A mathematical model of hemodialysis (artificial kidney treatment) that can accurately predict the changes in distribution of urea and creatinine in the patient's body during dialysis, for a wide range of system parameters. The model was validated using considerable clinical data from two patients, plus one-time data from 10 randomly chosen patients on the Kiil Dialyzer. The predicted fraction removed during dialysis was plotted as a function of blood-flow rate, length of dialysis, initial blood concentrations, and patient weight. Results suggest that in most dialysis patients, material removal during dialysis and blood concentrations afterward can be accurately predicted from just the patient's weight and his rate of blood flow into the dialyzer. The computer-generated results can be valuable to the clinician by showing the time needed to dialyze a given patient to achieve a desired result. 46 pp. Ref.