This noninvasive echocardiographic study of cardiac performance in 27 patients with chronic renal failure and vascular access documented the magnitude of forward cardiac output to be 65 per cent of the observed index. Hemodialysis resulted in acute hemodynamic changes, including an average fall in the cardiac index of 57 per cent, presumably because of a 40 per cent decrease in left ventricular filling volume. In patients in whom the vascular access had functioned longest, a time related cardiac decompensation is suggested by a cardiac index of significantly less than normal, p, 0.0013, with occlusion. Ventricular function was suboptimal three months post-transplant, as reflected by a continued low cardiac index and depressed ejection fraction, although the general reduction in cardiac index and diastolic volume on postoperative day 7 was of the magnitude expected from arteriovenous access occlusion.