The purpose of the study is to compare clearance and removal rates of phosphate, ß2-microglobulin (ß2-m) and leptin and albumin loss with different dialyser membranes during post-dilution online hemodiafiltration.

Inclusion Criteria:

• hemodialysis patients 18 years and older
• treated by post dilution on-line Hemodiafiltration (HDF) for at least one month
• who reached a dialysis dose (Kt/V) of at least 1.2 at each of the last two monthly checks
• who are on a stable anticoagulation and anemia management
• whose hemoglobin is between 10.5 and 13.0 g/dl
• who are clinically stable based on judgment of nephrologist
• who are on a regular thrice weekly HDF schedule, e.g. Monday-Wednesday-Friday or Tuesday-Thursday-Saturday,
• who have a good vascular access (fistula or graft) which enables easy insertion of the needles and suitable effective blood flow (> 300 ml/min)
• who are able to understand the nature and requirements of the clinical investigation and who have given written informed consent

Exclusion Criteria: Patients

• with active Hepatitis B, Hepatitis C or HIV infection
• who are severely malnourished as judged by the principal investigator
• who are known or suspected to have allergy to the trial products or related products
• with a central venous catheter based vascular access
• who are abusing non-legal drugs or alcohol
• who have currently active malignant disease
• who are female of child-bearing age without effective measures of contraception, pregnant or breastfeeding
• who participate simultaneously in another clinical investigation
• who have participated in othe clinical investigations during the last month
• who are uncooperative