It seems unlikely that anyone could have foretold the interest, controversy, and concern that the occurrence of bovine spongiform encephalopathy (BSE) in cattle in Great Britain would cause when the author was commissioned to investigate its epidemiology in the spring of 1987. The epidemic has proved to be the largest food-borne epidemic of a transmissible spongiform encephalopathy (TSE), and has been the subject of detailed scrutmy epidemiologically, by international agencies and governments, and by representatives of all types of media worldwide. During the course of the epidemic an attempt has been made to decipher the epidemiology of BSE with the usual objectives, the most important being to provide a model of causation such that necessary statutory controls could be identified and enacted to protect animal and human health, both in Great Britain and abroad.