The International Agency for Research on Cancer (IARC) of the WHO has recognized a cause-effect relationship between Helicobacter pylori (Hp) infection and gastric cancer of such magnitude that the presence of this infection increases the risk of gastric cancer approximately four times. Gastric cancer is currently the second cause of mortality due to malignant neoplasms in Mexico City. This article explores the association between Hp infection and gastric cancer incidence through an epidemiological study including 109 gastric cancer patients and 177 hospital controls in Mexico City. The study estimates that, in the population studied, Hp infection was present in 87.2% of the cases, compared with 82.5% of the controls. The odds ratio of having gastric cancer if infected with Hp was 1.44 IC95% 0.7-2.8. In addition, it was calculated that with eradication of Hp infection in the general population, gastric cancer incidence would decrease by at least 26.6%. An improvement of the actual sanitary conditions along with the development of an effective vaccine for Hp infection and the existence of increasingly effective treatments to eradicate the bacteria are the necessary next step for populational prevention and control of gastric cancer.