Electrical status epilepticus during sleep (ESES) is primarily an EEG-defined syndrome in children characterized by the occurrence of continuous spike and slow waves during non-rapid-eye-movement (non-REM) sleep, the paroxysmal abnormalities being substantially less frequent during the awake state and REM sleep. Etiologically, cases can be divided into symptomatic and cryptogenic varieties. Partial motor seizures, frequently nocturnal, precede the emergence of ESES, whereas absence seizures often occur during the phase of ESES. The emergence of ESES is associated with neuropsychological regression. The characteristic electrographic pattern and epilepsy generally disappear during adolescence and are associated with an improvement in neuropsychological function. However, if the cases reported in the literature are representative, then there is a high probability of considerable residual dysfunction. A number of factors, broadly termed ascertainment biases, likely contribute to the paucity of reports from North America and the greater recognition of the syndrome in Europe and Japan. The current information on ESES is critiqued in this review.