Hereditary ataxias are a heterogeneous group of progressive neurodegenerative disorders characterized by symptoms and signs originating mainly in the CNS. A new representative of this disease group is infantile onset spinocerebellar ataxia, an autosomal recessively inherited syndrome so far reported only in the genetically isolated Finnish population. The etiology of hereditary ataxias still remains unknown, but the gene loci behind many of them have been mapped to different chromosomal regions. We have carried out linkage analyses with markers on the regions of the previously identified ataxia loci to determine whether the infantile onset spinocerebellar ataxia syndrome represents the same allelic disease as any of the previously identified hereditary ataxias. Here we report that the infantile onset spinocerebellar ataxias syndrome does not segregate with any of the markers closely linked to the other hereditary ataxias. Consequently, it represents a genetically distinct disease, the gene locus of which still has to be identified.