The prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of neurodegenerative diseases. They are caused by an abnormal form of a naturally occurring cellular protein, known as prion protein. All prion diseases are fatal and without cure. Although all are rare, interest has increased over the last 30 years due to the appearance of a new prion disease called variant Creutzfeldt–Jakob disease. This disease is transmissible via medical devices and blood. It therefore has implications for the anaesthetist, especially where blood transfusions and the use of airway devices and fibreoptic equipment are concerned.