This paper stems from a region-wide audit of postoperative radiotherapy treatment for patients with screen-detected breast cancer, commencing from the start of the South Thames (East) screening programme in June 1988 and ending in March 1992. It reports on the variation in treatment practices amongst clinical oncologists in the region. There was diversity in treatment schedules, dose specification points, and the use of lymph node radiotherapy, breast boost and interstitial implants. While local protocols vary by centre and individual oncologist, many treatment decisions appear to have been dictated by the availability of machines and other resources. However, further analysis suggests that the variation is within the same range as that described in the nationwide survey of breast radiotherapy by the Audit Office of the Royal College of Radiologists in 1995 [1-3].