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Twenty-five patients (aged 3 to 39 years) were anesthetized with methohexital for electrocorticographic mapping and resection of epileptogenic foci. These patients have been compared with 11 patients (aged 11 to 40 years) who had the same surgical procedure performed while they were awake because their epileptogenic foci were near the speech or motor areas. All patients received morphine and droperidol to produce analgesia and sedation, and a field block was established with local anesthetics. In the 25 patients, general anesthesia was induced with methohexital, 1.5 mg/kg. and maintained with a 0.1% infusion. After intubation, ventilation to a PaCO2 of 30 mm Hg was maintained with O2/air. A resectable abnormal electroencephalogram focus was localized in every case. All but two of the patients awoke promptly in the operating room, allowing extubation and participation in neurologic assessment. None remembered the procedure. The incidence of improvement of seizures in patients given methohexital was similar to that in patients who had surgery while awake. Unlike many general anesthetics that depress epileptogenic activity, methohexital activates seizure activity and can therefore be used for the dual purpose of producing general anesthesia and enhancing electrocorticographic delineation of epileptogenic foci.