Most unprotected sex occurs in close relationships. However, few studies examine relational factors and sexual risk among high-risk populations. Romantic Attachment Theory states that individuals have cognitive working models for relationships that influence expectations, affect, and behavior. We investigated the influence of attachment avoidance and anxiety on sexual beliefs (e.g., condom use beliefs, self-efficacy), behavior (e.g., condom use, multiple partners, unprotected sex with risky partners), and sexually transmitted infections (STIs) among 755 high-risk, young pregnant women (ages 14-25) recruited from urban prenatal clinics. Attachment anxiety predicted sexual beliefs, condom use, and unprotected sex with risky partners controlling for demographic variables. Sexual beliefs did not mediate the relationship between attachment orientation and sexual behavior. Current relationship with the father of the baby did mediate the effect of attachment anxiety on multiple partners and STIs. Results indicate the importance of including general relational factors, such as attachment, in HIV prevention.