Survival trends were reviewed among 12,641 women operated on for breast cancer at the Mayo Clinic from 1910 through 1964. Factors affecting survival among the 2,571 women operated on from 1955 through 1964 were analyzed. Axillary nodal involvement was the main determinant in survival; five- and ten-year survival rates were 86% and 72%, respectively, for patients without nodal involvement and 50% and 32%, respectively, for those with such involvement. When axillary nodes were not involved, survival after standard radical mastectomy was not much different from that after a modified radical procedure. When axillary nodes were involved, the data suggested that radical mastectomy might be associated with longer survival, but this remained unsettled. Postoperative irradiation did not influence survival, irrespective of axillary nodal involvement. Certain epidemiological aspects of breast cancer were reviewed from a community study (Olmsted County, Minnesota); survivorship changed only slightly, and specific incidence rates increased with age.