Helicobacter pylori colonization was measured by [13C]-urea breath test in 198 Gambian infants and by fecal enzyme-linked immunosorbent assay in 52 of the 198 at ages 2, 5, and 12 months. By 12 months there was good concordance between tests; 33 of 44 (75%) test results were positive by enzyme-linked immunosorbent assay, and 29 of 44 (66%) test results were positive by urea breath test. H. pylori colonization is common among Gambian infants, and noninvasive tests can provide a reliable means of diagnosis.