We describe two kindreds with an autosomal dominant inherited disorder characterized by a variable degree of muscle weakness of limbs, vocal cords, and intercostal muscles and by asymptomatic sensory loss, beginning in infancy or childhood in severely affected persons. Life expectancy in severely affected patients is shortened because of respiratory failure. Because nerve conduction velocities are normal and it is an inherited axonal neuropathy, we classify the disorder as a variety of hereditary motor and sensory neuropathy type II (HMSN II) (HMSN IIc). The present report provides further evidence for heterogeneity among the hereditary motor and sensory neuropathy type II disorders. In one large pedigree with the type IIc disorder, no linkage to DNA markers known to map near the HMSN IA locus on chromosome 17p or the HMSN IB locus on chromosome 1q was demonstrated.