OBJECTIVE: In St. Petersburg, Russia, we sought to describe the characteristics of active high-risk injection drug users (IDUs) to evaluate the associations between behavioral and demographic characteristics and HIV-1 infection and to describe 3 discrete recruitment methods. METHODS: Active high-risk IDUs were recruited in 3 ways: through street outreach, at facilities serving IDUs, and by network-based chain referral. Recruits were screened, counseled, and tested for HIV-1. Sociodemographic and behavioral data were collected. HIV-1 prevalence was analyzed as a function of sociodemographic and behavioral variables. RESULTS: During the 10-month recruitment period, data from 900 participants were collected: median age was 24 years, and in the previous month, 96% used heroin and 75% shared needles with others. The baseline HIV prevalence was 30% (95% confidence interval [CI]: 27 to 33). Recruitment through social networks was the most productive strategy. HIV-positive individuals were younger, but none of the other sociodemographic or behavioral characteristics differed significantly by HIV status. CONCLUSIONS: The estimated HIV prevalence of 30% places St. Petersburg among the worst IDU-concentrated epidemics in Europe. Recruitment through network-based chain referral is a useful method for recruiting active IDUs. Sociodemographic and behavioral links to prevalent HIV infection remain to be elucidated.