Though the role of cerebral ischemia as an etiologic factor for epilepsy is accepted, the effect of seizures on stroke sequelae has received little attention. We describe 10 patients with poststroke partial epileptic seizures that were followed by persistent worsening of the previous neurologic deficit. Of 38 other patients with poststroke seizures who were examined during the same period, eight suffered transient neurologic worsening (Todd's phenomenon). Persistent worsening was associated with longer seizures and longer partial seizures before generalization. Risk factors, age, sex, other seizure features, and characteristics of previous stroke were irrelevant to developing persistent worsening of stroke sequelae. None of the patients with persistent worsening showed a new lesion or an extension of the previous ischemic area on computed tomography or magnetic resonance imaging, except one who had a first hemorrhage that spared the cortex and who suffered a second hemorrhage, which was lobar. Persistent worsening of a neurologic deficit following a seizure in patients with previous stroke may not be uncommon and may be due to a direct effect of the seizure itself on the infarcted area.