Bovine spongiform encephalopathy (BSE) has become the most publicly recognizable example of a group of fatal neurodegenerative diseases caused by proteinaceous infectious particles called prions. The contributors to this volume, all internationally recognized experts in their fields, provide an introduction to prion biology, followed by reviews of the latest information on BSE, vCJD, and chronic wasting disease, an animal prion disease that has recently emerged in North America.