Sudden unexpected death in patients with epilepsy (SUDEP) has been recognised since the first part of the 20th century. Epilepsy has been defined as a disorder of the brain characterised by an enduring predisposition to generate epileptic seizures and by neurobiological, cognitive, psychological and social consequences of this condition. The International League Against Epilepsy (IALE) produced a practical clinical definition of epilepsy in 2014. The incidence of SUDEP is clearly going to depend upon accurate classification of deaths in patients with epilepsy and this will thus depend upon the thoroughness of death investigation, including how detailed the post-mortem examination is conducted. Seizure activity affects both respiration and cardiac activity. Central-mediated apnoea has been observed in seizure activity. Sudden unexpected death following a previous head injury potentially introduces the possibility of death linked to the head injury if there was a history of post-traumatic seizures.