A two-compartment model of patient-artificial kidney system consisting of a cerebrospinal fluid (CSF) and a body liquor compartments have been presented. With the model, the mechanism of disequilibrium syndrome occurred in a patient undergoing hemodialysis has been discussed to simulate the CSF pressure transients. Urea, as an uretic toxin, was injected into dogs and in viva hemodialysis experiments have been performed under clinical conditions. The parameters in the solution, G and K, have been determined from experiments and are in good agreement with those reported under normal physiological conditions and in previous investigations.