Each year in the United States, an estimated 30 million children and adolescents participate in organized sports, and approximately 150 million adults participate in some type of nonwork-related physical activity. Engaging in these activities has numerous health benefits but involves a risk for injury. CDC analyzed data from the National Electronic Injury Surveillance System All Injury Program (NEISS-AIP) to characterize sports- and recreation-related injuries among the U.S. population. This report summarizes the results of that analysis, which indicate that during July 2000-June 2001 an estimated 4.3 million nonfatal sports- and recreation-related injuries were treated in U.S. hospital emergency departments (EDs). Injury rates varied by sex and age and were highest for boys aged 10-14 years. Effective prevention strategies, including those tailored to specific activities and those aimed at children, adolescents, and adults, are needed to reduce sports- and recreation-related injuries in the United States.