We evaluated endogenous serum erythropoietin (Epo) levels in 14 normal subjects (eight males and six females) after a single 400-ml phlebotomy. The subjects were followed up for 56 days. The hemoglobin (Hb) values of both males and females decreased to a nadir on days 3 to 7 post-phlebotomy. Hb values gradually increased, but did not completely recover to pre-phlebotomy levels by day 56. Serum Epo levels increased after 6 h post-phlebotomy, to 20.1 +/- 5.4 (mU/ml) in males and 20.7 +/- 7.0 in females, from the pre-phlebotomy levels of 14.6 +/- 4.0 in males and 13.4 +/- 4.1 in females, respectively. Epo levels continued to increase to peak levels of 25.5 +/- 6.3 in males and 28.7 +/- 11.5 in females on days 7 to 14 and thereafter decreased until day 56. Thus, the Epo response to a 400-ml phlebotomy was relatively small in magnitude and was not sufficient to initiate a significant increase in erythropoiesis. This finding suggests that the administration of recombinant human erythropoietin (rHu-Epo) may be effective for the prompt correction of anemia induced by autologous blood donation and for increasing the volume of predonated autologous blood.