Ten cases of PSP were examined for the presence of neocortical and hippocampal lesions. Samples from 10 cortical areas were stained by Bodian's method and by tau, ubiquitin and beta A4 immunocytochemistry. For the sake of comparison, 5 Alzheimer's cases were studied with the same techniques. Neocortical tangles, star-like tufts of fibers, and neuropil threads were seen in all the cases of PSP. They were stained by Bodian's technique and labelled by an anti-tau, but not by a polyclonal anti-ubiquitin antibody. Senile plaques (Bodian's technique), diffuse or focal amyloid deposits (beta-A4 immunohistochemistry) were rare or absent. The density of tangles was the highest in area 4 and the lowest in area 17. In area 4, the tangles were mainly located in layers V-VI. By contrast, the Alzheimer's tangles had a bimodal distribution (layers III and V-VI). These results favor the specificity of cortical alterations in PSP.