High levels of inactivity in youth have led researchers and practitioners to focus on identifying the factors that influence physical activity behaviors in young people. The present study employed a qualitative ecological framework to examine the intrapersonal, social, and environmental factors influencing youth physical activity. In grade-specific focus group settings, 160 youth in grades 7 through 12 (aged 12 to 18) were asked how they would increase the physical activity levels of youth their age. Participants identified eight factors that they felt should be addressed in programs and interventions designed to increase the physical activity behaviors of youth. These factors included the importance of fun, having the time to be physically active, the benefits of activity, being active with friends, the role of adults, and the importance of being able to access facilities in their neighborhood. (Contains 1 table.)