The use of recombinant human erythropoietin (rhEPO) has greatly facilitated the treatment of anemia in children with chronic renal failure, but is expensive. Several reports on adult patients have shown that supplementation with L-carnitine can decrease the requirement for rhEPO. The objective of this study was to investigate the effect of oral supplementation with L-carnitine on the rhEPO requirement in children on dialysis. We investigated 16 children on dialysis (11 hemodialysis, 5 peritoneal dialysis) with a median age of 10.2 years. All children were stable on rhEPO treatment at least 3 months before study entrance. After obtaining baseline data, all children were supplemented with L-carnitine 20 mg/kg/day. Data were collected for 26 weeks. Follow-up was completed for 12 patients (8 hemodialysis, 4 peritoneal dialysis). At baseline free carnitine (32+/-18 micromol/l) and total carnitine levels (54+/-37 micromol/l) were normal. At the end of the study free carnitine levels had increased to 97+/-56 micromol/l (P<0.05) and total carnitine levels to 163+/-90 micromol/l (P<0.05). There was no significant change in rhEPO requirement. Hemoglobin level or hematocrit did not change significantly during the study. In conclusion we could not demonstrate a beneficial effect of supplementation with L-carnitine on rhEPO requirement in children on dialysis.