The basiparallel cut is a nearly horizontal slice of the posterior fossa used in air study and the structures are observed on a plane parallel to the clivus. Total shrinkage of the cerebellum, with or without fourth ventricle dilatation, was found in cases of olivopontocerebellar atrophy, some intoxications, and a few senile subjects. Some atrophy of paleocerebellar portions was seen in Holmes-type degeneration. Another pattern was symmetric shrinkage of neocerebellar lobules and relatively specific for the cases of 'multiple system atrophy' such as progressive supranuclear palsy, striatonigral degeneration, Marie's ataxia, etc. Loss of the superior cerebellar peduncle was clearly demonstrated in this view.