Epileptic encephalopathy with continuous spikes and waves during slow sleep (EECSWSS) is an age-related childhood condition characterized by epilepsy, cognitive or behavioral impairment, and electroencephalographic abnormality of continuous spike-wave discharges during slow sleep. Continuous spikes and waves during slow sleep (or electrical status epilepticus during sleep) is an electrographic pattern characterized by nearly continuous spike-wave discharges during non-REM sleep, with a frequency of 1.5-3 Hz and usually diffuse and bilateral in distribution. Most authors consider EECSWSS as wide spectrum of epileptic conditions of different origin associated with heterogeneous clinical manifestations and neuropsychological impairment of different severity in close temporal concordance with the appearance of the electroencephalographic pattern of electrical status epilepticus during sleep. The long-term prognosis of this condition is overall poor owing to the persistence of neuropsychological impairment. Therefore, early recognition and effective therapy are necessary to improve long-term prognosis.