The approach to primary operable, or potentially curable breast cancer is a controversial field of oncology and is subject to a number of ongoing clinical experiments in many centers. This report discusses the recommended treatment for patients with this disease who are evaluated at the Breast Service of Memorial Sloan-Kettering Cancer Center. The most widely practiced treatment is modified radical mastectomy, with radical mastectomy reserved for patients having more advanced lesions. Modified radical mastectomy is defined as total mastectomy plus axillary lymph node dissection either with preservation of the pectoralis minor muscle or its removal. The latter allows a more thorough axillary dissection and is preferred for patients with invasive carcinomas. In either case, axillary node sampling is not advocated and will miss a significant percentage of axillary metastases. In patients with negative axillary lymph nodes, who are not candidates for adjuvant systemic therapy, breast reconstruction is possible within a few months of mastectomy. For patients with involved axillary nodes, trials of adjuvant chemotherapy (perhaps with antiestrogen therapy for estrogen-receptor positive primary tumors) seem to offer the best hope for improved survival. With available follow-up of such trials to date, there seems little doubt that at a minimum, such treatment prolongs disease-free interval. The role of adjuvant radiation therapy is more controversial, and the difficulty in combining this with chemotherapy is apparent.