Recombinant human erythropoietin (epoetin) is widely used for correction of anaemia in patients with chronic renal disease and its efficacy has been confirmed in numerous studies. Disturbances in carnitine metabolism may also contribute to the development of renal anaemia. Although increases in erythrocyte count (RBC) and changes in RBC metabolism during L-carnitine administration have been observed, supplementation with L-carnitine in anaemic hemodialysis patients is not routine. The aim of our study was to determine the influence of epoetin on hematological parameters and plasma carnitine profile in anaemic hemodialysis patients. 36 hemodialysis patients (22 men, 14 female, aged from 17 to 64 years, mean 43) and 30 healthy volunteers (12 men, 18 female, aged from 25 to 65 years, mean 40) were studied. Epoetin (Eprex, Janssen-Cilag) was administered subcutaneously for twelve months with the starting dose 2000 IU three times per week (range from 75 to 133, mean 102 +/- 21 IU/kg/week). The target hemoglobin (Hb) range at the time of the study was between 10-11 g/dL. Laboratory markers of hematological response, carnitine and iron status, were measured before epoetin administration and then controlled every three months. During epoetin treatment a significant increase in Hb concentration was observed (100% of patients responded to epoetin). In the third and six month of epoetin treatment, along with a significant increase in mean reticulocyte count and the highest increment of RBC count and Hb levels, probably due to increased erythropoiesis, a significant, transient decrease of mean total and free plasma carnitine levels was observed. This may suggest the utilisation of carnitine by a new RBC population. It also indicates that there is a need for L-carnitine in carnitine deficient maintenance hemodialysis patients particularily during erythropoiesis induced by epoetin treatment.