ObjectiveTo determine the incidence rate of injury among high school cross country runners over a 15-year period.DesignProspective–longitudinal.SettingTwenty-three high schools in western Washington State under the surveillance of the University of Washington Athletic Health Care System between 1979–1994.ParticipantsOne hundred and ninety-nine cross country teams.Main Outcome MeasureInjuries resulting from running in a cross country practice or meet.ResultsThere were 1,622 injuries for an overall injury rate of 13.1/1,000 athletic exposures (AEs), i.e., participation of a runner in a practice or meet. Girls had a significantly higher overall injury rate (16.7/1,000 AEs) than boys (10.9/1,000 AEs) (p < 0.0001). Girls also had significantly higher injury rates than boys for both initial (p < 0.0001) and subsequent injuries (p < 0.0001), especially those at the same body location (p = 0.0001). This difference in risk estimates was consistent over a 15-year period. Nearly three-fourths of the injuries resulted in ≤4 days of disability. Overall, higher rates of initial injuries were reported during practices (9.2/1,000 AEs) than in meets (7.8/1,000 AEs) (p = 0.04). Shin injuries had the highest overall rates of new injury (1.9/1,000 AEs) and reinjury at the same body location (53.9/1,000 AEs). Girls had significantly higher initial injury rates than boys for shin (p < 0.0001), hip, and foot injuries (p < 0.01), and higher reinjury rates for knee, calf, and foot injuries, respectively (p < 0.05).ConclusionThe results of this study suggest that girl cross country runners are at higher risk of injury and reinjury than boy cross country runners.