Inhabitants of a remote Panamanian village were examined for clinical and serological evidence of pinta infection. Of 104 persons examined, 21 (20%) had clinical evidence of active or inactive pinta, and 54 (52%) were seropositive. Sera were evaluated for antibody to individual Treponema pallidum antigens. Sera from all four patients with active pinta contained antibody to the 47-48 kilodalton major antigen; the intensity of reactivity and the number of antigens recognized increased with age and, presumably, duration of infection. Sera from six children with inactive pinta reacted strongly with multiple T. pallidum antigens, whereas adults with inactive pinta had less intense reactivity against fewer molecules. Seronegative controls demonstrated only weak reactivity to fewer than five molecules. The development of antibody reactivity to the full spectrum of T. pallidum antigens during the course of infection demonstrates the high degree of antigenic relatedness of T. pallidum and Treponema carateum and is similar to the development of humoral responsiveness during syphilis infection.