The normal values of glycogen contents in skeletal muscles in commonly used experimental animals and men were studied. In addtion, this study was designed to know the relationship between amount of exercise and glycogen content in muscle, and to know the causes of species difference. Glycogen contents were determined in quadriceps, gastrocnemius, and triceps in mouse, rat, rabbit, and man. The results of this study as follows: The value of glycogen content in human skeletal muscle is significantly higher than that of experimental animals. The heavier the body weight of experimental animal, the higher the value of glycogen content in each muscle. The value of glycogen content in gastrocnemius is higher than that of quadriceps. The value of glycogen content in quadriceps is higher than that of triceps.