Oxidative stress including DNA oxidation is implicated in Parkinson’s disease (PD). We postulated that DNA repair enzymes such as 8-oxoguanosine DNA glycosylase (OGG1) are involved in the PD process. We performed immunohistochemical and biochemical studies on brains of patients with PD and those of patients with progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD) as disease controls, and control subjects. We found higher expression levels of mitochondrial isoforms of OGG1 enzymes in the substantia nigra (SN) in cases of PD. Furthermore, Western blot analysis revealed high OGG1 levels in the SN of the patients with PD. Our results indicate the importance of oxidative stress within the susceptible lesions in the pathogenesis of PD.