Helicobacter pylori infection is common. The World Health Organization estimates that about 70% of people in developing countries and 30% in developed countries are infected with this bacterium. The infection spreads through personal contacts via an oral-oral, gastro-oral and faecal-oral route of transmission. Helicobacter pylori infection is asymptomatic in 80–90% of cases. Both invasive and non-invasive methods are used in the diagnosis of this infection. The choice of the method depends on the current clinical condition and the necessity to perform endoscopy of the upper gastrointestinal tract. Since the incidence and prevalence of Helicobacter pylori infection are high, H. pylori detection tests should be performed only when eradication therapy is planned. According to the guidelines of the Working Group of the Polish Society of Gastroenterology, eradication treatment involves a multidrug therapy with proton pump inhibitors, antibiotics and bismuth citrate. All of these drugs should be used for a period of 10–14 days. Clarithromycin should not be used as the first choice treatment because of increasing resistance in Poland. A breath test is an optimal way to evaluate the effectiveness of the antibacterial therapy but is rarely performed due to high price and low availability. Serology tests are available and cheap, but are not suitable to assess the efficacy of eradication. Helicobacter pylori antigen detection in stool is therefore important in the diagnosis. The test is not very expensive, available and characterised by very high sensitivity and specificity of up to 90%.