Although Helicobacter pylori is considered to be relatively homogeneous at the phenotypic level, our aim was to describe its antigenic heterogeneity and to examine differences in host response. Whole-cell lysates of H. pylori strains originally isolated from persons from Africa, the People's Republic of China, Japan, Peru, Thailand, or the United States or from monkeys were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoblots were performed by using sera from H. pylori-infected persons from different areas of the world and rabbit immune sera against H. pylori antigens. Specific H. pylori antibody responses in persons from the United States and the People's Republic of China were analyzed by enzyme-linked immunosorbent assay with antigens prepared from U.S. or Chinese strains. Despite diverse origins, the strains showed conserved major bands of 84, 60, 56, 31, and 25 kDa. Although there were clear differences in minor bands, there was no obvious geographic pattern. The anti-CagA serum recognized 120- to 140-kDa bands in cagA+ strains from around the world. Although antigenic preparations from individual U.S. or Chinese strains were not optimally sensitive for serologic detection of infection in the heterologous country, use of pools of strains largely overcame this phenomenon. We conclude that conserved H. pylori antigens exist and are recognized by sera from persons from many parts of the world. The heterogeneity of H. pylori antigens and the serological responses of infected hosts is not fully explained by geographic differences. Use of pools may allow development of antigens for serologic testing in any country.