It has been twenty-five years now since the accident occurred at the Chernobyl nuclear power plant. In the early days after the disaster, it was difficult to assume that its aftermath would make itself felt after a quarter of a century. Numerous studies in Ukraine, Belarus and Russia have shown that the morbidity of a number of diseases among the exposed population, liquidators and children residing in the contaminated areas has increased several times after the accident. Particular attention is drawn to health conditions of the children who were exposed to radiation and the children of liquidators who also demonstrate ill health. This book examines the need for further development of radiobiological and radioecological research, increase in the availability of methods, development of novel theoretical risk models and new approaches to investigating into the complex processes that occur at present and are expected in the future.