With an ageing population, the number of older women with breast cancer eligible for adjuvant irradiation after breast conserving surgery and mastectomy is rising. There is a dearth of level 1 data on the effect of adjuvant irradiation on local control, quality of life and survival. In large part this reflects the exclusion of patients over the age of 70 years from randomised trials. The prevention of local recurrence may reduce the risks of dissemination. However, older women with early breast cancer and a life expectancy of less than 5 years are unlikely to derive a survival benefit from adjuvant radiotherapy. Rates of access of older patients to adjuvant irradiation are lower than for younger patients. Physician and patient bias and co-morbidities are contributory factors. There are also competing risks of mortality from co-morbidities, particularly in women over the age of 80 years. Postoperative radiotherapy after breast conserving surgery does not seem to compromise overall quality of life of older patients. Although the absolute reduction in local recurrence from adjuvant radiotherapy is modest in lower risk older patients after breast conserving surgery and adjuvant systemic therapy, there has to date been no group of fitter old patients defined from whom radiotherapy can be reasonably omitted. Guidelines for postmastectomy radiotherapy should not differ from younger patients. Adequately powered randomised trials are needed to assess the effect of adjuvant irradiation in older patients on outcomes after breast conserving surgery and mastectomy to provide a more robust basis for evidence-based radiotherapy practice.