The appearance of bovine spongiform encephalopathy (BSE) followed by new spongiform encephalopathies and variant Creutzfeldt-Jakob disease (CJD) in the United Kingdom indicates that these diseases may be linked. To give an understanding of this risk, the authors review the literature on the pathogenesis of CJD and BSE and the current findings on how these diseases are transmitted. They also discuss the implications for Canada's food and blood supply and outline previously published recommendations for disease prevention.