Neuroaxonal dystrophy is a feature of neuronal degeneration encountered in all subacute spongiform "virus" encephalopathies, including scrapie and Creutzfeldt-Jakob disease (CJD). By immunohistochemical techniques, the accumulation of 200 kDa neurofilament protein was demonstrated in affected neurites in murine CJD. These neurites exhibited the ultrastructural features of dystrophic neurites encountered in other neurodegenerative disorders, particularly Alzheimer's disease. These findings support the hypothesis that impairment of slow axoplasmic transport is a common pathogenetic mechanism for CJD and many other neurodegenerative conditions.