The study showed that a positive youth development (PYD) intervention that included an evidence-based substance use prevention component adapted for an urban after-school setting was effective in preventing adolescent substance use. Adolescents participating in the intervention were significantly more likely to view drugs as harmful at program exit, and demonstrated a significantly reduced incidence of past-30-day use of alcohol, marijuana, or other drugs, as well as any drug use 1 year after program enrollment. The overall results of this study support the findings of a recent extensive review of PYD programs that showed that such approaches could be effective in the prevention of problem behavior among adolescents. PYD is an emerging area of practice and research that emphasizes a strengths-based approach to the promotion of positive outcomes for youth. This study examined one such program, the Positive Youth Development Collaborative (PYDC) which targets substance use attitudes and behaviors among urban minority adolescents. The program involves the implementation of an evidence-based curriculum embedded in a comprehensive after-school program based on PYD principles that is intended to prevent substance use. A total of 304 adolescents participated in the study. Figures, tables, references