He contributed extensively to experimental hematology by elucidating the cellular kinetics of normal and leukemic hemopoietic cell renewal using tritiated thymidine and single cell autoradiography. He also contributed extensively to the analysis of the pathophysiology of the acute and chronic radiation syndromes. Dr. Fliedner and his group paved the way for the characterization, physiology and pathophysiology of hemopoietic stem cells in the peripheral blood and to their mobilization, collection, cryopreservation and utilization for hemopoietic reconstitution after total body irradiation both in the canine model and, in the early 1980s, in human beings (in collaboration with the University of Heidelberg). He and his group established a database for the clinical signs and symptoms as well as course and follow-up for radiation accident victims as a basis for the pathophysiological characterization and analysis of radiation, especially of the responses of the hemopoietic system, and also established a telecommunications linkage between the University of Ulm and the Ural Research Center for Radiation Medicine in Chelyabinsk, Russia, to support the clinical and hematological management of chronically radiation exposed inhabitants as a consequence of mismanagement of radioactive waste in the Techa River region.