The effects of recombinant human erythropoietin (rHuEPO) on improving the anemia associated with autologous blood collection before open heart operations and on improving the postoperative anemia were studied. The study was carried out on 18 patients undergoing coronary artery bypass operations; 400 mL of autologous whole blood was taken from each patient 2 weeks before operation and was subsequently used in the operation, and rHuEPO (100 U.kg-1.day-1) was given intravenously for 2 weeks before operation and for 1 week after operation. The group in which iron preparations were also administered intravenously was designated as group I (10 patients), and the group in which rHuEPO was given alone was designated as group II (8 patients). In group III, as a control group, 11 past patients were used in whom 400 mL of autologous whole blood was collected 2 weeks before operation but neither rHuEPO nor iron preparations were given. After autologous blood collections, the hemoglobin levels improved in group I, group II, and group III, in that order, and with significant differences among them. It was shown that rHuEPO was effective in ameliorating the anemia associated with preoperative autologous blood collection, and the effect was further enhanced with intravenous supplementing iron preparations. After operation, the anemia markedly improved while rHuEPO was administered, but the hemoglobin levels decreased rapidly when the administration was terminated. Further studies are needed regarding the use of rHuEPO after operation.