The present study was designed to test a model of contextual and intrapersonal predictors of adolescent risky sexual behaviors and of sexually transmitted infection diagnoses. Using Waves I and II from the National Longitudinal Study of Adolescent Health, the authors estimated a structural model in which intrapersonal factors such as adolescents' attitudes about sex, perceived parental norms, knowledge about sexual health, and birth-control self-efficacy partially mediated the effects of contextual factors such as parent-adolescent relationship quality, school connectedness, and exposure to AIDS and pregnancy education on a number of risky sexual behaviors and outcomes: early sex initiation, sex under the influence of substances, condom use at last intercourse, and having been diagnosed with a sexually transmitted infection. Different patterns of direct and mediated effects emerged for each sexual outcome. Results are discussed in terms of the complex interplay between environment and individual and in terms of how, when, and with whom to intervene in order to improve adolescent sexual health outcomes. (Contains 4 tables and 2 figures.)