This research is about Mathare Youth Sports Association (MYSA), a unique urban self-help youth program in one of Nairobi's largest slums. This is a qualitative assessment of youth participation in the Environmental Clean-Up Program based on a premise that children and youth are an important group who need to be involved in planning and developing their communities. I examine how youth participate and the impacts of their participation on their personal lives, their families, communities, the local environment and institutions. I rely on Hart's (1992) definition which regards participation as sharing decisions that affect one's life and the life of community in which one lives. Given the shortage of comparative evaluations in youth participation, a combination of interviews and observations provide the depth and richness needed to better understand what youth are gaining from this program. I categorize the impact evaluation data into personal, familial, communal, institutional and environmental realms as identified by a PLAN International study in Ecuador, India and Kenya. My findings suggest that participation in MYSA motivates youth to clean and improve their neighborhoods. They clear heaps of garbage, unclog drains, plant trees and cut grass and weeds. They also pick rocks and broken bottles from grounds where children and youth from the local community play. Both parents and MYSA members gain personal knowledge about environmental cleaning, toxic waste and recycling By joining MYSA, young people also enhance their social networks, learn new skills and gain confidence about the future. This dissertation contributes to the understanding of how youth participate in programs designed to increase their community involvement. MYSA provides unique experiences and lessons that may help in the recognition of the capacity and abilities of young people to meaningfully participate in improving their lives in Kenya and world wide.