The goal of the current study was to identify potential individual and environmental protective factors for sex risk behavior among homeless youth. We explored gender differences in the prediction of unprotected sex and number of sex partners. Data were collected from 192 sexually active, homeless youth who were 14-21 years old. High rates of sex risk behavior were reported. Significant gender differences were found in STD rates with 19% of females and 2% of males reporting an STD diagnosis during the previous three months. Findings indicated that positive expectations for the future were associated with fewer sex partners for both genders, whereas decision making skills predicted a lower percentage of unprotected sex for males and fewer sex partners for females. For females, univariate analyses indicated that self-esteem and having a natural mentor may reduce the likelihood of unprotected sex, whereas multivariate analysis indicated that being employed or in school may play a protective role with respect to number of sex partners.