Magnetic resonance (MR) imaging has high sensitivity in detecting and determining the extent of breast cancer and the information provided by this modality has proven valuable in patient management. Investigations defining the strengths of MR imaging, technical advances, and greater standardization of protocols have led to its increased use in patients with breast cancer, both before and following treatment. This article reviews techniques and procedures used in the performance and interpretation of breast MR examinations. Applications of MR imaging in the management of patients with breast cancer are also summarized, including preoperative evaluation of extent of disease, postoperative assessment of residual disease, and the detection of recurrent carcinoma. The use of MR imaging to evaluate patient response to chemotherapy and to assess patients with axillary lymph node metastases with an unknown primary lesion will also be discussed.