Patients with unilateral breast cancer are at increased risk of developing a second cancer in the contralateral breast. Some women choose contralateral prophylactic mastectomy (CPM) to prevent cancer in the contralateral breast. Several studies have demonstrated that CPM significantly decreases the occurrence of contralateral breast cancer. However, the effectiveness of CPM at reducing breast cancer mortality is not as clear. Moreover, CPM is not risk free and patients may need to undergo additional surgical procedures, especially if reconstruction is performed. Nevertheless, most patients are satisfied with their decision to undergo CPM. Alternatives to CPM include close surveillance with clinical breast examination, mammography and possibly breast magnetic resonance imaging. Endocrine therapy with tamoxifen or aromatase inhibitors significantly reduces the risk of contralateral breast cancer and may be more acceptable than CPM for some patients. The decision to undergo CPM is complex and many factors likely contribute to its use. Future prospective studies are critically needed to evaluate the decision-making processes leading to CPM.