Scrapie in sheep and goat is the prototype of the group of the transmissible spongiform encephalopathies which affect man and some animal species, notably other ruminants with bovine spongiform encephalopathy (BSE) and chronic wasting disease of wild ruminants. Transmissible mink encephalopathy (TME) is a rare disease of ranch-raised mink caused by exposure to a contaminated food ingredient in the ration scrapie, unrecognised BSE-like disease...). There is clinical and pathological similarities between TME and scrapie. These diseases share the following characteristics: a prolonged incubation period; a progressive, debilitating, neurological illness (always fatal); pathological changes confined to the central nervous system (vacuolisation, neurological loss, astrocytosis); the presence of scrapie-associated-fibrils (SAF) in brain tissue; and absence of detectable inflammatory or immune responses. The genetic origin of scrapie in sheep and the natural transmission of these spongiform encephalopathies are discussed.