This study examined the roles of the initial level of muscle glycogen content and available substrate on glycogen repletion in muscle. The rats were randomly assigned to normal, starvation and exercise groups. The glycogen content of muscle was lowered by starvation and exercise for the purpose of this experiment. The normal rats remained sedentary in their cage without any restriction of food and water. The exercise and starvation groups were divided each group into two subgroups depending on the degree of stress, i.e. 16 and 64 hours starvation, and 30 minutes and 2 hours exercise loading. All experimental aninals sacrificed 9~10 O'clock in the morning. The glycogen content of gastrocnemius and liver were 0.416+0.0433 and 1.70+0.410gm/100gm wet tissue in normal rats, respectively. The glycogen content of gastrocnemius in stravaton groups was reduced to 83.5 and 75.5% of the values of normal groups by starvation for 16 and 64 hours, respectively. In exercise group, the content of glycogen was reduced to 63.7 and 49.8% of the normal group by 30 minutes and 2 hours exercise loading, respectively, After above exercise loading and forced starvation, glucose, 2.0gm/100gm body weight was ingested, and 2 hours later the glycogen content was determined to evaluate the role of initial level of muscle glycogen content on the repletion in gastrocnemius, and the different amount of glucose, 1.0, 1.5 and 2.0mg/100gm body weight, was given orally, and 2 hours later the glycogen content of gastrocnemius was determined to evaluate the role of available substrate on the glycogen repleted in muscle of the lowest initial glycogen content, and the larger the amount of glucose ingestion, the larger amount of glycogen repletion in muscle. The experiment demonstrates that the reducing level of muscle glycogen and increased amount of available substrate are the important factors for the acceleration of muscle glycogen repletion, and in the aspect of repletion of glycogen, the repletion rate of liver glycogen is 2~5 times faster than that of muscle, whereas there is no difference of repletion rate of liver glycogen between starvation and exercise groups.