For correct radiation treatment and evaluation of treatment a complete recording of data is necessary. With this aim an interactive system was developed. Data recording for every patient is started from a terminal assigned to the physician. After completing the patient file with the data of the physical treatment plan, the file may be displayed on the terminal assigned to the particulr treatment unit, and additional data of the particular treatment session added. If a treatment is finished, a hardcopy of all data is generated by the system. Retrieval of patient data is always possible from the physicians terminal. The system is a contribution towards reducing the work in documentation the radiation treatment. It will be possible not only to carry out epidemiological studies, but also to investigate and perhaps optimate the results of treatment methods.