Neonatal findings and evolutionary courses of epileptic seizures were described in newborns who had seizures during the neonatal period and later developed epilepsy. Neonates with CNS dysgenesis ran the highest risk (80%) for subsequent epilepsy. About 30% of those who suffered from perinatal hypoxia and/or intracranial birth injury and 30% of those who had meningitis developed subsequent epilepsy. In perinatal brain injury, those who developed epilepsy showed more abnormal neurological and electroencephalographic findings than those who did not. The more abnormal the neonatal background EEG, the more frequently epileptic fits developed later. There was no such relationship in CNS dysgenesis. Myoclonic seizures were associated with the most severe brain damage. Newborns who later displayed West syndrome had also very abnormal neonatal EEG whereas those who manifested other types of fits more often had less abnormal neonatal EEGs. In West syndrome, hypsarrhythmia was preceded by focal or multifocal spikes, and closely temporally related with the onset of spasms, but there was a variety of intervals between the onset of clinical fits and EEG spikes in generalized or focal motor seizures.