Substance use disorders account for approximately 6% of deaths worldwide and cost about $700 billion in the United States. Approximately 80% of drug users begin using during adolescence, underscoring the public health importance of effective substance prevention programs for youth and families. Prevention science designates 3 intervention categories: (1) universal prevention, targeting all individuals in the population, (2) selective interventions, targeting high-risk groups, and (3) indicated prevention interventions for youth with risk-taking behaviors. School-based and non–school-based interventions are reviewed, as well as the limitations of existing research, gaps in access and availability, and directions for future research and development.