The site where the clinical trial will be conducted is at the St-Luc hospital from the CHUM. This is a prospective randomized study that will compare the two treatment modalities, HD and HDF, through economics and pharmaco-economics parameters.

Patients, who had previously been randomized in the CONTRAST study, will remain in their respective group and monitoring will continue. The next patients will be randomized in the same way (1: 1) using the same inclusion and exclusion criteria. HDF randomized patients will receive post-dilution standard reinjection (at least 100ml/min or 6 liter/hr). In rare cases, HDF patients can briefly have reinjection on a pre-dilution mode (if heparin need to be avoided for example) and the reinjection flow should be adjusted accordingly (200ml/min).

Length and frequency of sessions will be the same in the 2 groups. Blood tests will not change and will be the same than those used as routine assessments. Metabolic control of patients will be maintained according to the guidelines. Patients will be monitored for a minimum of 3 years. A set of demographic and clinical data will be collected from patient medical records and throughout the study.

Biochemical data as part of the usual blood tests of dialysis patients will be collected each month as well as will be stored and analyzed information about the annual cardiac ultrasounds.

All events will be scored (hospitalizations, patterns, duration) and the list and cost of drugs will be compiled every three months. These data will be useful in the economic analysis comparing the two treatment modalities.

Inclusion Criteria:

• more than 18 years old,
• able to consent,
• patient needs to be on hemodialysis more than 8-12 hours a week (2-3 sessions)

Exclusion Criteria:

• severe none compliance (often missing sessions without good reasons),
• life expectation less than 3 months,
• treated with high-flux filters in the last 6 months