Radiobiology has made great steps forward in the last five years in the development of new mechanisms forming the basis of various radiation effects, specifically among the mechanisms of low rate irradiation by low doses. Investigations of radiation apoptosis, radiation hormesis, radioadaptive response, and by-stander effects have been intensively developed. Processes of premature ageing induced by irradiation are examined. All these questions are discussed here. The greatest part is devoted to assessments of the health of the population irradiated inhabiting the radionuclide-contaminated territories and people from other regions of the former USSR involved in the liquidation on the accident consequences.