This multicenter study, which is based at UCSF and is funded by the National Institutes of Health and the Elekta Corporation, is the first of its kind in the United States. A small number of patients have been successfully treated with a similar protocol in France. The study will randomize 40 patients into two dosage groups and monitor several clinical and radiological characteristics over three years following radiosurgical treatment. These will include the effect on seizures, magnetic resonance (MR) imaging (including diffusion- and perfusion-weighted studies), MR spectroscopy, and neuropsychological outcomes. In addition to possibly establishing a new, noninvasive way to treat temporal lobe epilepsy, this study will help define the mechanisms of how radiation helps control epileptic seizures. The study began in the fall of 2000 and as of 03/03 is still accruing patients. For information, contact Principal Investigator Dr. Nicholas Barbaro by calling 415.353.7500.