Interstitial brachytherapy is a logical and attractive treatment for brain tumors. The ability to irradiate the tumor along with only a limited volume of surrounding brain and the increased therapeutic ratio allow the delivery of higher initial radiation doses and permit reirradiation of tumors that recur after conventional irradiation. The recent availability of CT-directed stereotaxic systems makes it possible to implant high activity iodine-125 sources into brain tumor target with great precision. The median survival of patients with recurrent malignant gliomas treated by brachytherapy was 74 weeks, which was longer than that of 36 weeks treated by chemotherapy.