There is considerable debate on the role of the cerebrospinal fluid (CSF) in the production of hydrocephalus. In the case reported the following elements indicate that the overproduction of CSF was responsible for the development of hydrocephalus: 1) hypertrophy of the choroid plexus, demonstrated by angiography, biopsy and autopsy; 2) absence of obstacle to the CSF flow; 3) enlargement of the subarachnoid space, more evident at the cysternae, incluing the Sylvian and inter-hemispheric ones.