The usefulness of recombinant human erythropoietin (rHuEPO) on autologous blood transfusion was investigated in 18 patients undergoing radical prostatectomy (mean age 67.4 years). A total of 800 ml blood was deposited by two donations of 400 ml each, concomitant with subcutaneous administration of 24,000 U rHuEPO at each donation. All patients completed two successive donations with no adverse effects. The mean hemoglobin concentration was 13.7 g/dl before the donation and 13.0 g/dl on the day of operation. The decrease in hemoglobin was effectively prevented in 12 patients (66.7%) with rHuEPO, when compared with the predicted decrease in the absence of recovery from anemia. During radical prostatectomy, no homologous blood transfusion was required in 16 of 18 patients (88.9%). In conclusion, predeposit autologous blood transfusion with rHuEPO is useful for diminishing the risks associated with homologous blood transfusions.