OBJECTIVE To study MR changes in the white matter of the brain in patients with breast cancer treated with a widely used protocol of high-dose chemotherapy and autologous bone marrow support. METHODS Thirteen patients with high-risk stage II or stage IV breast cancer treated with high-dose cyclophosphamide, cisplatin, carmustine, and bone marrow support underwent posttransplant MR examination of the brain. Serial posttransplant MR examinations were performed in 5 of the 13 patients and single MR examinations in 8. The severity of the white matter change was evaluated by two neuroradiologists and rated mild, moderate, or severe. RESULTS In 9 of the 13 patients, central and peripheral cerebral white matter changes were observed. Four patients had severe changes, extending from the ependyma of the lateral ventricles to the gyri. An additional 4 patients had moderate white matter change at the last observation. One had mild change, and 4 had no white matter change. In all patients, there was sparing of inferior frontal, posterior inferior occipital, and anterior temporal lobes, and of the centrosylvian brain. CONCLUSIONS White matter change occurred in patients treated with a high-dose chemotherapy and bone marrow support protocol. Most of the changes, and the more severe ones, occurred 5 or more months after the transplants. There was no apparent relationship between these changes and central nervous system function. Because of the increased longevity with this treatment, it is important to appreciate these white matter changes, recognizing however that their expression may be subclinical.