Have changing treatment patterns affected outcome for operable breast cancer? Ten-year follow-up in 1288 patients, 1965 to 1978. From 1965 to 1978, 1288 patients with primary operable breast cancer were treated by the senior author, using extended radical (ERM), radical (RM), and modified radical (MRM) mastectomy operations exclusively. Results were analyzed for trends in overall and disease-free survival, and patterns of local and distant relapse, the years 1965 to 1970 versus 1971 to 1974 versus 1975 to 1978. Significant changes (p less than 0.00001) from 1965 to 1978 included progressively earlier stage of disease, less frequent use of RM and ERM, a decline in the use of postoperative radiotherapy, and the introduction in 1975 of multidrug adjuvant chemotherapy. Ten-year disease-free survival rates improved significantly for all patients (by 11%, p = 0.00004) and for node-negative (by 12%, p = 0.0024), node-positive (by 8%, p = 0.012), clinical stage II (by 15%, p = 0.0022), and pathologic stage II (by 12%, p = 0.016) disease. Ten-year local recurrence for all patients was 3% (local only) and 2% (local with distant metastasis), and survival from date of recurrence for all patients failing treatment increased two times (p less than 0.0001) for patients treated most recently. As the primary surgical treatment of breast cancer continues to become more moderate, the promise of systemic adjuvant therapies can be realized only with continued emphasis on earlier diagnosis and maximal local control of disease. 