Department of Neurology, Northwestern University Medical School, Chicago, Illinois.

A case of non-progressive congenital myopathy is described in which there was absence of muscles and scapulo-peroneal distribution of weakness. The muscle biopsy showed preferential atrophy of Type I fibers and subsarcolemal bodies. These bodies were composed of an acidic protein with sulphahydryl groups which showed acid stable adenosine triphosphatase activity. The possibility of a maturational arrest as a cause is presented.