Patients with high-grade primary and metastatic brain malignancies have a median survival time of 3-8 months, regardless of therapy. Because MagnetrodeTM hyperthermia provides safe, deep internal heating without normal-tissue injury, we studied its effects first on the brain and surrounding tissues of rabbits. The normal rabbit brain (n = 26) could be heated to potentially tumoricidal temperatures (42-43 degrees C) without apparent histopathologic or clinical damage to the brain, skull, external eye, subcutaneous tissue or skin. Intracranial pressure did not rise significantly. Using transplanted VX-2 carcinoma, we showed both the safety and potential efficacy of thermochemotherapy (IV BCNU: 14 mg/kg) in the presence of a solid brain tumor. The average maximum brain temperature achieved was 43.06 degrees C. Mean survival from the time of tumor implantation in the treated group (n = 16) was 18.56 days, compared to 9.3 days for untreated controls (n = 30) (p less than .0001). Two patients have been treated with localized brain hyperthermia combined with intravenous BCNU (80 mg/m2) for a total of eight treatments. Maximum normal brain temperature achieved was 40.0 degrees C in Patient #1 and 41.5 degrees C in Patient #2. A tumor temperature of 42.9 degrees C was achieved in Patient #2. Intracranial pressure remained within the upper limits of normal. Swan-Ganz monitoring in Patient #1 revealed a stable cardiac index and mean pulmonary artery pressure with mild fluctuations in the CVP, PAD, and PCW. No increase in chemotherapy toxicity was observed and no normal tissue injury occurred in either patient. We conclude that non-invasive localized radiofrequency hyperthermia to the brain is feasible and can be performed safely in the presence of a solid brain tumor.