Superficial chronic gastritis caused by Helicobacter pylori may lead potentially to the development of atrophic gastritis, a precursor of gastric carcinoma. Based on histological studies, the prevalence of Helicobacter pylori infection in gastric cancer patients, has been reported to vary widely from 38% to 100%. This positivity rate tends to be higher in patients with gastric cancer in early stage than in those with advanced malignant disease, probably, due to the relative mild atrophic and intestinal metaplastic changes of the surrounding gastric mucosa that occur in the former group. The prevalence of Helicobacter pylori infection is not related to the anatomical localization of cancer in the stomach. The inclusion of cases in advanced stages of disease and the examination of a few small-sized number of gastric specimens may explain the discrepant findings reported so far regarding the prevalence of Helicobacter pylori infection in patients with gastric cancer. We found a strong association between Helicobacter pylori infection and the occurrence of gastric carcinoma. Therefore, Helicobacter pylori may be an important carcinogenetic factor for the occurrence of malignant disease in the stomach. Cure of Helicobacter pylori infection may potentially reduce the incidence of gastric cancer.