The Authors describe the result of air encephalography in 5 cases of Progressive Supranuclear Palsy (P.S.P.). In all cases signs of cortical cerebral atrophy were found (with a marked dilatation of the lateral ventricles in two patients). Equally constant were signs of atrophy in the brain stem and cerebellum with involvement of the vermis (in its superior part in four cases and diffused in one case). In three patients there was also subcortical cerebellar atrophy. Among the alterations observed the slight cerebral cortical atrophy does not seem to be due to the pathological process peculiar to P.S.P., but rather to other processes such as senility, vascular alterations etc. Atrophy involving the brainstem and the cerebellum was of interest being a constant finding easily correlated with symptoms and with the site of P.S.P. process. These findings, though without specificity, offer useful data and help to assess the evolution of the disease.