[en] The results obtained from the canine experiments learly show that in the case of whole body irradiation in the dose range of 0.4 Gy, if given acutely, and in the dose range of 0.6 Gy if given in fractions or chronically, CFC-GM changes in the blood can be shown that are indicative of damage to the bone marrow CFC-GM compartment. However, in contrast to the in vitro situation no exact dose response relationship can be defined due to the large inter- and intra-individual variations in the blood CFC-GM concentration. The data obtained from the follow-up studies, on the other hand, point to a very important aspect, namely that on the basis of blood CFC-GM alterations some residual damage to the bone marrow can be demonstrated even 160 days after a radiation dose of approx. 0.8 Gy. From the results obtained from patients in the course of radiotherapy, though quite limited, it becomes evident that the method of blood CFC-GM determinations as an assay of bone marrow function after irradiation in principle is transferable to man. However, up to now it is quite unclear in which way the pattern of blood CFC-GM alterations will differ for different exposure conditions. (orig.)