Erythropoietin was used in 10 patients undergoing elective cardiovascular operations who were compromised with anemia. Initially, their blood hemoglobin levels were less than 10 g/dL (range, 7.5 to 9.9 g/dL). Erythropoietin (600 to 700 units/kg per week) was administered intravenously or subcutaneously for about 2 to 12 weeks. Blood hemoglobin levels increased in each patient (11.0 to 14.5 g/dL) until the day operation, and during this course autologous blood donations (400 to 1,200 mL) were obtained from 8 patients. As a result, homologous blood transfusions were needed in only 1 patient in whom erythropoietin treatment was interrupted for other reasons. All these patients were discharged without event, and no adverse effects due to erythropoietin were found. Although the causes of anemia were not specified in some of these patients, it was noteworthy that erythropoietin was effective even in a patient with hypoplastic bone marrow. Subcutaneous use was assumed to be especially favorable in managing anemic patients, in whom preoperative erythropoietin treatment could be continued for up to 82 days. We conclude that erythropoietin would be beneficial for the anemic population to secure homologous-blood-free operations.