Histopathological changes seen in progressive supranuclear palsy (Steele-Richardson-Olszewski disease) have been thought to be located in subcortical nuclei. However, abundant neurofibrillary tangles have been found recently in several neocortical areas. Their morphology and ultrastructure, regional and laminar distributions, as well as antigenic and biochemical properties make them clearly different from the neurofibrillary tangles observed in Alzheimer's disease and aging. Tau positive fibrillary accumulation in the nevroglia has also been seen in the cortex. The topographical distribution of the lesions is rather stereotyped, but some uncommon distributions (such as pallido-luysonigral) have been identified. Factorial analysis has shown that cortical and subcortical lesions are independent; pedonculopontine nucleus could play a role in the cortical diffusion of the lesions.