The EEG was recorded using an endovascular guide wire as the electrode. This was Teflon coated except for its terminal portion, which was placed distal to the origin of the middle cerebral artery. Four hemispheres were sampled sequentially in two patients with intractable complex partial seizures who were undergoing routine preoperative carotid amytal assessment. Epileptiform spikes were detected in one patient, concordant with decreased hippocampal volume on MRI and scalp EEG changes. Endovascular EEG during the amytal procedure is less invasive than other intracranial EEG methods and may develop a role in preoperative assessment of selected patients with intractable epilepsy.