Electroencephalographic seizures were evaluated in 112 neonates. The first portion of the study involved 80 neonates with clinically identified abnormal movements, 8 of whom (10%) had electroencephalographic evidence of seizures coincident with this activity. Patients with abnormal movements (90%) had no concurrent electrical seizures. In the second part of the study, 40 infants who had electrical seizures were investigated. Eight of these infants had been identified during the first part of the study. Two-thirds of the patients (25) were premature. Sixteen patients (40%) died; 90% had brain lesions documented by computed tomography and/or postmortem study. Cerebral infarction and intraventricular hemorrhage were the most common lesions. One-third of the survivors (8 of 24 patients) were normal at a mean age of 3 years, while two-thirds had significant neurologic and developmental abnormalities. Neonatal seizures often are subtle, not associated with observable clinical expression, and associated with adverse development. Electroencephalographic confirmation is important in the evaluation of neonatal seizures.