Increasing experience with magnetic resonance imaging (MRI) has raised important questions about how it should be used in breast cancer screening, and for presurgical evaluation and posttherapy follow-up of women with this disease. Overall, the availability of MRI as an adjunct to mammography and ultrasound offers clear clinical benefit to women at increased risk of breast cancer development due to BRCA1 and BRCA2 mutations, and to women presenting with axillary adenopathy and an occult primary breast tumor. In contrast, its benefit for routine selection of breast conservation or further assessment of lobular carcinoma in women of average risk has not been demonstrated. This article reviews the use of MRI in these settings, with an emphasis on the clinical outcomes that have been observed to date.