From January 1983 through January 1985, 88 cases of early adult syphilis and five cases of congenital syphilis were identified among residents of a southwestern Indian reservation. The male-to-female ratio of primary and secondary syphilis cases was 1.7: 1; over 90 per cent of women were of childbearing age. Using community health workers to determine the social circles of infected persons was effective in identifying persons at risk; treatment of partners of infected persons prior to development of seroreactivity contributed to the successful control of this outbreak.