BACKGROUND Anaemia of chronic renal failure is primarily due to relative erythropoietin deficiency. This hormone has been recently cloned and it is now available for clinical use. METHODS Sixteen patients maintained on haemodialysis with non-complicated anaemia and on stable clinical condition were selected for 12 months' treatment with r-HuEPO. Our aim was to analyse the factors influencing r-HuEPO response and the modifications on main haematological and biochemical parameters and adverse reactions occurrence. RESULTS All patients responded with an increase of haemoglobin (from 78 +/- 9 to 103 +/- 18 g/dl at second month of therapy, p less than 0.001) and blood transfusions were eliminated. Time of response and doses were very different to one another. R-HuEPO requirements decreased slowly with time. Neither transfusion number, nor hyperparathyroidism, nor ferritin levels, nor diabetic condition influenced r-HuEPO response. Serum ferritin decreased significantly from 1,772 +/- 1,791 to 1,116 +/- 1,240 ng/ml (p less than 0.05), especially in patients without iron overload. Serum vitamin B12 levels did not decrease significantly. Both uric acid and phosporus increased significantly after the treatment period (5.25 +/- 1.18 to 6.29 +/- 0.99 mg/dl and 5.78 +/- 1.29 to 6.69 +/- 1.55 mg/dl respectively, p less than 0.01). Platelet counts did not modify. It was necessary to adjust antihypertensive therapy in a few patients because of a mild rise in blood pressure, although important adverse reactions did not occur. CONCLUSIONS Anaemia of haemodialysis patients improves with r-HuEPO treatment and reduces blood transfusion requirement. Adverse effects are not very remarkable.