A number of previous studies have found that peers influence adolescent sexual behavior. Still, it remains unclear how the mechanisms of peer influence operate on the sexual behavior of adolescents. This is unfortunate because it limits theoretical clarity and inhibits the production of policy aimed at reducing adolescent sexual behavior. Using data from the National Longitudinal Study of Adolescent Health, this thesis extends upon current literature and determines the role of peer attitudes and behaviors on different forms of adolescent sexual behavior as measured by peer self-report data while addressing other limitations of previous research such as whether or not mechanisms of peer influence are conditioned by adolescent involvement with peers. The discussion of this work centers around the theoretical implications of the findings that peers do not influence all forms of sexual behavior and peer behaviors seem to be the only mechanism of peer influence that predict sexual onset.