Significance We have continued our studies of Helicobactor pylori infection in rhesus macaques using the urea breath test (the application of which we have adapted to non-human primates), gastric biopsy techniques (including culture, histology, and PCR), and drug treatment of infected animals. Objectives Our objectives continue to revolve around a better understanding of the natural history of infection with H pylori in order to facilitate treatment and prevention of this disease in humans where it can cause gastric ulcers and neoplasia. Our most significant recent accomplishments include the development of a sensitive and specific serologic assay for H pylori in rhesus macaques, and the finding that the urea breath test, a test receiving increasing application in humans for the diagnosis of H pylori infection, is not sensitive for the detection of early (experimental) infection. Future Directions Future goals include identification of a human isolate of H pylori which will infect rhesus macaques in order to improve our primate model and elucidation of the mechanism of transfer of this infection among animals. KEYWORDS Helicobactor pylori, immunization