Progressive supranuclear paly (PSP) was firstly reported by Steel in 1964. This condition was separated from Parkinsonism by both clinical symptoms and neuropathological findings. Recently, in an attempt to improve diagnostic accuracy to give appropriate informed concepts and to select correct cases for drug studies or other research purpose, diagnostic criteria for PSP have been developed. PSP begins in the presenile period and duration of illness is 5.9 years (1.2-10.3 years; Maher and Lees, 1986). Cardinal clinical symptoms of PSP are supranuclear gaze palsy, neck dystonia, parkinsonism, pseudobulbar palsy, gait imbalance with frequent falls and subcortical dementia. Supranuclear gaze palsy and bradykinesia are essential for diagnosis. MR-imaging of PSP shows dilatation of the third ventricle. Other laboratory examinations show no specific findings. Neuropathologically, marked dilation of the third ventricle and volume loss of periaqueductal area of the midbrain are noted in macroscopic view. Microscopical examination reveals neuronal loss and gliosis in the tegmentum, the tectum, periaqueductal gray, the dentate-rubro-pallido-luysial area, and the inferior olivary nucleus. Neuropathological hallmarks of PSP are neuronal loss, presence of the globose typed neurofibrillary degeneration, and glial tangles (so called tuft shaped astrocyte and coiled body). Atypical cases of PSP are reported. Such cases are reported as pure akinesia, PSP without ophthalmoplegia, dementia predominant PSP, pathologically diagnosed pallido-nigro-luysial atrophy (PNLA), pathologically diagnosed corticobasal degeneration which showed no laterality, and so on. Reported cases as pure akinesia was diagnosed as PSP or PNLA by neuropathological findings. Improvement of diagnostic accuracy in PSP is expected to ithrapeutic trials, to investigate the etiology, and to separate the other clinical entity from PSP.