Hemodiafiltration (HDF) can augment the efficiency of removal of small and large solutes for renal replacement therapy. Double high-flux HDF was developed in 1984 with the objective to shorten treatment time compared to conventional therapy. It consists of a serial pair of dialyzers in the extracorporeal circuit for optimal diffusion and filtration, with substitution by backfiltration of bicarbonate dialysate under volumetric control. Used in conjunction with high blood and dialysate fl ow rates and high-flux membranes, unmatched high rates of simultaneous diffusive and convective solute transport can be obtained clinically with double HDF. A favorable long-term clinical outcome in comparison with conventional hemodialysis was observed with this therapy, despite shorter treatment times.