Childhood skin haemangiomas have been subjected to many different kinds of active treatment. From the beginning of the twentieth century and up to 1960-1970, radiotherapy maintained a dominating place in this treatment, although during the latter part of this period its role was more and more questioned. Starting in 1958, I felt that, based on the scientific literature and on my own observations at Malmö University Hospital, active therapy including radiotherapy should be abandoned since it had turned out to be unnecessary and, furthermore, could be harmful. This viewpoint resulted from an increased knowledge of the natural history of the disease. I then got the possibility to establish a follow-up study cohort at Sahlgrenska University Hospital in Göteborg with the aim of gaining information on early and late radiation effects following childhood radiotherapy. Later, the study cohort was enlarged by pooling with similar cohorts originating from Stockholm and Paris. A summary of the results of the epidemiological studies is also presented here. This historical overview reflects half a century of radiation therapy and radiation protection philosophy. It contains a basic message pointing to the value of proper and reliable collection of medical data and to the importance of local, regional and national registers, to preserve the information.