If we consider the development of any specialization in our region in an historical context, we cannot separate the Czech and Slovak Republics. The 75 years together (with the exception of 1939-1945) were a period of narrow cooperation between Czech and Slovak Universities and Scientific Institutes, and Radiobiology is no exception, which is why the discussion falls to Czechoslovak Radiobiology, as opposed to Czech Radiobiology alone. Czechoslovak Radiobiology has gone through three important stages in its history, influenced also by international political-military situations. Here it is necessary to emphasize that the results obtained by Czechoslovak Radiobiology were and are comparable with foreign institutions. The first period, which dates back to 1895-1939, represents the initial discovery period of the mechanism and consequences of ionizing radiation on the body. The second period in 1939-1990 is considered to be the phase of peaceful uses of nuclear energy, their misuse for military purposes, along with detailed studies of radiation sickness and radiation protection, the majority of the results which were kept secret and could not be published at the time. The third period after 1990 is dedicated to the detailed study of post-radiation changes at the intracellular level with the aim to be used especially in radiotherapy and radiation protection, as well as the dangers of misuse of ionizing radiation by terrorists. Increased attention is also devoted to the effect of ionizing radiation on plants and their possible subsequent use.