 To predict appropriate replacement rates, Hospal Gambro scientific laboratories have developed a calculation model to predict the physiological interactions between the components of the administered replacement- and hemodialysis fluids and the patients complex metabolic system. These interactions are influenced, in large part, by systemic parameters such as blood-flow and ultrafiltration rates, and patient parameters, such as acid base-status and liver function. This calculation model needs clinical validation in respect to its ability to predict the outcome and narrow the margin of metabolic disturbances caused by the administration of citrate anticoagulation. A previous study of a similar replacement fluid using citrate 8 mmolL and citric acid 4 mmolL resulted in mild metabolic acidosis of minimal clinical significance in some subjects and so this study will evaluate a modified version of fluid containing citrate 10 mmolL and citric acid 2 mmolL which has been calculated to provide optimal metabolic balance. 