Helicobacter pylori causes chronic gastritis worldwide and it is the most important single factor in peptic ulcer disease. Up to half of H. pylori infected individuals develop atrophic gastritis over years and decades. H. pylori infection has also been classified as a class I carcinogen in human gastric cancer. Most infections are obtained in childhood, in Finland mainly before the age of 7 years but the exact transmission routes are not known. The infection shows an age-dependent pattern, the infection being rare among children but gradually becoming more prevalent among older age groups. As new infections are few in adults and the infection only rarely disappears without effective anti-microbial therapy, the occurrence of the infection in the old actually reflects the prevalence of the infection in their childhood. In developed countries, such as Finland, a rapid decline of H. pylori prevalence rate has been demonstrated. In order to speed up this natural decline of the infection, a unique population based 'screen and treat' project was started in Vammala, a semiurban south-western community in Finland. In this survey, young inhabitants were offered diagnosis and treatment for H. pylori.