The preoperative donation of autologous blood is a procedure with a substantial, albeit not yet quantifiable risk for the patient. The risks of homologous transfusion, which shall be avoided by autologous blood, have been permanently decreasing during the past several years Thus, if preoperative autologous blood donation is performed at all, it has to be performed in an optimal way to improve the overall transfusion risk for an individual patient considering the very low risks nowadays associated with homologous blood transfusion. The compensatory erythropoiesis after repeated autologous blood donation shows marked interindividual variability. Patients with a weak erythropoietic response have an elevated risk to need homologous blood. It is a main focus of this work group to explore the mechanims underlying this variability and to investigate measures to enhance the power of compensatory erythropoiesis after autologous blood donation.