In the last several years there has been a renewed interest in interstitial brachytherapy for the treatment of both newly diagnosed and recurrent malignant gliomas and solitary cerebral metastases. A variety of techniques are currently in use for the planning and stereotactic implantation of radioactive isotopes into these tumors. Although there seems to be strong evidence to support the use of this technique for recurrent malignant gliomas, further work is needed to confirm its efficacy in an adjuvant setting for treating of newly diagnosed tumors and to determine the effect of the addition of hyperthermia or chemotherapy on outcome.