A systematic search for cases of adult-onset hereditary ataxia was conducted on location in Scotland. The investigation resulted in the discovery of eight pedigrees with 42 patients of whom 16 were alive in 1975. Nine patients were examined by the authors and recent hospital records were available on the remaining seven. The clinical features were quite variable. In declining order of frequency, findings were gait and limb ataxia, dysarthria, hyperreflexia, extrapyramidal motor disturbances, impaired vibratory sense, spasticity, defects of extraocular movements and nystagmus, reflex depression, Babinski signs, impaired joint position sense, muscle weakness, optic atrophy, and mental abnormalities. Foot deformity occurred only once. Inheritance was compatible with autosomal dominant transmission, but complicated by consanguinity in two families. The minimum prevalence was calculated as 0.31/100,000. Autopsy in two members in one family revealed olivopontocerebellar degeneration.