It was already reported in else where that a standard linear accelerator, with only slight modification can function in a manner similar to Leksell's Gamma unit device in the treatment of inoperable deep seated intracranial lesions. Using collimated narrow beams, a localization system and special computer programs for precise patient positioning and a high concentration of irradiation dose within the lesions, eleven patients with AVMs and brain tumor have now been treated since 1988. The 6 MeV linear accelerator and Hitchcock stereotactic frame was used of the all procedures. In 10 of the 11 patients, no side effects occurred. The first 7 patients, who could be observed 3 months or longer have been studied radiologically and clinically. In 6 patients marked decrease in contrast enhancement and sometimes dramatic clinical improvement was achieved. In one case a marked increase of the surrounding brain edema occurred 7days after radiosurgery, who was operated on. The radiantion dose was based on the volume, location and radiosensitivity of the lesion which ranged 15-40 Gy.