A spinocerebellar degeneration is described affecting ten members of a family over five generations with transmission by X-linked recessive inheritance. The clinical features include pes cavus, scoliosis, increased lumbar lordosis and signs of cerebellar dysfunction. There is a slowly progressive distal muscle atrophy, pyramidal weakness, brisk tendon jerks and the plantar responses are extensor. Sensory abnormalities were observed only in the two eldest members and consisted of mild impairment of position and vibration sense. A sural nerve biopsy showed loss of large diameter fibres and uniformly short internodal lengths as is usually found in Friedreich's ataxia. However, the electrophyisological findings of retained sensory action potentials and reduced motor conduction velocities contrast with those of Friedreich's ataxia. Post-mortem examination of one of the affected members revealed spinal cord pathology similar to that seen in Friedreich's ataxia with degeneration of the dorsal columns, and spinocerebellar and corticospinal tracts although the loss of Purkinje cells in the cerebellum was greater than is usually seen in that condition.