All patients in the first group tolerated sampling of four transfusion units of autologous blood in the course of two weeks with subsequent erythropoietin administration very well. Erythropoietin was well tolerated, no local nor systemic undesirable side-effects or complications were observed. The mean transferrin and serum iron values remained during sampling of autotransfusions and erythropoietin administration within the range of normal values reported by our laboratory. The ferritin levels were above the norm. On the other hand in patients of the control group it was not possible--due to the decline of haemogram values--to sample in 45% the required amount of autologous blood before operation. For the same reason it was not possible to implement haemodilution as required. In similar blood losses administration of allogenic blood was necessary in 35% patients of the control group whereby in the group of patients with erythropoietin allogenic blood was administered in two cases (10%). Erythropoietin administration can effectively facilitate preoperative sampling of autotransfusion within a relatively short period. By its administration we can prevent a marked decline of red blood cells as a result of sampling of several preserves of autologous blood at a rapid rate. A satisfactory value of the haematocrit before the operation proper moreover makes it possible to collect a larger amount of blood in case of acute isovolaemic haemodilution. This enhances the patient's safety in relation to risks ensuing from administration of allogenic blood.