Despite its clinical significance, relatively little is known about the components of Helicobacter pylori that allow it to colonize, persist, and elicit an inflammatory response within the host. Bacterial surface components frequently influence colonization and persistence of a pathogen, as well as the disease process (1 ). In the case of H. pylori , one macromolecular assembled protein component that is unequivocally located on the surface of the bacterium is the sheathed flagellum. Two other proteins that can be isolated in abundance from suspensions of H. pylori cells, but that are normally regarded as intracellular in other bacterial species, are urease and a GroEL analog, Hp60K (2 -6 ). Whether these large macromolecular assemblies are surface proteins on H. pylori or are released as a result of cellular lysis is uncertain. However, numerous other intracellular proteins can be readily isolated from culture supernatants after mild shearing and extraction procedures, and these released proteins have initially been incorrectly interpreted as representing surface proteins (7 -9 ).