This comprehensive volume reviews current knowledge about multiple problem behaviours in adolescence, focusing on ‘what works’ in prevention and treatment. Cutting-edge research is presented on the epidemiology, development, and social costs of four youth problems that frequently co-occur: serious antisocial behavior, drug and alcohol misuse, tobacco smoking, and risky sexual behavior. A framework for reducing these behaviors is outlined, drawing on both clinical and public health perspectives, and empirically supported prevention and treatment programs are identified. Also addressed are ways to promote the development, dissemination, and effective implementation of research-based intervention practices. Authored by an interdisciplinary panel of experts, this is a state-of-the-science sourcebook and text for anyone working with or studying adolescents at risk.