Background: Few studies have compared injury rates on natural grass and FieldTurf surfaces, especially in interscholastic populations. No prior studies have reported if injury rates are different during practice and games in football and soccer on these two surfaces. Hypothesis: We theorized that there would be no difference in injury rates for football and soccer players when playing on natural grass or FieldTurf surfaces. Objective: To compare the incidence of injury of high school football players on natural grass and FieldTurf surfaces. Study Design: Retrospective study. Setting: Natural grass and FieldTurf surfaces at a high school in Western Washington. Sample Population: A total of 539 boy and girl athletes who participated in eight football and sixteen soccer teams during 1998 to 2001 interscholastic seasons. All injuries were reported and verified by an athletic trainer/physical therapist. Injury rates were determined per 1,000 athletic exposures. Main Outcome Measure: Reportable injuries occuring from participation as a varsity or junior varsity football or soccer athlete. Results: Injury rates on natural grass were significantly higher on FieldTurf for football and girls’ soccer. Injury rates on natural grass were significantly higher on natural grass than FieldTurf for practices and games for boys’ football and girls’ soccer. No significant differences were found between natural grass and FieldTurf in head related trauma for football players. For other body locations, higher rates of knee injury for football and ankle injuries for girls’ soccer occurred on natural grass compared to FieldTurf. By injury type, higher rates of spains for girls’ soccer and strains for football occurred on natural grass compared to FieldTurf. By position, for football, we found higher rates of injury on natural grass than FieldTurf for lineman and defensive backs. For girls’ soccer defenders had higher rates on natural grass than FieldTurf. Conclusion: The results of this study suggest that a new generation of synthetic turf, FieldTurf, may lower the risk of injury in football and girls’ soccer at the high school level. Further studies are needed to compare the risk of injury between the two surfaces in other high school sports like field hockey or lacrosse that also play on these surfaces.