The number of adolescents in the U.S. who engage in risk behaviors such as alcohol and drug use and unsafe sexual practices has reached alarming levels, with Hispanic adolescents in particular reporting high rates of substance use and sexual activity. This study explored risk and protective factors that influence high-risk behaviors in Hispanic adolescents. A theoretical model was developed based on an integration of Ecodevelopmental Theory and the Theory of Reasoned Action to investigate individual and social factors that affect the risk behaviors of Hispanic adolescents. This study was a cross-sectional, descriptive, secondary investigation of the baseline data of a combined sample of 493 Hispanic adolescent 7th and 8th graders and their immigrant parents who had been recruited for participation in the Familias Efficacy I and II studies. The hypothesized model of relationships included 3 direct effects variables: parent-adolescent communication about sex; adolescent condom use self-efficacy; and family functioning, which integrated 4 constructs: parental involvement; positive parenting; family communication; and parent-adolescent communication. The study model also included 3 indirect variables: parents' acculturation; differential acculturation; and parent's HIV knowledge. Three adolescent risk behaviors served as outcome variables: condom use; drinking alcohol while having sex ; and substance use. It was hypothesized that (1) family functioning, parent-adolescent communication about sex, and adolescent self efficacy would all be directly related to adolescent risk behaviors; (2) parent's acculturation would be related to adolescent risk behaviors indirectly through its association with parent's HIV knowledge and parent-adolescent communication about sex; and (3) differential acculturation would be related to adolescent risk behaviors indirectly through its association with family functioning, adolescent condom use self-efficacy, and parent-adolescent communication about sex. Cronbach's alpha computed for all measures yielded good to excellent reliability coefficients. Pearson linear correlation coefficients were calculated between all of the study variables, followed by confirmatory factor analysis to ascertain the feasibility of collapsing multiple indicators of family functioning and HIV/STIs risk behaviors into single latent variables. Finally, the hypothesized structural equation model was estimated. Beta coefficients were calculated to examine direct effects and Mackinnon's asymmetric distribution of product test was used to evaluate mediated effects. Data analysis failed to confirm any of the study hypotheses; however, post-hoc analyses yielded findings that merit further study. Family functioning emerged as the heart of the model, embedded within a web of direct and mediated relationships. Additional findings suggest that family functioning mediates the effect of parents' acculturation and of parents' HIV knowledge on adolescent risk behaviors. Study limitations include its cross-sectional design, self-report measures, convenience sample and integration of clinical and non-clinical samples. Suggestions are provided for researchers to further explore relationships among the variables, and recommendations made for community nursing practitioners to develop, implement and evaluate HIV/STIs prevention programs for Hispanic adolescents.