The Sverdlovsk region is among the leaders in HIV prevalence in Russia. There are three groups vulnerable to HIV: people who inject drugs (PWID); men who have sex with men (MSM), and «sex workers» (SW). We assessed the potential of infection transmission to the general population, resulting from risky sexual practices, as exemplified by these three groups, and also analyzed the incidence of HIV, hepatitis C, and syphilis in these groups. An anonymous survey combined with testing of respondents for blood infection was carried out from June to October 2014 in Ekaterinburg. The study included 380 PWIDs, 387 MSM, and 250 SWs. According to the results of the study, HIV was detected in 65,3% of PWIDs, 5.2% of MSM, and 14.8% of SWs. PWID has the greatest potential for HIV transmission to the bridging population of their sexual partners due to the widespread non-use of condoms during sexual intercourse with non- PWIDs. SWs most often do not use condoms with regular and casual partners, while they adhere to use of condoms with commercial partners. Risky sexual practices are common among MSM, but this group is quite close, and sexual contacts outside the group are rare.