Six children affected by tuberous sclerosis and severe multifocal epilepsy were studied by MRI. In all cases, MRI disclosed multiple cortical lesions and the relationship between these lesions and the EEG localization of epileptogenic foci has been studied. In all cases, a relationship between the localization of persistent EEG foci and the site of the major MRI lesions was found. The presence of frontal cortical tubers, mainly localized in the parasagittal region, was related to more intractable seizures.