Four anatomo-clinical cases of Creutzfeldt-Jakob disease (spongiform encephalopathy) are described. In 3 cases the correct diagnosis was made while the patients were living. The most important diagnostic elements are the following: rapid evolution of a presenile or senile dementia, with neurological symptoms unusual in the Alzheimer's disease. The importance of EEG for the diagnosis of Creutzfeldt-Jakob disease is confirmed: however the onset of the typical EEG abnormalities was very late in its manifestation, the CT alterations are in general absent or very limited. The pathological alterations are aspecific. The spongiform process was sometimes scarce or limited to specific cerebral areas.