OBJECTIVES: To describe the incidence and characteristics of injuries among US high school rugby players and to identify possible injury risk factors. DESIGN: Descriptive epidemiological study. SETTING: The 2005 and 2006 US high school rugby seasons. PARTICIPANTS: A convenience sample of 121 boys' and girls' US high school rugby clubs. Main Exposures Exposure to playing rugby. MAIN OUTCOME MEASURES: Incidence, characteristics, and risk factors of rugby injuries. RESULTS: Enrolled clubs reported 594 injuries during 113,641 total high school rugby athletic exposures (81,627 practice exposures and 32,014 match exposures). Rugby injury rates were 5.2 injuries per 1000 total athletic exposures, 1.3 injuries per 1000 practice exposures, and 15.2 injuries per 1000 match exposures. The mean age of the injured athletes was 16.5 years (SD, 1.2 years; range, 13-19 years) and 87.0% were male. The most commonly injured body sites were the head (21.7%), ankle (13.3%), and shoulder (12.8%). Fractures (16.0%), concussions (15.8%), and ligament sprains (incomplete tears) (15.7%) were the most common diagnoses. Practice and competition injuries were similar with respect to the proportion of concussions and head, shoulder, ankle, and knee injuries. More than half of all injuries resulted from being tackled (30.8%) and tackling (28.8%). CONCLUSIONS: As the popularity of youth rugby continues to grow in the United States, increasing numbers of physicians and certified athletic trainers will find themselves treating rugby-related injuries and answering questions from parents about the comparative safety of rugby. To our knowledge, this is the first large-scale study to describe injury rates and identify possible injury risk factors among US high school rugby players.