People with epilepsy may die unexpectedly without a clear structural or pathologic cause. This condition is called sudden unexpected death in epilepsy (SUDEP), and it accounts for a large proportion of deaths among people with epilepsy. SUDEP incidence rates vary with the cohort studied, ranging from 0.35 per 1,000 person-years of follow-up in population-based studies to 9.3 per 1,000 person-years in patients with refractory epilepsy. Although many studies have been performed, the causes of SUDEP are not understood. However, even without precise knowledge of the underlying pathogenic mechanism(s), SUDEP prevention could start with the identification of the most prominent risk factors. SUDEP seems to occur more commonly during sleep and it preferentially affects young adults with medically intractable epilepsy (especially tonic-clonic seizures), individuals who also have neurologic comorbidity, and patients receiving antiepileptic drug polytherapy. This article reviews the clinical features associated with SUDEP and suggests preventive measures for this condition.