This paper reviews current diagnostic techniques for Helicobacter pylori infection and critically questions their value under different diagnostic circumstances. As long as we do not have general treatment recommendations for H. pylori infection, endoscopy is still the basis for primary diagnosis because it assesses therapy indications. In addition, histology characterizes the gastroduodenal lesions observed and may reveal malignant diseases. New rapid urease tests from the biopsies are inexpensive, simple, and quick giving results reliably within 1 h. Culturing H. pylori from gastric samples after therapy failure and testing the strains for antimicrobial susceptibility is becoming increasingly important with higher prevalence of drug resistances. Nonendoscopic tests are more convenient to the patient. Serological tests inexpensively detect circulating IgG or IgA antibodies. However, inspite of the cost attractiveness, serology might be problematic in indicating present H. pylori infection. The tests of choice for noninvasive monitoring therapy success or failure are the 13C-urea breath test and the faecal antigen immunoassay. Both tests are also of value for first diagnosis in children when endoscopy is not indicated. In the future, serological detection of virulence factors and polymerase chain reaction with molecular fingerprinting might help to identify H. pylori strains with high pathogenicity or antibiotic resistance.