Contrary to our results in SCA2 presymptomatic individuals, higher SOD3 and glutathione peroxidase activities and decreased levels of reactive oxygen species were found in presymptomatic individuals with spinocerebellar ataxia type 3 (SCA3), suggesting a potential antioxidant adaptive response to an oxidative challenge taking place before disease onset. The gene discussed is SOD3; the disease is Spinocerebellar ataxia type 3.