The investigators propose to examine the role of social context and social influence on syphilis transmission in Baltimore. Currently, Baltimore has the Nation's highest rates for newly acquired primary and secondary syphilis. The goals of this study are, first, to examine the social context of syphilis risk through the assessment of social and sexual network characteristics. In collaboration with he Baltimore City Health Department (BCHD), the investigators will recruit between 400 and 1200 patients who present to the BCHD Sexually transmitted Diseases (STD) clinics for evaluation and treatment of primary and/or secondary stage syphilis. The investigators will collect specimens from these patients' syphilis lesions for restriction fragment length polymorphism (RFLP) analysis, and conduct social and sexual network interviews with these syphilis patients and their social/sexual network members. Using Geographic Information System (GIS), the investigators will map the social and sexual networks. This will allow us to track and compare possible syphilis transmission through both network types and to examine social structural factors, especially drug use, which may be associated with disease transmission and risk behaviors. Social context data will be confirmed by biologically-based strain typing. The investigators propose to apply the RFLP technique in collaboration with Dr. Sheila Lukehart at the University of Washington to determine the prevalence of and factors associated with genetic clustering of syphilis in Baltimore over time. The investigators will determine if different RFLP profiles exist m Baltimore, use GIS to plot their spatial distribution and evaluate the relationship of social networks to clusters of infections. This will be the first time that a biological marker of transmission will serve to validate epidemiological defined transmission groups and thus improve our ability to delineate the sexual, social and personal network characteristics associated with syphilis transmission. The investigators are currently funded to examine the role of social context on gonorrhea transmission. As a second goal of this study will be to compare the social context of syphilis risk to that of gonorrhea risk and to determine and compare the role of drug use and other social factors in the social context of both sexually transmitted diseases. Thus, the investigators propose to compare the efficacy of detecting early infectious (primary and secondary stage) syphilis cases by interviewing and screening social network members of early syphilis index cases compared to that of standard sexual partner notification techniques. The proposed project seeks five years of support to map, analyze and compare syphilis cases within social and sexual networks. Data collected in this proposal data may be applied to modify current methods of syphilis contact tracing and develop more effective future preventive and intervention strategies.