The diagnosis of peptic ulcer must be precise and based on both endoscopic examination (in the case of gastric ulcer to differentiate between benign or malign ulcers), and on bioptic examination. Peptic ulcer is pathogenetically associated with H. pylori. A small group of patients with duodenal ulcers and without H. pylori or without an other known cause (NSAID, etc.) is a poorly defined sub-group of patients. H. pylori has an important role in the pathogenesis of gastritis and bulbitis. Both states are involved in the pathogenesis of peptic ulcer. If H. pylori is eradicated, inflammatory changes of the gastric and duodenal mucosa recede and the recurrence of peptic ulcer decreases to a minimal size. For estimation of H. pylori, several invasive and non-invasive techniques are used. Among invasive methods most used in peptic ulcers, a combination of the rapid urease test and histology seems to be the most important. Among non-invasive methods, the breath tests are the most reliable. The treatment is focused on the eradication of H. pylori (no H. pylori is found one month or more after completed therapy). Of the eradication regimens, the triple therapy with proton pump inhibitors, claritromycin and metronidazole or amoxicillin are most effective. If this therapy fails, quadrutherapy (triple therapy combined with colloid bismuth subcitrate) may be successful. The precise diagnosis of peptic ulcer and H. pylori infection is a basic prerequisite for rational therapy of peptic ulcer disease and its relapses.