The specialty of radiotherapy has changed rapidly over the past two decades with the development of more sophisticated planning and delivery techniques. These techniques have made it possible to increase safely the radiation dose to the tumour while limiting the dose to surrounding healthy tissues that are sensitive to radiation. Here, we focus on clinical improvements that have been achieved with technological advances in the planning and delivery of radiotherapy and look at the potential for future improvements. It should be noted that improved understanding of the biology underlying the radiation response and the use of chemotherapy and molecularly targeted therapy to enhance radiation sensitivity have contributed equally to the improved outcome of patients undergoing radiotherapy.