The purpose of the investigation was to determine the effect of the tonic neck posture upon fatigue induced by exhaustive exercise of the knee extensor muscles of college women. The subjects were college females enrolled in physical education activity classes at North Texas State University. The F ratio was used to determine significance of the difference in fatigue measures in the three head positions. The results of the present investigation revealed no statistically significant difference between the three head positions with respect to their influence on endurance of the leg extensors. Conclusions were that the tonic neck reflex does not facilitate or inhibit leg extensor endurance.