To investigate the epileptogenic foci in dysembryoplastic neuroepithelial tumor (DNT) in the temporal lobe, we studied extraoperative electrocorticography (ECoG) with subdural electrode arrays from nine patients with intractable epilepsy due to temporal DNT. Ictal onset zones and irritative zones were decided by the ECoG. The locations of these zones were compared to the location of the tumor. The number of ictal onset zone and irritative zone was 2.1±0.93 and 2.9±.45 in a patient with a DNT. They were detected more frequently in the adjacent tissues of the tumor (88.9%) rather than within the tumor or in mesial temporal area (66.7%). Mesial temporal involvement was found in 6 patients (66.7%) as an ictal onset zone, and in 5 (55.6%) as an irritative zone. The 7 patients (77.8%) had ictal onset zone in areas different from active irritative zone. The surgical outcome was better, when ictal onset zone was completely resected rather than partially removed. Temporal DNT can make multiple ictal onset zones and irritative zones in different regions including the mesial temporal area. Deliberate resection of epileptogenic foci, including all ictal onset zones and irritative zones, ensures excellent seizure control.