Mortality in people with epilepsy is two- to three-times that of the general population. This can be attributed to epilepsy itself (epilepsy-related death) or to the underlying cause of the epilepsy. Sudden unexpected death in epilepsy (SUDEP) is the commonest cause of epilepsy-related death. It is a syndrome where a person with epilepsy dies suddenly and no other cause of death is found. There are frequent reports of persons dying alone in their sleep. It is assumed that death occurs following a seizure but since the deaths are often unwitnessed this is only an assumption. The most important risk factor appears to be poor seizure control. Lately, SUDEP has received much public interest, has been the subject of international forums, ethical debates and comprises part of national guidelines on epilepsy management. Despite its high profile, the evidence for specific risk factors and pathophysiology is still not established. Poor incident case reporting, inaccurate death certification and fewer post-mortem examinations have limited the value of epidemiological data on SUDEP. Here, we review the characteristics of SUDEP, its likely risk factors, mechanisms and differential diagnosis, and consider possible strategies for prevention. We also explore the discussion of SUDEP with patients and the management of relatives of SUDEP patients.