This report is the product of a 2-year project during which the Committee on Community-Level Programs for Youth, a 15-member panel, evaluated and integrated the current science on adolescent health and development with research and findings regarding program design, implementation, and evaluation of community programs for youth. It highlights essential elements of adolescent well-being and healthy development, offering recommendations for policy, practice, and research. It also discusses features of programs that can contribute to successful transition from adolescence to adulthood. Ten chapters include the following: (1) "Setting the Stage" (e.g., committee charge and U.S. youth); (2) "Adolescent Development"; (3) "Personal and Social Assets that Promote Well-Being" (e.g., how to measure wellbeing and theoretical perspectives); (4) "Features of Positive Developmental Settings"; (5) "The Landscape of Community Programs for Youth" (e.g., insights from nonexperimental schools and features of community programs); (6) "Lessons from Experimental Evaluations" (e.g., reviews and meta-analyses of evaluations and three model program evaluations); (7) "Generating New Information" (evaluating community youth programs and questions asked in comprehensive evaluations); (8) "Data and Technical Assistance Resources" (e.g., uses of social indicator data and data sources); (9) "Funding and Support for Programs"; and (10) "Conclusions and Recommendations." Four appendixes include fundamental principles of human development, theoretical frameworks for conceptualizing positive developmental processes, biographical sketches, and related reports from the National Archives. (Contains approximately 780 references.) (SM)