A subgroup of patients with non-lesional temporal lobe epilepsy (NLTLE) have no evidence of hippocampal sclerosis (HS) on MRI or on histopathology. It is controversial whether this represents a different clinicopathological syndrome from NLTLE with HS, or whether both subgroups represent different ends of the spectrum of mesial TLE. Here the EEG source localization dipoles were compared between NLTLE patients with HS (HS+) and without HS (HS-), and the relationship with post-surgical outcome was investigated.