This chapter explores the technical and clinical aspects of intracranial electroencephalography (iEEG) for epilepsy surgery. Focal interictal epileptiform discharges (IEDs) indicate areas of excitatory post-synaptic potential imbalance, and intracranial recording is crucial for accurate localization of epileptogenic zones that may not be evident on scalp EEG. We discuss electrode types, including subdural strips and grids, epidural and depth electrodes, and stereotactically placed SEEG electrodes, examining their utility across various brain regions. Intraoperative electrocorticography (ECoG) aids in determining resection boundaries by identifying epileptogenic regions during surgery, while extraoperative iEEG provides extended monitoring, often needed in non-lesional or complex epilepsy cases. Detailed discussion covers the methodology, electrode types, anesthesia, and potential complications. Three case studies illustrate how iEEG and ECoG guide resections and confirm functional zones, such as language and speech areas, enhancing outcomes by identifying seizure onset zones precisely. Advanced techniques like SEEG-guided radiofrequency thermocoagulation offer alternative treatments when resective surgery is not possible. This chapter aims to underscore iEEG’s critical role in achieving seizure freedom through precise mapping, optimizing surgical decisions, and reducing patient morbidity.