[en] The harm that might be caused by radiation exposure was recognised within months of Rontgen's discovery of X-rays, and recommendations for protection of patients and workers with radiation were formulated first in 1928. In the light of increasing radiobiological, genetic and human epidemiological evidence, it became clear that there might be no threshold, below which harmful effects did not occur. Recommendation and practice in radiation protection reflected this opinion from the early 1950's, and emphasised the consequent need for minimising exposures, quantifying risks and revising the dose limits appropriate for internal radiation of body organs. (author)