Worldwide, gastric cancer is the second most frequent cancer and the second leading cause of death from cancer. Since the discovery of Helicobacter pylori in 1982 by Marshall and Warren, an association between the bacterium and gastric cancer has been suspected. Ten years ago, several case–control studies based on enzyme-linked immunosorbent assays (ELISAs) of stored serum found an association between H. pylori and cancer, but as defined by an odds ratio it was somewhat weak. These initial reports could attribute only 60 percent of cases of gastric cancer to H. pylori infection.¹ Although the World Health Organization and the International . . .