Inherited spinocerebellar ataxias (SCA) are progressively degenerative neurological diseases. The primary site of degeneration is the cerebellar cortex--in particular, the Purkinje cells. In the present report, the SCA locus, inherited as an autosomal dominant trait in a large kindred, is localized to a region approximately 15 centimorgans telomeric of HLA-A on the short arm of chromosome 6.