Background: The role of preoperative bilateral breast MRI in breast cancer patients being considered for breast-conserving therapy has been controversial. We hypothesized that preoperative MRI, along with an active program in MRI-directed biopsies, would lead to a change in multidisciplinary treatment planning for patients being considered for breast-conserving cancer therapy, and it would be associated with reduced rates of margin-positive partial mastectomies. Study Design: A retrospective review of a consecutive series of patients who were treated for breast cancer at a single center between January 2005 and July 2007 was conducted. Patients in the study were candidates for breast-conserving cancer therapy based on physical examination, mammography, and ultrasonography. All patients were evaluated by a preoperative breast MRI. Analysis included number and result of MRI-directed biopsies, impact of MRI on treatment planning, and incidence of margin-positive partial mastectomy within the series of patients. Results: Seventy-nine female patients were analyzed. Median age was 57 years. MRI led to the performance of 25 MRI-directed biopsies for previously unrecognized suspicious lesions in 21 patients. Forty-four percent of MRI-directed biopsies were positive for cancer. MRI was associated with a change in management in 15 patients (19%) for multicentric ipsilateral cancer (n = 7), a more extensive primary lesion size (n = 6), or contralateral breast cancer (n = 2). Incidence of margin-positive partial mastectomy requiring additional resective operation was very low in this series (10%). Conclusions: Bilateral breast MRI, when used in conjunction with MRI-directed biopsy procedures, can be helpful in planning multidisciplinary treatment of candidates for breast-conserving cancer therapy. By allowing more accurate local staging of tumors, MRI is a tool that can be used to help reduce high reexcision rates for margin-positive partial mastectomies. © 2008 American College of Surgeons.