The purpose of this study was to determine the isokinetic strength of the quadriceps femoris and hamstring muscles in high school-aged students. Forty-seven 15- to 18-year-old high school volunteers served as subjects. Data were gathered on each subject by a questionnaire, lower extremity musculoskeletal assessment, and isokinetic testing of the two muscle groups at 60°/sec and 180°/sec. This study found no age effect on peak torque and no significant differences in peak torque between dominant and nondominant limbs. Significant differences (p < .001) occurred between the isokinetic strength of male and female subjects. The average hamstring muscle to quadriceps femoris muscle torque ratio was 57 percent at 60°/sec and 70 percent at 180°/sec. A value of foot pounds of torque per kilogram of body weight was provided as a guideline for clinicians. This investigation supports several findings already reported for other age groups.