With the improvement of hemodialysis, the coursc of thc discase in patient with endstage renal disease has been clearly improved. Nevertheless, among several shortcomings to our present mode of renal replacement therapy, cardiovascular complications have been the leading cause of morbidity and mortality. Several factors such as anemia, arteriovenous shunting of blood, intermittent extracorporeal circulation and hypartension may be contri-buting. But little is known about the quantitativc cardiac hemodynarnic charact"ristics occurred during hemodialysis. The purpose of this study is to observe the sequential hemodynamic changes before, during and after the hemodialysis and to investigat: reliable parameters in the detection of ventricular dysfunction. In the present study, equilibrium radionuclide cardia.c angiography was performed and left: and right ventricular volume indices, ejection phase indices of both ventricular, perfo-ramanc were rneasured in the 16 stable patients with chronic renal failure treated with maintenance hemodialysis sequentially i.e. beforc, during (carly and late phase) and after the hemodialysis. The results obtained were as follows; 1) The indices of the left ventricular function were not changed during the hemodialysis but increased after the hemodialysis. 2) The indices of the right ventricular function(EF, SVI) wcre significantly decreased in the early phase (15, 30 minutes after starting extracorporeal circulation) but recovered after the hemodialysis, 3) The ratio of right ventricular to left ventricular ejection fraction was significantly decreased in the early phase and the lung volume indices wcre significant1y increased at the same phase. As a conclusion, hemodiaiysis irnproves left vcntricular function maybe du to increased contractility, and effects on the right ventricular function maybc due to the increascd lung volume in the early phase of hemodialysis.