Eighteen patients on chronic hemodialysis with renal anemia were treated with recombinant human erythropoietin (r-HuEPO). Hemodynamic parameters in the resting state were determined before and after successful treatment. Posttreatment cardiac index was decreased (3.3 v 2.8 L/min/m2), whereas diastolic blood pressure (72 v 79 mm Hg) and calculated peripheral resistance (2,230 v 2,860 dyne.cm.s-5) were increased significantly when compared with the pretreatment period. We conclude from our study that the increase of blood pressure as seen in patients on dialysis, who are effectively treated with r-HuEPO, is due to an increase in peripheral resistance. This increase overrules the decrease of cardiac index and might well be a result of peripheral vasoconstriction due to improved oxygen availability.