There is a current lack of molecular studies analyzing the behavior of trinucleotide repeat expansions causative of Late Onset Spinocerebellar Ataxias in the Brazilian population. Therefore, this manuscript analyses normal families, as well as one hundred normal individuals of the Espirito Santo State to determine the trinucleotide repeat behavior and the allelic frequencies found in this population. The analysis of normal families demonstrated that, instead of being always stably transmitted over generations, expansions can occur between two generations of unaffected individuals, possibly contributing for the appearance of the ataxic phenotype. Allelic frequency studies demonstrated that some alleles are prevalent in the population, namely, allele 32 for the ATXN1 locus (21.5%); allele 21 for the ATXN2 locus (50%); allele 21 and 23 for the ATXN3 locus (14% each); allele 12 for the ATXN6 locus (21%) and allele 10 for the ATXN7 locus (22.5%).