The temporal behavior of neonatal seizures caused by diverse acute encephalopathies in 42 patients with 487 seizures was studied. All 487 seizures were confirmed by typical ictal electroencephalogram (EEG) patterns. Neonatal seizures are relatively brief events, which usually last about 2 min. They are recurrent and are separated by interictal recovery periods of variable duration, on the average, about 8 min. Solitary prolonged seizures are rare and do not represent the usual behavior of neonatal seizures.