Helicobacter pylori has been extensively studied and proven to be the main cause of chronic gastritis and peptic ulcer in the HIV-negative population. Patients with chronic active gastritis have evidence of H pylori infection in over 90% of cases and in 70-100% of those with peptic ulcer disease. However, the reason for low incidence of H pylori infection in HIV-positive patients was still not very clear. A study examining this issue was recently reported in the November 7 issue of the World Journal of Gastroenterology because of its great significance for AIDS-related diseases.