In Alzheimer's disease, the most prevalent of the neurodegenerative diseases, inflammation of the CNS contributes to the pathology and is a target for therapy. [13, 18, 19]In contrast, the group of neurodegenerative conditions known as the Prion Diseases have been widely reported as lacking any inflammatory elements [5, 23]despite the many similarities between the pathologies of Alzheimer's Disease and Prion Diseases. [10]We have found evidence for an inflammatory component in mouse scrapie, characterized by microglial activation and T-lymphocyte recruitment, which appears long before any clinical signs of the disease and spreads along well-defined anatomical pathways. These observations emphasize the potential value of murine scrapie as a model for studying the inflammatory pathology of other neurodegenerative diseases. Copyright © 1996 IBRO. Published by Elsevier Science Ltd.