Current methods of renal replacement therapy lead only to an insignificant removal of larger, potentially toxic, substances, which are excreted by healthy kidneys. On-line preparation of substitute from dialysate and the use of high-flux membranes allow substantial convective removal of such substances. Comparing conventional haemodialysis to on-line haemodiafiltration regarding the control of anemia and the dosage of erythropoietin and iron therapy in patients with end stage renal disease on regular hemodialysis. This study included 16 pediatric patients below 16 years of age with end stage renal disease on maintenance hemodialysis 3times/week, 4 hours per session, at the Centre of Pediatric Nephrology and Transplantation, Cairo University. Initial hemoglobin, hematocrit and iron indices (iron, total iron binding capacity and ferritin) were done before initiation of hemodiafiltration. Follow up red blood cell and iron indices (hemoglobin, hematocrit, iron, total iron binding capacity and ferritin ) were done 3 months after initiation of hemodiafiltration. The results of this study showed that the on-line HDF is superior in control of anemia than the conventional HD.