<qa>  What is the primary end point of HDF?Therefore, we propose a prospective, randomized multicenter trial, comparing on-line HDF with HD. After a stabilization period, an expected number of 700 chronic HD patients will be randomized to either HDF or low-flux HD and followed during 1-6 years. Primary end points are all cause mortality and combined CV events and mortality. In addition, LVMi, PWV, CIMT and various parameters of oxidative stress, acute phase reaction APR and endothelial function will be assessed and compared between treatment groups. 