An increased incidence of late rectosigmoid complications, with no improvement in local control, was observed after the introduction of a 6 week technique of external beam pelvic irradiation (55.0 Gy in 30 fractions) in Edinburgh. This increase in morbidity did not appear to be related to the use of a single intracavitary caesium insertion or to the introduction of a Selectron for remote afterloading. A 5% dose reduction was subsequently instituted.