A 70-year-old male began to show akinesia, rigidity of extremities, finger tremor, disturbed vertical external ocular movement, and nuchal dystonia, which progressed slowly. Brain CT scan and magnetic resonance images showed slight atrophy of the frontal lobe and slight enlargement of the lateral ventricles. Hasegawa's dementia rating scale-revised version gave a moderate score of 11/30 points. He died of pneumonia at the age of 76. The clinical diagnosis was progressive supranuclear palsy (PSP). However, there were no neuropathological characteristics of PSP. Neuropathologically, Parkinson's disease was diagnosed. In addition, many argyrophilic grains (ArGs) in the gray matter were stained, especially in the insula, amygdala, hippocampus, parahippocampal gyrus, lateral occipitotemporal gyrus, and substantia nigra, by the Gallyas-Braak method. We consider that ArGs could modify the symptoms of Parkinson's disease and that Parkinson's disease with ArGs may show a PSP-like clinical course.