The purpose of this study was to investigate whether chronic subcutaneous administration of epoetin has an influence on its pharmacokinetics in patients with chronic renal failure and anaemia. 14 Patients were included in the study. The data of 8 patients could be evaluated at the end of the study. All patients were on maintenance haemodialysis. The pharmacokinetic profile of epoetin was studied directly after the first subcutaneous administration of 60 U/kg body weight. Patients were further treated with epoetin to maintain haemoglobin concentration between 6.0 and 6.5 mmol/l. After about one year of treatment the pharmacokinetic profile was studied again, using the same dosage. Between both profiles no significant differences (paired Student's t-test) were found in the pharmacokinetic parameters studied: absorption half-life, time to maximum concentration, maximum concentration, elimination half-life, area under the curve and mean residence time. However, in individual patients large differences may be found.