The present status of endocrine therapy for breast cancer was reviewed from the surgeon's point of view. Endocrine ablation therapy, such as oophorectomy, adrenalectomy and hypophysectomy, has been frequently used for the advanced breast cancer patients. More recently, however, major endocrine ablation therapy has been less the treatment of choice for advanced breast cancer, because an antiestrogen (tamoxifen) which is less toxic has been prevailing in the treatment. It was shown that after the breast cancer became refractory to tamoxifen, the major endocrine ablation therapy was effective particularly in ER (+) cancers, irrespective of the response to the antiestrogen. This suggests the significance of major endocrine ablation therapy as a second line therapy for advanced breast cancer patients. The adjuvant endocrine and/or chemotherapy for operable breast cancer patients was reviewed, with special reference to the ovarian failure due to endocrine or chemotherapeutic agents. A prospective randomized study of endocrine and/or chemotherapy for the adjuvant of mastectomy stratified by the presence or absence of ER in breast cancer tumors, has been performed in our hospital. Patients with ER (+) breast cancers were divided into 3 groups: 1) tamoxifen 20 mg/day for 2 years (in premenopausal status, after oophorectomy), 2) chemotherapy with mitomycin C 20 mg/m2, iv, followed by administration of cyclophosphamide 60 mg/m2, po, 3) combination of tamoxifen and the chemotherapy. The chemotherapy alone or combination of chemotherapy and tamoxifen was given patients with ER (-) cancers. At September, 1983, 422 patients took part in the trail, and the median follow-up period was 33 months (at least 9 months). The recurrence rate of the group treated with antiestrogen alone was shown to be similar to that in other treatment groups in ER (+) cases.