Ten patients with end-stage renal failure and anaemia (mean haemoglobin 6.1 g/dl, range 4.6-8.8 g/dl) on thrice-weekly haemodialysis were treated with human erythropoietin derived from recombinant DNA (rHuEPO). This was given as an intravenous bolus after each dialysis in rising doses within the range 3-192 IU/kg. All patients showed increases in reticulocyte numbers and haemoglobin concentration and after the first week of treatment none of the four previously transfusion-dependent patients needed further transfusions. In nine patients treated for 12 weeks haemoglobin rose to a mean of 10.3 g/dl, range 9.5 to 12.8 g/dl. Thereafter the dose of erythropoietin was adjusted to avoid a further rise in haemoglobin. During treatment one patient had an episode of hypertensive encephalopathy and two had clotting in their arteriovenous fistulas (complete in one). rHuEPO is an effective treatment for the anaemia of end-stage renal failure but longer-term observations are needed on the consequences of increasing the haematocrit.