Cardiomegaly and impaired myocardial function are frequent in patients on maintenance hemodialysis. One important reason is probably severe renal anemia. Substitution with recombinant human erythropoietin (rhEPO) results in long-term correction of renal anemia. We investigated the changes in cardiac function under rhEPO therapy using echocardiography. 13 patients with severe renal anemia (hct less than 26%) but independent of regular blood transfusions during the last six months were treated with 40-120 IU/kg rhEPO intravenously three times/week. Echocardiographic studies were performed in the anemic state and when hematocrit values were stable at levels above 30%. Left ventricular end-diastolic diameter (LVEDD) and end-systolic diameter (LVESD) were reduced (LVEDD: 53.9 +/- 4.2 mm vs. 51.4 +/- 5.8 mm; LVESD: 35.7 +/- 5 mm vs. 32.8 +/- 5 mm). Mean end-diastolic volume (LVEDV) and end-systolic volume (LVESV) were also diminished (LVEDV: 141.9 +/- 25.4 ml vs. 128.1 +/- 32.5 ml; LVESV: 54.8 +/- 18.6 ml vs. 45.1 +/- 17 ml). Stroke volume (SV) fell slightly from 87.1 ml to 83 ml resulting in a decrease of cardiac output (CO) from 6.9 +/- 1.6 l/min to 6.2 +/- 1.7 l/min. The thickness of the left ventricular posterior wall (LVPW) and of the septum interventriculare (IVS) remained constant. Myocardial contractility indicated by ejection fraction (EF), fractional shortening (FS) and the velocity of circumferential fiber shortening (VCF) frequently improved. Our data indicate that correction of renal anemia by rhEPO can improve myocardial function in patients on maintenance hemodialysis.