The role that environmental factors play in driving HIV and STI transmission risk among street-involved youth has not been well examined. We examined factors associated with number of sex partners using quasi-Poisson regression and consistent condom use using logistic regression among participants enroled in the At Risk Youth Study (ARYS). Among 529 participants, 253 (47.8%) reported multiple partners while only 127 (24.0%) reported consistent condom use in the past 6 months. Homelessness was inversely associated with consistent condom use (adjusted odds ratio [aOR]=0.47, p=0.008), while unstable housing was positively associated with greater numbers of sex partners (adjusted incidence rate ratio [aIRR]=1.44, p=0.010). These findings indicate the need for interventions which modify environmental factors that drive risk among young street-involved populations.