Helicobacter pylori colonizes the stomach of half of humanity. The prevalence of this infection is higher among people of low socioeconomic status and from developing countries. In the absence of effective antibiotic treatment, the infection persists decades or even lifetime. The diagnosis of H. pylori can be made by invasive methods when biopsies are obtained: culture, histological examination, polymerase chain reaction or rapid urease test. Non-invasive methods have been developed, including the urea breath test, a test of high reliability, particularly suitable for post-treatment monitoring, but also the fecal antigen test, as well as the detection of antibodies in the serum. Culture is important for studying sensitivity to antibiotics, in particular clarithromycin and fluoroquinolones. The present paper presents the main diagnostic tests available today for a modern diagnosis of this bacterial infection discovered over thirty years ago.