Field follow-up to locate and treat partners of patients with syphilis and gonorrhea is standard procedure in the United States. The present study utilized 12,732 heterosexual index patients with gonococcal infection, chlamydial infection, and related syndromes to evaluate the effectiveness of field follow-up over a 6-year period. Field follow-up located 82% of the 13,845 partners identified by the index patients. Of those partners who were located, 36% had a documented infection with either chlamydia or gonorrhea. An average of only 1.09 partners per index patient was named, however, indicating that all partners may not have been reported. The largest number of infected partners was located for all index patients with gonorrhea and for men with chlamydia. Contact tracing was also effective for women with chlamydia, although less so. Field follow-up, as conducted in this study, is effective in locating the partners who are reported by the index patients.