The author used the manual muscle tests in 17 patients with progressive muscular dystrophy. The data related to the degree of motor impairment showed that it is symmetrical in its distribution, but the larger joints are more deeply involved. On the other hand, varying impairment of the agonist and antagonist muscles of the same synergic unity accounts for the vicious attitudes usually seen. The author found a greater impairment in flexors of the head and trunk, in adductors of scapula, adductors of hips, flexors and extensors of limbs and in the dorsiflexors of the feet. This last feature is not conceded by some authors, for whom the gastrocnemius is the muscle most involved in the disease. The author holds the view that in spite of the untoward prognosis of the disease, exercises to avoid vicious positions must be performed.