In this satellite symposium several validation studies of automated interictal ESI are presented. We will then move on to discuss interesting cases that illustrate the value of interictal ESI in the preoperative work-up. The last part of the symposium is dedicated to the localization of ictal EEG. Ictal ESI is the new frontier of advanced EEG analysis in the preoperative work-up, and may allow localization of the seizure onset zone rather than the irritative zone. We will discuss how new analysis techniques enable electrographic seizure localization and their validation status.