Intraoperative electrocorticography(ECoG)is an important monitoring modality to delineate a focus area in cases with MRI-positive lesions. Previous reports have agreed on the usefulness of an intraoperative ECoG, especially in pediatric patients with focal cortical dysplasia. I will demonstrate a detailed methodology for intraoperative ECoG monitoring in the focus resection of a 2-year-old boy with focal cortical dysplasia who achieved a seizure-free outcome. Although the intraoperative ECoG has a distinct clinical value, it is associated with several issues, such as the focus area being decided by interictal spikes rather than seizure onset and being deeply affected by the anesthesia condition. Therefore, we need to keep in mind its limitation. Recently, interictal high-frequency oscillation has been recognized as an important biomarker in epilepsy surgery. Advancements in intraoperative ECoG monitoring are required in the near future.