A systematic review was conducted to examine the barriers to, and facilitators of, physical activity among young people (11-16 years). The review focused on the wider determinants of health, examining community- and society-level interventions. Four trials and 16 studies of young people's views were included. Evidence for the effectiveness of the interventions was limited, with some suggestions of improvements in knowledge and possible differences according to gender. Young women in particular identified barriers to physical activity associated with certain ways of providing physical education in schools. Young people in general identified a need for increased choice and facilities within the community and emphasized physical activity's social side. Some of the barriers and facilitators identified by young people had been addressed by "soundly evaluated" effective interventions but significant gaps were identified where no evaluated interventions appear to have been published (e.g. initiatives explicitly addressing gender issues or the combination of sport and other leisure activities), or where there were no soundly evaluated interventions. Rigorous evaluation is required particularly to assess initiatives that address the limited practical and material resources that young people identify as barriers to physical activity. (Contains 3 tables and 1 figure.)