Responsible decision-making is a cornerstone of drug abuse prevention programs but most attention has been focused on responsibility for one's own behavior. The proposed project conceives of health as a public issue for which there is a shared responsibility. The overall goals are a) to understand the phenomena of peer monitoring and intervention and b) identify those factors that predispose young people to develop a sense of shared responsibility, appreciate the public dimensions of risk behaviors, and dissuade peers from engaging in behaviors that compromise health such as smoking or alcohol abuse. To do this we propose a comparative, longitudinal, developmental study in two contrasting national contexts (the United States and Hungary). We will collect cross-sectional data from approximately 6,000 5th -12th graders and their teachers during the first year of the study. In addition, we propose a (3-year) panel study of approximately 2,000 early, middle, and late adolescents, their parents, and teachers as the adolescents make transitions to new school settings. The proposed study is designed to: (1) test the effects of family practices and classroom climates on the development of young people's attitudes toward social responsibility and their conception of health risks; (2) test whether higher levels of social responsibility and awareness of the public dimensions of risk increase the likelihood of intervening with peers; (3) test whether hypothesized developmental patterns exist in young people's commitment to the individual's right to make health risk decisions and their willingness to intervene with friends; and (4) to test whether differences in social environments are enough to explain differences in the willingness to intervene in friends behavior in two different cultures. The study will be conducted in 40 schools across Pennsylvania and 30 in the Republic of Hungary. Student and teacher surveys will be conducted in schools, while parents will be asked to respond by mail. The study will consist of a complex design that includes cross-sectional, longitudinal and comparative cross-national analyses using a number of analytic techniques including Hierarchical Linear Modeling to assess the effects of school climates on individual behavior and Structural Equation Modeling to test longitudinal hypotheses. Planned Missing Data design will be used to reduce the effects of study attrition.