Radioimmunoprecipitation (RIP) and Western blot analyses with specific anti-Treponema pallidum subsp. pallidum monoclonal antibodies were used to identify antigens with apparent masses of 102, 84, 54, 53, 52, 47, 32, 29, and 24 kilodaltons (kDa). Cross-reactivity of these antibodies with T. pallidum subsp. pertenue antigens and lack of cross-reactivity with T. phagedenis biotype Reiter, T. vincentii, T. refringens, T. scoliodontum, and T. denticola were also demonstrated by RIP and Western blot analyses. Reactivities in the T. pallidum immobilization test, along with the RIP of lactoperoxidase-catalyzed iodination products, suggested that the identified antigens were surface associated. The abundance and surface association of the 47- and 84-kDa antigens were supported by reactivity in the microhemagglutination test for T. pallidum and by strong reactivity of monoclonal antibodies upon indirect immunofluorescence assays with rabbit-cultivated T. pallidum subsp. pallidum, respectively, but not with T. phagedenis biotype Reiter. Anti-47-kDa and anti-84-kDa monoclonal antibodies were also reactive in indirect immunofluorescence assays using treponemes found in dark-field-positive smears of human genital ulcers.