In 14 stable ESRD patients an ABA cross-over study comparing conventional hemodialysis with post-dilution hemofiltration was performed in order to test the validity of clinical benefits reported for hemofiltration. No effect on blood-pressure could be observed in hypertensive hemofiltration patients when body weight was kept constant. The claimed positive effect of hemofiltration on hyperphosphatemia in dialysis patients could not be confirmed. A treatment with 3x18 I infusate per week seems to be insufficient treatment in regard to small molecule removal especially in heavy patients without any residual renal function. The decrease in urea nitrogen generation rate during the hemofiltration period might be the result of the lower small molecule removal in hemofiltration when compared to hemodialysis. The main clinical benefit of hemofiltration results from improved tolerance to volume removal due to improved hemodynamic stability during treatment.