Two siblings and a third child exhibited a syndrome of progressive muscular weakness and wasting, closely resembling Werdnig-Hoffmann's disease. Autopsy of one of the siblings and the third child showed nearly total absence of myelin sheaths in the cranial and spinal nerve roots, relative preservation of axons, and normal neurons in the motor cranial nerve nuclei and anterior spinal gray matter. The mother of the siblings had bilateral pes cavus, and the father of the third child had a sensory-motor polyneuropathy dating to childhood, associated with pes cavus and scoliosis. The disorder in these children and in a few similar cases in the literature shares some features of Charcot-Marie-Tooth disease and the hypertrophic neuropathy of Déjerine-Sottas, but it is difficult to classify as either of these familial neuropathies as presently defined. Elevation of cerebrospinal fluid protein is a useful finding in distinguishing such children from patients with Werdnig-Hoffmann's disease.