The five core concepts of CCYD are adult support and guidance, gap activities, work as a developmental tool, youth involvement in decision-making, and support through transitions. Lesson 1 was that it is possible to implement and sustain a neighborhood-wide youth development initiative, based on a common substantive framework, in resource-poor neighborhoods. Lesson 2 was that a set of research-based core concepts is extremely useful in helping communities generate consensus around what to do, move quickly to action, and stay on track. Lesson 3 was that it takes local leadership with credibility, resources, and commitment to partner with residents, get results within a reasonable period of time, and sustain a youth development effort. Lesson 4 indicated that variation and flexibility are essential to integrating residents into the program. Lesson 5 was that local infrastructure and previous programming experience play a critical role. Lesson 6 was that older and higher-risk youth are more difficult to attract and required targeted outreach. Lesson 7 was that it is critical to distinguish between youth involvement and youth leadership strategies and to provide adults with the training they need. Lesson 8 was that large-scale initiatives need a structured approach to assessing program quality on an ongoing basis. Lesson 9 was that placed-based initiatives couldn’t draw a fence around a neighborhood. Lesson 10 was that researching community initiatives may require new strategies, including closer engagement and timely, ongoing communication between researchers and sites. 5 tables, 13 endnotes, appendix