Background. Friedreich’s ataxia is an autosomal recessive, neurodegenerative disease with a prevalence of 1 - 2 : 100 000. Ninety five % of cases are caused by Friedreich’s ataxia expansion of GAA triplet repeat in the first intron of the X25 gene. The gene is mapped on chromosome 9q. The objective of the investigation was to introduce simple and reliable DNA diagnosis helping to specify of spinocerebellare ataxias. Methods and Results. Our diagnosis is based on the differentiation of normal and mutant alleles of gene X25 with PCR and electrophoresis on agarose gel. Size of PCR product of normal allele is in our case 521 - 614 bp. It is responding to 7 - 38 GAA triplets. Size of mutant alleles with 200 - 1200 GAA triplets is as 4100 bp. After the method was introduced, we analysed 12 probands. Four of them suffered from Friedreich’s ataxia. Conclusions. We introduced a fast, non-radioactive, reliable DNA diagnostic method. The contribution of this method is defection of carriers and we can screen of families with the risk of Friedreich’s ataxia.

        Key words: Friedreich’s ataxia, X25 gene, frataxine, GAA expansion, direct DNA diagnosis, PCR.