Neoadjuvant endocrine therapy is becoming increasingly popular as a safe and effective alternative to chemotherapy in selected patients. Large randomized studies have been published comparing tamoxifen with steroidal and nonsteroidal aromatase inhibitors, with favorable results for aromatase inhibitors letrozole, anastrozole, and exemestane. Endocrine therapy can be used in the neoadjuvant setting for conversion of inoperable breast tumors to operable, and from potential mastectomy to breast-conserving surgery. The use of endocrine agents in this setting also provides an opportunity for the study of their biological effects upon tumor.