Helicobacter pylori has been the subject of intense investigation since its culture from a gastric biopsy in 1982.From the beginning, this gram-negative bacterium has provoked the interest of bacteriologists, gastroenterologists,infectious disease specialists, cancer biologists, epidemiologists, pathologists, and pharmaceutical scientists.Pathologists were among the first groups of scientists to reevaluate their data in the context of the newlydiscovered bacterial etiological agent. Chronic inflammation elicited by the bacterium provided the missing linkin the progression to gastric carcinoma; accordingly, H. pylori was named as a class 1 carcinogen by the WorldHealth Organization. Two key papers published in 1991 in the Journal of the National Cancer Institute reporteda positive association between gastric cancer and H. pylori infection. This fact provided a strong rationale to treatall who tested positive for H. pylori. Antibiotic regimens have been largely successful, but some agents such asmetronidazole and clarithromycin have been rendered ineffective in several countries and geographical areas ofthe United States by the emergence of strains resistant to these compounds. Although there was some skepticisminitially, within few years numerous research groups verified the association of H.pylori with gastric carcinoma.Host related factors for the development of disease can indicate genetic susceptibility (or resistance) or acquiredinfluences, which may stimulate defenses of the host against environmental carcinogens like H.pylori. The presentarticle is a mini-review of the history and epidemiology of the bacterium and its suggested association with thedevelopment and progression of gastric cancer.