© by the National Athletic Trainers' Association, Inc Context: In 2010, 8.6 million children were treated for unintentional injuries in American emergency departments. Child engagement in sports and recreation offers many health benefits but also exposure to injury risks. In this analysis, we consider possible developmental risk factors in a review of age, sex, and incidence of 39 sport and recreational injuries. Objective: To assess (1) how the incidence of 39 sport and recreational injuries changed through each year of child and adolescent development, ages 1 to 18 years, and (2) sex differences. Design: Descriptive epidemiology study. Setting: Emergency department visits across the United States, as reported in the 2001-2008 National Electronic Injury Surveillance System database. Patients or Other Participants: Data represent populationwide emergency department visits in the United States. Main Outcome Measure(s): Pediatric sport- and recrea-tion-related injuries requiring treatment in hospital emergency departments. Results: Almost 37 pediatric sport or recreational injuries are treated hourly in the United States. The incidence of sportand recreation-related injuries peaks at widely different ages. Team-sport injuries tend to peak in the middle teen years, playground injuries peak in the early elementary ages and then drop off slowly, and bicycling injuries peak in the preteen years but are a common cause of injury throughout childhood and adolescence. Bowling injuries peaked at the earliest age (4 years), and injuries linked to camping and personal watercraft peaked at the oldest age (18 years). The 5 most common causes of sport and recreational injuries across development, in order, were basketball, football, bicycling, playgrounds, and soccer. Sex disparities were common in the incidence of pediatric sport and recreational injuries. Conclusions: Both biological and sociocultural factors likely influence the developmental aspects of pediatric sport and recreational injury risk. Biologically, changes in perception, cognition, and motor control might influence injury risk. Socioculturally, decisions must be made about which sport and recreational activities to engage in and how much risk taking occurs while engaging in those activities. Understanding the developmental aspects of injury data trends allows preventionists to target education at specific groups.