In two families with autosomal dominant olivopontocerebellar atrophy (type IV), 15 affected and 44 unaffected members were typed for 28 genetic markers, including HLA. The lod scores for a possible HLA linkage, plotted against recombination fractions from 0.01 to 0.4, were negative. No evidence emerged for the presence of the ataxia-locus within measurable distance of the HLA-loci on chromosome 6. No indications were obtained that the ataxia-gene is linked with one of the other marker-genes.