Finding the causal chain.

Traditional sampling methods are unsuitable for determining the levels of human immunodeficiency virus type I infection and related behavioral risk factors among young men who have sex with men. Most surveys of this hard-to-reach population have used nonprobability samples of young men in clinical or public settings. While these studies have revealed high rates of HIV infection and risk behaviors, their findings are not generalizable to broader populations of young men who have sex with men. To better understand the epidemiology of HIV within this population, the Centers for Disease Control and Prevention, in collaboration with state and local health departments, has developed a venue-based probability survey of young men who have sex with men. Conducted in seven metropolitan areas in the United States, the Young Men's Survey combines outreach techniques with standard methods of sample surveys to enumerate, sample, and estimate prevalence outcomes of a population of young men who frequent public venues and who have sex with other men. Venues where young men who have sex with men are sampled include dance clubs, bars, and street locations. At sampled venues, young men are enumerated, consecutively approached, and offered enrollment if they are determined eligible. Young men who agree to participate in the Young Men's Survey are interviewed, counseled, and tested for human immunodeficiency virus, hepatitis B, and syphilis in vans parked near sampled venues. The Young Men's Survey provides data on the locations and times at which demographic and behavioral subgroups of young men who have sex with men may be targeted for prevention activities. Behaviors and psychosocial factors associated with human immunodeficiency virus infection can be used to design culturally relevant and age-specific prevention activities for young men who have sex with men.