In the field of oncologic surgery, an accurate local staging, i.e. the delineation of local disease extent, is considered of key importance to guide treatment decisions in patients with operable cancers, in particular patients who are operated on with curative intention. Imaging studies are used to provide a road map for the surgeon to help him or her obtain clear margins-which, in turn, is considered essential in order to avoid recurrent disease. It is well established that breast MRI is by far superior to mammography, with or without concomitant ultrasound, for the local staging of breast cancer. MRI allows the most accurate delineation of the size and the local extent of cancer, including the depiction of multifocal or multicentric or contralateral disease. MRI offers the highest sensitivity for demonstrating intraductal extensions around invasive cancers. Due to its very high negative predictive value, MRI can be used to confidently exclude the presence of breast cancer, and, thus, avoid unnecessary surgery. For all these reasons, MRI should be considered an integral part of the work up of patients who undergo breast-conserving treatment for breast cancer. And yet, the technique is only slowly adopted in clinical practice. Arguments against the use of breast MRI include costs, frequency of false positive diagnoses, lack of availability of minimally invasive biopsy capabilities, lack of evidence by randomized controlled clinical trials, and, last, fear of overtreatment. In this article, these concerns are explained, discussed and weighted against the advantages of pre-operative breast MRI for breast cancer staging. The point is made that breast MRI is essential for surgical planning, but that indeed unnecessary mastectomy may result if old guidelines are simply copied onto a new situation. Guidelines that require mastectomy for multicentric breast cancer have been established before the advent of MRI. Using the same guidelines to manage MR-detected multicentric cancer foci may be inappropriate because some small MRI detected additional multicentric breast cancer foci will be sufficiently treated by radiation therapy.