A retrospective analysis was conducted of 9 children with focal cortical dysplasia and localization-related epilepsy who underwent epilepsy surgery. Focal cortical dysplasia includes malformed lesions with extensive abnormalities of neuronal morphology, architecture, and lamination. The patients were examined by EEG and video EEG telemetry, CT, MRI, and SPECT using 99mTc-HmPAO. EEG disclosed interictal localized epileptiform activity in 8 patients and nonepileptiform activity with slow waves in 1. Ictal EEG telemetry demonstrated a predominantly localized seizure onset in 8 patients and MRI demonstrated an abnormal loss of gray and white matter distinction in 6. Decreased regional cerebral blood flow (rCBF) was detected in 4 patients by interictal SPECT, and increased rCBF in the same epileptogenic focus in 2 by postictal SPECT. Pathologic analysis found focal cortical dysplasia in 8 patients. One had extensive focal polymicrogyria, pachygyria, and extensive white matter heterotopias. It is concluded that MRI can detect focal cortical dysplasia, which corresponds to the epileptogenic focus on EEG, and SPECT may help to detect a functional abnormality in the same region.