Five main lessons were learned from the experiences of the YouthPeace and SisterNet programs: (1) creating social change takes time; (2) the concept of activism must be made developmentally appropriate for youth to understand; (3) youth must be prepared for challenges in mobilizing community support; (4) adult sponsors must teach the difference between simply doing service projects versus affecting social change; and (5) adult allies play a critical role in community mobilization. The article beings with a description of the YouthPeace and SisterNet program model, which utilizes a youth-driven approach to developing youth leadership and activism and preventing community violence. The programs bring together adult sponsors and community organizations to create local youth chapters. Youths are recruited and trained to positively impact their communities by: (1) defining their community; (2) assessing the community’s assets and needs related to violence; (3) planning an action based on the assessment findings; and (4) reflecting on the activism experience and planning future actions. The participatory evaluation was developed as a 3-year process. In the first year, evaluators worked with program staff to identify key program benchmarks and create a program-monitoring database. Case studies with four chapters were also conducted during the first year (2002-2003), which included observations of chapter meetings and actions and interviews with adult sponsors and youth members. During the second year (2003-2004), program benchmarks were monitored and interviews were conducted with youth members and adult sponsors. A youth evaluation team was created to design and implement a program evaluation to complement the adult evaluators’ work. During the third year (2004-2005), program benchmarks were monitored, program documents were reviewed, and chapter meetings were observed. The evaluation findings will help program staff and youth work more efficiently toward becoming community violence prevention activists. Figure, references