The number of children and adolescents participating in organised athletic activities worldwide is increasing. However, physical fitness levels among youth are lower today than in previous decades. The combination of increased exposure and decreased preparedness for sports participation has led to an epidemic of both acute and chronic sports-related injuries in this population. Poor physical fitness, in addition to having negative health consequences, seems to be a risk factor for sports-related injury. Accurate injury surveillance data are required to better define the magnitude of the problem of injury in youth sports, as well as to identify specific risk factors for injury. From these data, targeted intervention strategies incorporating fitness training may be developed with the goal of preventing sports-related injury. Preliminary experience with several specific injury patterns--anterior cruciate ligament injuries and ankle sprains--has demonstrated the efficacy of such targeted prevention strategies.