Several trends have come together to intensify interest in how public libraries might best support the interests and needs of youth in their communities. This study reports on findings from the Public Libraries as Partners in Youth Development (PLPYD) Initiative, a four-year, nine-site initiative funded by the Wallace Foundation to develop innovative models for public libraries to provide high-quality educational enrichment and career development programs serving underserved low-income children and youth. The nine libraries participating in the Initiative included both leading urban libraries and smaller county systems. This evaluation evaluated four questions: (1) Were particular youth programs and implementation strategies more or less effective in furthering the broad goals of the Initiative? (2) What are the costs of developmentally-enriching youth employment programs for public libraries, and how might such programs be financed? (3) What were the most important benefits and difficult challenges of the Initiative for participating youth, library staff, and the overall library system? (4) What lessons does the Initiative offer the broader field regarding the capacity of public libraries to provide services, programs, and jobs that meet the developmental needs of youth? The evaluation reveals that public libraries can be a resource for youth in low-income communities. In addition to providing access to technology and a "safe" place to be during out-of-school hours, evaluation results indicate libraries can provide high-quality youth employment programs that include training in both specific job skills and more general personal and social skills. These programs also can have positive impacts on the library system and the community. However, to work intensively with youth requires time, financial resources, dedicated staff, consistent leadership, and alignment of youth program with library's core mission and goals. Thus, public libraries need to assess and build their capacity for youth programs and services in a systematic way. Section I, Chapter 1 provides background information on public libraries, youth development, and the structure and evaluation of the Initiative in order to establish a broader context for this discussion. Chapter 2 provides a detailed overview of the nine PLPYD projects, as well as the community and institutional contexts that shaped their implementation. In Section II, Chapters 3 through 5 focus on the implementation of the Initiative. Chapter 3 examines general patters of youth participation in these programs, and Chapter 4 discusses staffing, institutional support, and community partnerships. Chapter 5 analyzes the cost and financing of programs that employ teens as homework help or general library assistants, both of which were central to the Initiative. Chapters 6 and 7 in Section III consider the impact of the Initiative for participating youth (Chapter 6) and participating libraries and their communities (Chapter 7). In Section IV, the concluding chapter discusses the lessons learned from the PLPYD Initiative and reflects on the role of public libraries in supporting youth, particularly in low-income communities. The appendices present an overview of the nine PLPYD initiative sites, the PLPYD evaluation methodology, and the PLPYD cost and financing study. (Contains 18 tables, 7 boxes, and 2 figures.)