In addition to ovarian ablation by means of surgery or irradiation, a wide variety of endocrine agents are now available for the management of breast cancer, in both the metastatic and adjuvant settings. Currently available endocrine agents include antiestrogens, progestational drugs, and aromatase inhibitors. Randomized trials and meta-analyses have greatly clarified the specific roles of the more established of these agents in both premenopausal and postmenopausal women. However the exact combination and sequence of these drugs are still under investigation. The addition of the bisphosphonates has also helped improve the quality of life of patients with metastatic disease. Among new endocrine agents currently under development are the pure antiestrogens, selective estrogen receptor modulators (SERMs), and a group of drugs with effects intermediate between the two.