Helicobacter pylori (H. pylori) infection can be diagnosed by invasive techniques requiring endoscopy and biopsy (histological examination, culture, polymerase chain reaction) and by noninvasive techniques (serology, urea breath test, urine or blood, detection of H. pylori antigen in stool specimen). At present, no single test can be absolutely relied upon to detect colonization by H. pylori, and a combination of two tests is recommended if feasible. The tests used should depend on the clinical circumstances, the likelihood ratio of positive and negative tests, the cost-effectiveness of the testing strategy, and the availability of the tests. Some clinical circumstances warrant invasive studies, principally patients with alarm symptoms (bleeding, weight loss, etc.) as well as older patients with new-onset dyspepsia. Endoscopy may also be advisable in patients who have failed eradication therapy and need culture and antimicrobial sensitivity testing to determine an appropriate regimen. Recent studies have also demonstrated that a strategy to 'test and treat' for H. pylori in uninvestigated, young (< 50 years), dyspeptic patients in primary care is safe and reduces the need for endoscopy. Indeed, a number of clinical guidelines recommend noninvasive testing followed by treatment of H. pylori for dyspeptic patients in primary care based on clinical and economic analyses.