This article reviews the development and potential impact of Digitally Reconstructed Radiographs (DRR's) in the planning and verification of radiotherapy treatments. It explores the requirements for the creation of usable DRR's their integration into current verification methods and it highlights some of the factors that may influence the routine use of DRR's. Continuing developments in radiotherapy techniques demand increasingly accurate verification methods. DRR's provide an efficient and effective representation of planned treatments for comparison with both simulator and portal images, encompassing the digital imaging technology which is the future of radiotherapy treatment verification.