Preventing Youth Problems provides information needed to prevent five of the most common, costly, and dangerous problems of adolescence: anti-social behavior, tobacco use, alcohol and drug abuse, and sexual behavior that risks disease and unwanted pregnancy. Over the past thirty years, scientific research on children and adolescents identified the major conditions influencing each of these problems. Each of the chapters in this volume provides a concise summary of what is known about one of these five problem behaviors. Each chapter covers the following essential points: – Incidence, prevalence, and cost of the problem, vital for gauging the importance of preventing the problem and for making the case for such efforts in public discussion of priorities; – Biological and environmental influences which increase or decrease the likelihood of these problems; and, – Principles, programs and policies that have been shown to reduce the incidence of each problem, information that can help in prevention of these behaviors.