A short review is given of the development of radiotherapy from its early beginning in 1896 to the establishment of the first three radium centres in 1913/14 which caused strong protest from the surgeons. The Radium Foundation was established on private initiative and was, via money collections, able to finance purchase of radium and in the 1930s erection of new buildings for the three centres. Radiotherapy became a basic specialty from 1950. In the beginning of the 1960s megavoltage therapy was introduced and at the same time chemotherapy was becoming interesting for therapy of solid tumours. This caused a centralisation of the patients to the centres for non-surgical therapy resulting in need for building of two centres (Aalborg and Herlev), and a gradual closing down of the decentral treatment with low voltage equipment in the counties. After 1970 the counties became responsible for the health care including running of the hospitals. This caused a return of some of the patients to decentral treatment facilities, usually the biggest hospital in the county and predominantly for adjuvant or palliative chemotherapy. The speciality has changed name to oncology in 1987.