We describe a woman with a 13-year history of postural instability, vertical gaze palsy and dopa-responsive parkinsonism - a clinical profile that corresponds to progressive supranuclear palsy (PSP) and Parkinson's disease (PD). The patient died at the age of 82 years. Neuropathological features included neuronal loss and gliosis in the substantia nigra, locus ceruleus, dorsal motor nucleus of the vagus, thoracic intermediolateral nucleus and nucleus basalis of Meynert, in addition to the typical pathology of PSP. Immunohistochemical studies demonstrated that PSP-tau pathology was localized in the central nervous system, but Lewy body-related α-synucleinopathy was extensive in the central and peripheral nervous systems. Although PSP and PD may represent independent processes, this case could provide insight into a common defect in either protein phosphorylation or the proteinase surveillance system that contributes to human aging.