Youth substance use and misuse are still highly common, despite substantial efforts made to reduce the problem. Early start with substance use is often associated with more severe short- and long-term negative consequences for youth psycho-social adjustment. Bringing together international experts in the areas of prevention, health, and developmental science, this volume presents the most up-to-date knowledge about etiology (e.g., risk and protective factors) of substance use behaviors and the most effective interventions that can be implemented in the school setting. It also presents current hot topics in the field, such as: The importance of implementation fidelity for the success of the program The need to find effective ways to disseminate evidence based interventions and to understand whether those interventions are, in fact, cost effective. Taken together, these articles shed a light on what has been done and what still needs to be done to combat substance use among youth and suggest new theoretical perspectives and new practical approaches to address the problem. This is the 141st volume of New Directions for Youth Development , the Jossey-Bass quarterly report series dedicated to bringing together everyone concerned with helping young people, including scholars, practitioners, and people from different disciplines and professions.