The two major catagories of diagnostic methods for Helicobacter pylori are invasive tests, or those that require endoscopy, and noninvasive, or nonendoscopic, tests. Diagnostic tests that use endoscopy include rapid urease tests, histology, and culture. Tests for which esophagogastroduodenoscopy is not necessary include various methods of antibody detection and carbon-labeled urea breath tests. Most tests are accurate, although none works perfectly and no gold standard for diagnosis exists. This article reviews the diagnostic methods available to establish H. pylori infection status and identifies some common mistakes made in testing. The costs associated with H. pylori diagnosis are evaluated and some cost-effective approaches to testing are suggested. Finally, the article offers some guidelines on choosing the appropriate diagnostic test in different clinical situations to determine the H. pylori infection status.