One hundred years ago, Hilgartner used external radiotherapy for the first time in the treatment of retinoblastoma. This first case was published in the Texas Medical Journal in 1903. Immediate results were reported to be excellent but the long-term outcome was not known. The first documented cure of retinoblastoma over a long period of time was a case initially treated by Verhoeff (Boston) in 1917, with histopathological findings provided 71 years later by Marcus et al. at the patient's death. Henry Louis Hilgartner was born in 1868 in Baltimore and died in 1937 at the age of 69. His revolutionary treatment developed from the discovery of X-rays in 1895 by Wilhelm Conrad Röntgen and the parallel discovery of radioactivity by Henri Bequerel and Marie and Pierre Curie. In the sociopolitical context of 1903, Emile Loubet was president of France and this same year saw the Wright brothers' first motorized flight with the first power-driven heavier-than-air machine. The development of radiotherapy in the treatment of retinoblastoma can be divided into three distinct periods: an initial period of trial and error lasting from 1903 to 1928; a second period from 1929 to 1948 covering the introduction of calibrated radon needles up to the advent of external radiotherapy, and a third period, from 1948 to the present day, which can be considered a time of technical improvement and innovation. One hundred years ago, radiotherapy made a triumphant entry on the scene of retinoblastoma management. With our present knowledge of its side effects, we are now trying to remove it.