Recognition of Helicobacter pylori (Hp) as the major cause of peptic ulcer disease has profoundly changed treatment and prognosis of this disease. The diagnostic tests are invasive (i.e. via the endoscopy) or non-invasive. The invasive tests are: urease test, histology, culture and PCR. Non invasive tests are: breath test, serology and Hp-antigens in faeces. The performance of the tests are almost similar. Sensitivities and specificities usually are > 90%, however the sensitivities and specificities of serological tests may be lower. Choice of diagnostic test depends on the clinical situation, sensitivity and specificity of test and the prevalence of Hp. Patients who should be examined for Hp: 1. The peptic ulcer patient who has used ASA/NSAID (urease test). 2. MALT-lymphoma, (histology). 3: The young (< 45 years) dyspeptic patient with no alarm symptoms and not taking NSAID/ASA (breath test). 4. Recurrence of upper dyspepsia after former eradication of Hp in peptic ulcer patients (if malignancy is not suspected breath test is first choice). 5. Verification of Hp eradication is necessary only in patients with MALT-lymphoma (histology) or patients with complicated peptic ulcer. Breath test will be the first choice in patients with complicated peptic ulcer when endoscopy is not performed. When endoscopy is performed, the urease test is the first choice. Diagnosis of Hp status not indicated: 1. There is no documentation that Hp eradication is of benefit in patients with non organic dyspepsia. Therefore, there is no indication for diagnosis of Hp. 2. Although there is some association between Hp positivity and chronic active gastritis and carcinoma of the stomach, there is at present no indication for diagnosis of Hp, as treatment of the infection has not proved effective in reversing atrophy or dysplasia. 3. The relationship between Hp and ASA/NSAIDs in peptic ulcer disease is far from clear. There is no indication for diagnosis and treatment of the infection prior to treatment with these medications. 4. For patients treated with longterm proton pump inhibitors there is no indication for diagnosis and treatment.