Background Despite the progress in the knowledge of Huntington disease (HD) in recent years, the epidemiology continues uncertain, so the study of incidence becomes relevant. Methods Descriptive retrospective study with 188 individuals. Incidence of HD was calculated from the ratio of number of symptomatic cases newly diagnosed per million inhabitants per year during the period 2007–2019 in Aragon (Spain). Results 50 (27.9%) incident cases of HD (CAG repeat length ≥ 36) were identified from a

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... tal of 179 persons studied. The remaining 129/179 (73.4%) were HD negative (CAG repeat length < 36). Male to female ratio was 1:1,4; with 29 (58.0%) females and 21 (42.0%) males confirmed HD cases. The overall incidence was 6.48 per million patient-years. 12/50 positive HD cases (24,0%) were identified by performing a predictive test, without clinical symptoms. The minimum number of CAG repeats found was 10 and the most common CAG length among HD negative individuals was 16. Conclusions Our incidence lied within the range reported for other Caucasian populations. Implementation of new techniques has allowed to determine the exact number of CAG repeats, which is especially important in patients with triplet expansions in an HD intermediate and/or incomplete penetrance allele, both in diagnostic, predictive and prenatal tests.