Using individual body cross-sections for purposes of irradiation (obtained by computed tomography with the Siemens-Somatom) in combination with a system for treatment planning (TPS, Phillips), a marked improvement of irradiation planning is achieved. Thus, an advance in the quality of radiation therapy may be expected. Some inconvenience with this combination of instruments, due to the necessity of enlarging the CT cross-sections up to life-sized cross-sections suitable for the TPS, is unavoidable so far.