The purpose of this study was to determine the influence of position on knee flexor peak torque production. Gravity effect torque and knee flexor peak torque were measured in both supine and prone positions for 20 male and female volunteers between the ages of 22 and 35 years with no history of left lower extremity pathology. Knee flexor peak torques were corrected for gravitational error. No significant difference between the supine and prone gravity effect torque values was noted. This finding supports the validity of the gravity correction method used. The uncorrected supine knee flexor peak torque was significantly higher than the prone, a result which demonstrates the influence of gravity upon torque production. The corrected supine knee flexor peak torque was significantly lower than the prone. This result suggests that maximum knee flexor peak torque is generated prone rather than supine. Therefore, position should be considered in studies which compare knee extensor and flexor torque.J Orthop Sports Phys Ther 1988;9(8):279-283.