Patient selection is an important consideration in breast-conserving therapy (BCT), and is dependent on the clinical and histologic determination of disease extent. In order to provide adequate local control without compromising cosmetic outcome, the amount of breast tissue that must be excised in BCT needs to be individualized. Nuclear magnetic resonance (NMR) imaging can provide better information than mammography or ultrasonography for assessing multifocal and multicentric disease in the breast. However, they will play a limited role in breast cancer staging until NMR imaging-directed sterotaxic biopsy becomes available. On the other hand, the histologic status of the surgical margins as well as certain features of the tumor including the presence of intraductal components is predictive of the extent of breast cancer. It is reasonable to evaluate and obtain clear margins when performing BCT. However, further investigation of new preoperative imaging and intraoperative staging modalities for assessing multifocal and multicentric disease is necessary.