In 1986, a new neurologic disease appeared in the Great Britain's Cattle. According to its histological lesions, this condition belongs to the group of transmissible encephalopathies known as spongiforme encephalopathies (SE). These SE are associated with no-conventional transmission agent (NCTA) or Prion. At the time of writing, over 13,000 cases of Bovine spongiforme encephalopathy (BSE) have occurred in UK. The most likely origin of this dramatic outbreak would be an oral contamination of Cattle by the feeding of sheep carcasses or of all infected with scrapie, another SE, incorporated to concentrates. Possible factors as changes (lower temperatures and reduced use of organic solvents to extract fats) in the rendering process could have preserved the very resistant Prion in these concentrates. The important lessons resulting from our present knowledge and hypothesis are there would be no species barrier to impede transmission of the NCTA through oral route. The question concerns the public health risks posed by BSE. Two related diseases of human are Kuru and Creutzfeldt-Jacob disease. At the present time, based upon epidemiological datas on scrapie, BSE is unlikely to be a major threat to humans. Nevertheless, precautionary steps to reduce a potential risk to an absolute minimum were taken by British regulations and more recently, by European directives.