Abstract: A method and apparatus for evoking epileptiform activity in patients with drug resistant epilepsy, as part of a presurgical evaluation procedure are disclosed. The apparatus includes a cranial helmet, for generating a DC magnetic field of a sufficient strength to evoke epileptiform activity, and means for localizing the regions of the patient's brain where said epileptiform activity has been evoked. In the preferred embodiment, the magnetic field strength varies between 1 milliTesla and 2 milliTesla, and is generated by two generally similar coils which are coaxially separated, and which are wound on corresponding thermoplastic members to form the helmet. The desired magnetic field strength is produced at about the middle of the distance between the two coils, in general registration with the hippocampus region of the brain. In an exemplary embodiment, the localizing means includes implantable Foramen Ovale electrodes for sensing the evoked and natural epileptic firings.