Background/Aims: Inflammatory process induced by endotoxin is one of the causes of resistance to recombinant human erythropoietin (rHuEPO) in hemodialysis patients. Thus dialysate contaminated with endotoxin may diminish response to rHuEPO. We investigated whether dose of rHuEPO could be reduced with endotoxin-free ultrafiltered dialysate. Methods: Twenty-seven chronic hemodialysis patients receiving rHuEPO were studied. The patients did not have known causes of anemia other than chronic renal failure. An endotoxin-cut polyethylene ultrafilter was installed into the dialysate fluid circuit. Hematocrit and dose of rHuEPO were monitored before and after installation. Dose of rHuEPO was adjusted to keep hematocrit at about 30%. Endotoxin concentration of dialysate was measured by commercial limulus test (Endospecy<sup>®</sup>). Results: After installation of ultrafilter, dialysate endotoxin concentration decreased from >100 to <1.0 endotoxin units/liter (EU/l). Dose of rHuEPO decreased from 90.0 U/kg/week (median) to 57.3 U/kg/week (p < 0.05) and hematocrit increased from 30.3% (median) to 32.2% (p = 0.03) after 5 months of installation of ultrafilter. The running cost of the ultrafilter corresponded to only 4% of the cost of spared rHuEPO. Conclusions: Ultrafiltered endotoxin-free dialysate caused significant reduction in dose of rHuEPO to keep target hematocrit level. Endotoxin-cut ultrafilter was beneficial to hemodialysis patients in medical and in economical aspects.