In 1994, late effects of radiotherapy should be limited to an acceptable rate of benign and non-disabling complications. In almost all cases, this goal can be presently reached, owe to recent technological and radiobiological advances. The precise adaptation of irradiated volume, dose, fractionation and total duration of treatment should avoid severe post-radiotherapeutic toxicity. The identification of subgroups of patients with high susceptibility to ionizing radiations should soon allow the radiotherapists to take up the challenge of a both efficient and non-toxic irradiation.