Preoperative autologous blood donation is widely used in cardiac surgery. However, some patients are unable to store adequate amounts of blood before surgery, and some develop anemia after the operation. We attempted to clarify the limitations of blood donation alone and its influence on erythropoiesis in comparison with those associated with adding recombinant human erythropoietin (rEPO). Subjects were twenty-five patients who were scheduled to undergo elective cardiac surgery. A unit of autologous blood (200 ml) was to be donated every 3 or 4 days for 2 weeks. 200mg of ferrous sulfate was given orally every day in 10 patients (the simple donation group), while 200 U/kg of rEPO was given intravenously 3 times a week in combination with oral ferrous sulfate supplementation in 15 patients (the rEPO-treatment group). After donation, reticulocyte counts increased significantly in both groups. In the simple donation group, hematocrit levels decreased significantly (p < 0.02), while serum iron levels did not change significantly. In the rEPO-treatment group, hematocrit levels remained unchanged and serum ferritin levels decreased significantly (p < 0.02) after the donation; in addition, serum iron levels in the rEPO-treatment group decreased significantly (p < 0.05) than those in the simple donation group during donation. The erythroid/nucleated cell ratio remained almost normal in the simple donation group. This ratio was significantly higher in the rEPO-treatment group than in the simple donation group (36.4 +/- 8.3% versus 26.2 +/- 6.8%, p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)