Sexual risk behavior in adolescence can lead to adverse health consequences, particularly for female youth. Most interventions focus on imparting knowledge about the consequences of such behaviors, even though little research has examined whether increasing such knowledge results in desired behavioral changes. Further, individual factors such as impulsivity and childhood adversity might moderate this relationship. We examined associations between HIV knowledge and sexual risk behavior and condom use efficacy in a sample of 122 at-risk females, aged 13-18. HIV knowledge was unrelated to sexual risk behavior, but positively related to condom use efficacy. Impulsivity and childhood adversity had direct effects, with no interaction effects. Increasing HIV knowledge may play an important role in promoting proximal predictors of safer sex practices.