A gene locus for autosomal dominant cerebellar ataxia (ADCA) has been found on chromosome 6p and named spinocerebellar ataxia 1. However, linkage exclusion from chromosome 6p and thus locus heterogeneity has been proven in Cuban ADCA, the largest known collective of ADCA patients, probably due to a founder effect. Two chromosomal regions were analyzed for linkage to Cuban ADCA: chromosome 4, since a pericentromeric inversion has been reported in a member of a European ADCA family, and chromosome 11q22-23, since it is known to contain the gene locus for ataxia telangiectasia, the main autosomal recessive disorder of cerebellar degeneration. In neither region was evidence for linkage found.