The computed tomography (CT) of skeletal muscles was performed on 12 patients with myotonic muscular dystrophy (MyD). We have sliced at seven levels; those are 1. neck level-at the level of thyroid cartilage 2. shoulder girdle level-at the level of upper edge of sternum 3. upper arm level-at the level of middle of upper arm 4. abdominal level-at the level of L3 vertebra 5. pelvic girdle level-at the level of middle inguinal ligament 6. thigh level-at the level of middle of thigh 7. lower leg level-at the maximum size level of lower leg. The characteristic changes of MyD are; the sternocleidomastoid muscles are most severely affected, and the paravertebral and straight abdominal muscles also tend to be severely atrophied with lower CT density. Concerning thigh levels, the deeply located muscles and muscles for extension are predominantly affected. At the lower leg levels, the calf muscles are severely affected. The muscles of levator scapulae, trapezius, psoas major, iliopsoas, gluteus, and tibialis posterior tend to be preserved. In the tight, the compensatory hypertrophy is observed often in the rectus femoris muscles and rarely in the gracilis muscles with the involvements of the agonist muscles. It might be also important to examine the changes of muscles as a whole and to know the grade of atrophy for planning the life style. The CT examination would be recommended by this standpoint.