Twenty percent of the approximately 800,000 epileptic patients in Germany cannot be treated adequately by pharmacotherapy alone. According to conservative estimates, epilepsy surgery could be of fundamental therapeutic benefit to at least 10-25% of these patients. A complex presurgical diagnostic program is the basis for any epilepsy surgery. Numerous methods are used to create a hypothesis about the location and size of the epileptogenic area. In addition, before surgery is performed, it must be established that no additional serious neurological or neuropsychological deficits will result from the planned resection. For this purpose, electrostimulation of the cortex and temporary anaesthesia of brain areas by amobarbital tests are performed. In intractable epilepsy originating in the temporal lobe about 60% of patients become seizure free after surgery. Another 15-20% benefit from surgery by a significant improvement in their seizure situation. Resections of the dominant temporal lobe result in further impairment of memory functions in about 20-30% of patients.