The use of interictal and ictal electroencephalography (EEG) for the definition of the Epileptogenic Zone and thus of a possible epilepsy surgery in patients suffering from a focal drug-resistant epilepsy, has always been and is still, crucial. The presurgical procedures should be adaptable and tailored to individual cases, adding to the anatomical neuroradiological and clinical data to construct the mandatory anatomical-electro-clinical correlations. In the simplest, mostly lesional cases, interictal scalp EEG may be adequate, rising to the complexity of patients with negative Magnetic Resonance Imaging (MRI) or complex malformations of cortical development, who require surface recording of ictal manifestations and a subsequent monitoring with invasive explorations. There are no comprehensive guidelines on good clinical practice for both Video-EEG and invasive investigations, leaving it to the experience of individual centers to choose the criteria for selecting and carrying out the investigations deemed indispensable.