Evidence is presented from a study of 680 patients followed over a period of 21 years that conservative treatment of breast cancer by local excision of the primary tumor followed by breast irradiation yields results equivalent to the traditional radical approach, with the added benefit of an excellent cosmetic result and improved quality of life. The relative survivals were 8.3% at 5 years and 71% at 10 years. There was no difference in survival when radiation was given. Breast irradiation significantly reduced relapse in the breast, but axillary irradiation did not influence relapse at this site. Relapse in the breast alone was not detrimental to survival if treated appropriately. Axillary relapse indicated a much poorer prognosis as might be expected.