The combination of West syndrome (WS) and Down syndrome appears not to be coincidental. Fourteen patients free of cardiac malformation or history of perinatal hypoxia were referred and investigated before they had received any treatment and were followed to the mean age of 4.5 years (range 19 months to 14 years). Spasms had onset at the mean age of 8 months (range 4-18 months) in cluster and were symmetrical. Hypsarrhythmia was symmetrical and, after intravenous diazepam (4 patients, 0.5 mg/kg) it disappeared, without any remaining focus. Recorded spasms during a cluster were "independent," with recurrence of hypsarrhythmia between successive spasms, and thus had the ictal and interictal EEG characteristics of idiopathic WS. Seven patients exhibited other types of seizures after WS, consisting of myoclonic jerks, atonic, tonic-clonic or absence seizures, which proved quite easy to control with valproate and/or ethosuximide.