Ever since 1983 when Marshall & Warren succeeded in cultivating Helicobacter pylori (HP) (previously known as Campylobacter pylori) a high incidence thereof has been demonstrated in patients with ulcers and non-ulcerous dyspepsia. Helicobacter pylori is easily diagnosed via microscopy, cultivation and serological tests. The bacterium may be treated with antibiotics or the ulcer drug bismuth subcitrate (De-Nol). The pathogenetic role of HP is not clear. Some studies have shown a lower recurrence rate of duodenal ulcers after treatment addressed to Helicobacter pylori with the ulcer drug De-Nol, which suggests that HP plays a role in the onset of recurrence in cases of ulcus duodeni.