The neuronal ceroid lipofuscinoses (NCL), also known as Batten disease, are a group of inherited severe neurodegenerative disorders primarily affecting children. They are characterised by the accumulation of autofluorescent storage material in many cells. Children suffer from visual failure, seizures, progressive physical and mental decline and premature death, associated with the loss of cortical neurones. Six genes have been identified that cause human NCL (CLN1, CLN2, CLN3, CLN5, CLN6, CLN8), and approximately 150 mutations have been described. The majority of mutations result in a characteristic disease course for each gene. However, mutations associated with later disease onset or a more protracted disease course have also been described. At least seven common mutations exist, either with a world‐wide distribution or associated with families from specific countries. All mutations are described in the NCL Mutation Database (http://www.ucl.ac.uk/nclhttp://www.ucl.ac.uk/ncl).