The morphofunctional state of hemopoiesis in patients who suffered from the Chernobyl accident was investigated. The activation of proliferative activity of erythroid progenitor cells simultaneously with a decrease in the resistance of erythrocytes and an increase in the levels of methemoglobin, HbF, and an increase in the number of HbF-containing cells in peripheral blood were detected. Main trends in the development of adaptative processes in the erythron system as a response to affect of low doses of radiation were determined on cellular and molecular levels.