The present studies are designed to determine whether the NMES can affect the muscle atrophy in rats following administration of steroid. Rats were divided into four groups: 1) Control group treated with administration of distilled water. 2) The group treated with administration of steroid. 3) The group treated with NMES once a day after adminstration of steroid. 4) The group treated with NMES twice a day after administration of steroid. The muscle atrophy was induced by one week administration of dexamethasone once a day by 3 mg/kg. The change in the structure of muscle fiber and the amount. of myofibril protein and gastrocnemius were determined after every week dissection of the tissues. The results were as follows; 1. The administration of steroid significantly affected the decrease in the weight, but NMES did not affect the inhibition of decrease in the weight. 2. The weight of gastrocnemius in the group once treated with NMES was changed two weeks later; similarly in the group twice treated with NMES significantly did two or three weeks later. These indicated that NMES affected the muscular activation of gastrocnemius(p<.05). 3. The changes in the amount of gastrocnemius protein by NMES might, indicate that NMES activated the capacity of synthesis of muscle fiber protein(p<.05).