Spinocerebellar ataxia type 5 (SCA5), one of the genetically heterogeneous autosomal dominant cerebellar ataxias, was assigned to chromosome 11 in a single family descending from the grandparents of President Abraham Lincoln. We report a second, apparently unrelated, SCA5 family of French origin. The overall clinical picture was a slowly progressive cerebellar syndrome beginning mostly in the third decade (27+/-10 years, range 14 to 40). MRI showed a marked global cerebellar atrophy similar to SCA6.