Ovarian ablation has been used for breast cancer treatment for nearly 100 years. Available methods of causing ovarian failure include surgical or radiotherapeutic ablation and LH-RH agonists that effect a reversible "medical oophorectomy." In addition, administration of certain types of chemotherapy to susceptible hosts may also result in permanent amenorrhea. The response rate to ovarian ablation in premenopausal women with metastatic breast cancer is about 35%. It is more effective in women over 35 years of age or with estrogen receptor-positive tumors. Oophorectomy, ovarian radiation, and luteinizing hormone-releasing hormone agonists are probably equally effective in this setting, although rigorous comparative trials have not been completed. Individual trials of ovarian ablation as adjuvant therapy show a trend toward increased relapse-free survival, but rarely show a survival advantage. However, an overview analysis of randomized trials of adjuvant ovarian ablation, which includes about 1800 women under 50 years of age, suggests that this modality reduces the annual rates of recurrence and death by about 25%, an effect similar to that seen with adjuvant chemotherapy by indirect comparison. Therefore, a number of clinical trials designed to elucidate the role of ovarian ablation alone or in conjunction with other adjuvant approaches are in progress. The routine use of ovarian ablation as an adjuvant therapy should await the establishment of its efficacy in these trials.