The efficiency of hemodialysis can be more than doubled. This involves deviating from conventional blood and dialysate flows, employing dialyzers with greater surface area and permeability, bicarbonate dialysate, and an apparatus capable of rigid volumetric control of the dialysate. Coupled with the better treatment tolerance described elsewhere in this volume, this self-contained and automated technique providing high diffusive and convective transfer permits drastic reductions in treatment time over conventional dialysis: in our study, to under 6 hrs/wk.