Youth in urban areas with a history of running away from home often have special needs. Importantly, risk factors for HIV/AIDS might be associated with such a history. We assessed the association between having a history of running away from home and the occurrence of HIV infection and risk behavior among young men who have sex with men (YMSM), aged 15-22 years. A cross-sectional epidemiologic and behavioral survey was conducted between 1995 and 1996 in Miami, Florida, as part of a national Young Men's Survey. Of 488 YMSM, the prevalence of HIV infection among those with a history of running away from home was 10.5% (adjusted odds ratio=3.4; 95% CI 1.5-7.8). YMSM who had ever run away were more likely to be HIV infected, be out of school, and have ever had vaginal or anal sex with females, been forced to have sex, injected drugs, and used needles for self-tattooing or body piercing. The prevalence of HIV infection and associated risk behaviors among runaways was high, highlighting the ongoing need for prevention and social support services for youth with a history of running away from home.