The purpose of this study was to determine the effect of regular exercise during dexamethasone injection on the body weight, weight of hindlimb muscles and adrenal gland in young rats. 80-100g Wistar rats were divided into control, exercise, dexamethasone injection(dexa), and exercise during dexamethasone injection(D+E) group. The dexa group received daily subcutaneous injection of dexamethasone at a dose of 5mg/kg body weight for 10 days. The exercise group ran on a treadmill for 60min/ day(20 minutes every 4 hour at 10m/ min and a 10degrees grade. The control group received daily subcutaneous injection of normal saline at a dose of 5mg/kg body weight for 10 days. The D+E group ran on a treadmill for 60min/day(20 minutes every 4hour) at 10m/min and a 10degrees grade. Body weight of both control and exercise group increased significantly until 10 days, the of both dexa and D+E group decreased significantly, resulting in 79.47 and 78.75% decrease respectively compared to the first day of experiment. Body weight and muscle weight of the soleus, plantaris and gastrocnemius decreased significantly with dexamethasone injection. Relative weight of the dexa group decreased significantly compared to that of the control group. Body weight and muscle weight of the soleus and plantaris of the D+E group showed a tendency to increase, and muscle weight of the gastrocnemius increased significantly compared to the dexa group. The Relative weight of the plantaris was comparable to the control group and that of the soleus and gastrocnemius tended to increase, in the exercise group. Body weight and muscle weight of the soleus and plantaris of the D+E group showed a tendency to increase, and muscle weight of the gastrocnemius increased significantly compared to the dexa group, The Relative weight of the soleus and gastrocnemius tended to increased and that of the plantaris of the D+E group increased significantly compared to the dexa group. Body weight, muscle weight and relative weight of the soleus, plantaris and gastrocnemius of the D+E group increased significantly compared to the dexa group Adrenal gland weight of the dexa and D+E group tended to increase, and that of the exercise group increased significantly. From these results. it can be suggested that regular exercise during dexamethasone injection might attenuate the decrease of body weight and hindllimb muscle weight induced by the dexamethasone injection.