This proposal seeks to expand the research base regarding influences on adolescent HIV/STD risk, a priority of Health People 2010. Specifically, the proposed research will add to our understanding of the role of parenting and peer relationships in sexual risk and the co-occurrence of sex and substance use. The aims of this proposal are to 1) to explore the effects of peer selection and socialization during adolescence on high risk sex, the co-occurrence of sex and substance use, and young adult outcomes such as HIV/STD diagnoses, 2) explore the direct effects of parenting and family relationships on adolescent attitudes and behaviors related to sex, and 3) explore the effects of the interaction between family and peer influences on high risk sex, attitudes about sex, and the co-occurrence of sex and substance use. Peer influence is conceptualized as a simultaneous process of selection and socialization through behavior and attitudes regarding the costs of sex. Family influences to be studied are parental involvement, communication, closeness, attitudes, and parental communication about high risk sex and prevention of sexually transmitted diseases. Data from the saturated schools sub-sample of the National Longitudinal Study of Adolescent Health (Add-Health) will be used to create a three-wave data set (2 adolescent waves, 1 young adult wave) to address these questions. Composite measures of sexual attitudes, substance use, and HIV/STD diagnoses will be created using item response theory and confirmatory factor analysis methods where appropriate. Generalized linear models with distributions and linkages appropriate for the dependent variables will be used to test hypotheses related to each of these aims. The results from this research will assist developers of family interventions and interventions addressing peer norms by adding to our understanding of peer influences and the interaction between parent and peer influences on sexual behavior. [unreadable] [unreadable] [unreadable]