This book introduces the applications of intracranial electrode electroencephalgram (EEG) for locating epileptic foci. In each representative case, it includes the patient's scalp EEG and intracranial EEG, and provides more detailed information on the patient's medical history, surgical plan decision and follow-up. In addition, to facilitate understanding, a short commentary and analysis is attached after each case. It is a useful reference for epilepsy practitioners to combine the medical history, seizure symptom characteristics, scalp EEG and seizure phase video results to develop intracranial electrode implantation plan.