Background and Goal: In areas with persistent syphilis, to characterize persons at higher risk for transmitting syphilis. Study Design: Cohort study. Structured interviews of persons with early syphilis from four research centers were linked to outcomes of partner tracing. Results: Of 743 persons with syphilis, 229 (31%) reported two or more partners in the previous month, and 57 (8%) received money or drugs for sex in the previous three months. Persons with at least one partner at an earlier stage of syphilis than themselves were defined as transmitters; 63 (8.5%) of persons with early syphilis met this definition. Having concurrent partners (two or more in one week in the last month) was independently associated with being a transmitter. Conclusion: Sexual network/behavioral characteristics of syphilis patients and their partners, such as concurrency, can help identify persons at higher risk for transmitting syphilis who should receive emphasis in disease prevention activities.