is very high in infants and children in developing countries. 13C urea breath test (UBT) is a reliable non-invasive diagnostic test for H. pylori infection in children that avoids invasive endoscopy. We compared a newly introduced H. pylori stool antigen test (with a high sensitivity and specificity in symptomatic children) with UBT in asymptomatic children mostly 1-5 years old, from a population with a high prevalence of infection. Method: Eighty six asymptomatic children (42 boys and 44 girls) were tested for H. pylori infection using the UBT and a stool antigen test (HpSA) based on a sandwich enzyme immunoassay for antigen detection. Results: Forty five of the eighty-six (52.3%) children tested positive for H. pylori using the breath test. In 34 of these forty-five children, H. pylori antigen was detected in stool (sensitivity = 75.6%, 95% CI = 63 to 88%). Of the 50 of 86 (58%) children positive by HpSA test, 34 were positive for breath test. Of the 41 children with negative UBT test 25 were negative for stool antigen test (specificity = 61%, 95% CI = 46 to 76%). Conclusion: The sensitivity and specificity of the new stool antigen test are lower in asymptomatic children with high H. pylori prevalence rate compared to those reported for children with gastrointestinal symptoms. Its usefulness is limited for diagnosis in an asymptomatic child with H. pylori infection. © 2005 Lippincott Williams & Wilkins.