: Breast-conserving surgery is the preferred operation for the majority of women with stage I or II breast cancer. It consists of the removal of primary breast cancer with a rim of adjacent normal tissues and the axillary dissection. The goal of breast-conserving surgery is to control the local-regional disease without removing the entire breast and to provide an accurate pathologic staging of the tumor (T) and draining nodes (N). The primary outcomes of breast-conserving surgery in treating women with invasive breast cancer are measured by the survival rate, local disease control and cosmetic results. The consideration of the factors that have major impacts on the outcomes of this form of treatment are discussed. This article provides a framework for considering and performing breast-conserving surgery and for critically evaluating the literature dealing with the various issues involved in the treatment of women with early breast cancer.