Study design: Open, randomized, cross-over, monocentric, controlled, prospective Applied Medical Devices: FX CorDiax 60 (high-flux), FX 60 (high-flux) Patients: 30 adult chronic hemodialysis patients Treatment: Each patient will be treated by post-dilution online hemodiafiltration once with each dialyzer type.

Study objectives: Intraindividual comparison of removal rate of urea, phosphate, ß2-microglobulin (ß2-m), myoglobin, prolactin, alpha1-microglobulin and alpha1-acidglycoprotein and of the albumin loss with different dialyzer membranes during post-dilution online hemodiafiltration.

Primary variable: Removal rate of myoglobin Secondary variable: Removal rate of urea, phosphate, ß2-microglobulin (ß2-m), prolactin, alpha1-microglobulin and alpha1-acidglycoprotein Safety variable: Hematocrit, albumin loss Sample Size: 30 subjects

Inclusion Criteria:

• Patients who are treated by post dilution on-line HDF for at least three months.
• Patients who reached a dialysis dose (Kt/V) of at least 1.2 at the last two monthly checks,
• Patients who are on a stable anticoagulation and anemia management,
• Patients who are clinically stable outlined by the medical history of the patient, based on judgment of principal investigator,
• Patients who are on a regular thrice weekly HDF schedule,
• Patients who have a good vascular access (fistula or graft) which enables easy insertion of the needles and suitable effective blood flow (> 300 ml/min),
• Patients who are able to understand the nature and requirements of the clinical investigation and have given written informed consent,
• Patients who are aged 18 years or older.

Exclusion Criteria:

• Patients who do not meet the inclusion criteria,
• Patients with active HBV, HCV, HIV infection,
• Patients who are severely malnourished patients as judged by the principal investigator,
• Patients who are known or suspected to have allergy to the trial products or related products,
• Patients who are abusing non-legal drugs or alcohol (defined as an average daily intake of more than one liter of beer per day or an equivalent amount of alcohol in other beverages),
• Patients who have been diagnosed a current active malignant disease,
• Patients who participate simultaneously in another clinical investigation or in other clinical investigations during the last month,
• Patients who are uncooperative.