This clinical guideline updates and replaces NICE clinical guideline 20, published in 2004. It also updates and replaces NICE technology appraisal 76 (2004) and NICE technology appraisal 79 (2004). It offers evidence-based advice on the care and treatment of children, young people and adults with epilepsy. New recommendations have been added for the pharmacological treatment of people with epilepsy, including the use of ketogenic diet.