Homeless men in the U.S. represent a large and growing population, and have elevated rates of HIV/AIDS and sexual risk behaviors, including unprotected sex with women. We conducted qualitative interviews (n = 30) with homeless men using shelters and meal lines in downtown Los Angeles (Skid Row) to better understand how such men view the risks of sexual encounters with female partners. Men living on Skid Row perceived multiple risks, including HIV and unwanted pregnancy as well as emotional trauma, loss of resources, exacerbation of drug addiction, and physical attack. Respondents described using visual and behavioral cues, social reputation, geographical location, feelings of trust, perceived relationship seriousness, and medically inaccurate "folk" beliefs to judge whether partners were risky and/or condom use was warranted. Medically inaccurate beliefs suggest the potential utility of evidence-based interventions to change such beliefs. We also consider implications for relationships on the street and housing interventions.