This research will be part of the Center for Disease Control and Prevention's HIV national behavioral surveillance and will be implemented in Atlanta, Georgia. As part of this endeavor, a total of 1500 adults, who are at heightened risk for HIV infection, will be recruited to participate over the course of three years. Trained interviewers will assess HIV-related behaviors and HIV infection status in an anonymous, face-to-face interview and with a voluntary HIV test. Formative ethnographic assessments will be conducted in each of the three years to gather information about the particular populations and the communities in which they reside and interact. In the first year, 500 men who have sex with men (MSM) will be recruited from venues in the community where MSM frequent. In the second year, 500 injection drug users (IDUs) will be recruited using respondent driven sampling (RDS) methodology. In the third year, 500 heterosexuals living in or frequenting areas located in the Atlanta, GA Metropolitan Statistical Area will be recruited using RDS. These data will be used to guide HIV prevention program activities, evaluate current HIV prevention programs and monitor HIV related behavioral trends. ? ? ?