Without electronic data processing the recording and statistical evaluation of a great number of tumor patients is only hardly possible. A tumor register and follow-up program is described which has been established for radiotherapy during the development of a national tumor register organized at present. This tumor register also serves as a basis for letter-writing to physicians. The software can easily be adapted to the needs of every hospital because a commercial data bank system has been used. The data input and output is carried out over several terminals. The hardware and software system as well as the incorporation of the data bank into the national tumor register are described.