An account is given of six cases of Jakob-Creutzfeldt disease confirmed at necropsy. The rapid fatal outcome within three months was typical of the variety designated subacute spongiform encephalopathy (Nevin-Jones). The characteristic EEG changes were found to be of great value in making an early diagnosis and, together with akinetic mutism and myoclonus, constituted an easily recognizable picture. Treatment with idoxyuridine was ineffective in one case in which electronmicroscopy of brain biopsy material supported the diagnosis.