Systematic epidemiological surveillance of Creutzfeldt-Jakob disease was carried out in England and Wales covering the years 1970-1984. The results of this work provide a basis from which to assess any change in the pattern of Creutzfeldt-Jakob disease following the occurrence of Bovine Spongiform Encephalopathy. The methodology, early results and problems of the current systematic national survey of CJD, initiated in May 1990, are discussed.