A theoretical comparison of various treatment strategies for the dialysis of patients with chronic renal failure has been made covering a wide mol wt spectrum (60 to 5250 daltons) of metabolites. A two-compartment model has been used with the generation rate in the appropriate pool. The comparison for any given metabolite is made, keeping the same level of predicted intracellular concentration as in traditional Kiil treatments, and it is found that the number of treatment hours per week may be reduced pro rata as the dialyzer clearance is increased. This result is independent of the assumed site of metabolite generation, of the distribution volumes, and of the level of the cell wall permeability. The cyclic fluctuation in intracellular concentration and the mean level of intracellular concentration, in relation to the level in normal health, are both predicted for a given metabolite to be lower if thecell wall permeability is assumed to be on the low side rather than on the high side. The clinical implications of the variations in intracellular and extracellular concentration are discussed, and considerable elevation compared to normal health is predicted for both compartments for large molecules, larger than or equal to 1,000 mol wt, which are generated effectively in the extracellular compartment.