Since 1997, researchers in the UK have searched for variant Creutzfeldt-Jacob and other diseases that cause progressive intellectual and neurological deterioration (PIND) by sending a monthly surveillance card to UK pediatricians. Clinical details are obtained by questionnaire or site visit. In 12 years, 2636 patients <16 years old with suspected PIND were reported, of whom 1114 had a confirmed diagnosis. Of 147 different diseases, the 6 commonest groups were leukoencephalopathies (183 cases), neuronal ceroid lipofuscinoses (141), mitochondrial (122), mucopolysaccharidoses (102), gangliosidoses (100), and perixisomal diseases (69). Districts having high rates of consanguinity reported relatively large numbers of PIND cases. Only 6 children with variant Creutzfeldt-Jacob disease were identified.