Prevention Science, Vol. 4, No. 3, September 2003 ( C  2003) Reductions in HIV Risk Among Runaway Youth Mary Jane Rotheram-Borus, 1,5 Juwon Song, 1 Marya Gwadz, 2 Martha Lee, 1 Ronan Van Rossem, 3 and Cheryl Koopman 4 Runaway youth are 6–12 times more likely to become infected with HIV than other youth. Using a quasi-experimental design, the efficacy of an HIV prevention program was evaluated over 2 years among 2 groups of runaways: (1) those at 2 shelters who received Street Smart, an intensive HIV intervention program, and (2) youth at 2 control shelters. Street Smart provided youth with access to health care and condoms and delivered a 10-session skill-focused preven- tion program based on social learning theory to youth. Prior to analysis of the intervention’s outcomes, propensity scores were used to identify comparable subgroups of youth in the intervention (n = 101) and control conditions (n = 86). Compared to females in the control condition, females in the intervention condition significantly reduced their unprotected sexual acts at 2 years and alcohol use, marijuana use, and the number of drugs used over 12 months. Male adolescents in the intervention condition showed significant reductions in marijuana use over 6 months compared to control youth. Adolescent HIV prevention programs must proactively identify mechanisms for maintaining behavior change over the long-term, and innovative research designs are needed to allow examination of agency-level interventions. KEY WORDS: HIV; adolescents; minority youth; runaway; homeless. Prevention of HIV among adolescents is a crit- ical national health priority (National Institute of Health [NIH] Consensus Development Conference Panel, 2000). Runaway youth are a subgroup at par- ticularly high risk of HIV (Rotheram-Borus et al., 1991a). In America’s inner cities, homeless youth are estimated to have a median seroprevalence rate of 2.3% (Allen et al., 1994) compared to 0.2–0.4% for 1 Department of Psychiatry, University of California, Los Angeles, California. 2 Institute for AIDS Research, National Development and Re- search Institutes, New York. 3 Department of Child and Adolescent Studies, Utrecht University, Utrecht, the Netherlands. 4 Department of Psychiatry and Behavioral Sciences, Stanford Uni- versity School of Medicine, Standford, California. 5 Correspondence should be directed to Mary Jane Rotheram- Borus, PhD, Division of Social and Community Psychiatry, De- partment of Psychiatry, University of California, Los Angeles, 10920 Wilshire Blvd., Suite 350, Los Angeles, California 90024; e-mail: rotheram@ucla.edu. adolescents in medical clinics and Job Corps (Quinn et al., 1988; St. Louis et al., 1989; Sweeney et al., 1995). In New York City, a major AIDS epicenter (Centers for Disease Control and Prevention, 2000), HIV sero- prevalence rises to 9.8% among 20-year-old homeless young people (Stricof et al., 1991). On the basis of an- nual national estimates of 733,000 to 1.2 million run- away youth, we estimate that 16,859–27,600 runaway youth in the United States are currently seropositive for HIV. These numbers highlight the importance of implementing effective HIV prevention programs for these youth. The goal of this study is to evaluate the efficacy over 2 years of Street Smart, an HIV preven- tion program delivered in runaway shelters. Both sexual and substance use behaviors must be targeted in an intervention, because both have been linked to HIV infection (Celentano et al., 1998; NIH Consensus Development Conference Panel, 2000) and are common among homeless youth. A history of sexual abuse, bartering sex for drugs or money, early initiation of sexual intercourse, frequent changes in 173 1389-4986/03/0900-0173/1 C  2003 Society for Prevention Research