Left ventricular function was investigated in 21 chronic hemodialysis patients with cardiomegaly not due to major pericardial effusion. Angiographic and hemodynamic studies were performed in all, and selective coronary angiography in 16 patients. 5 patients had a history of long-standing arterial hypertension, 5 had clinical evidence of coronary artery disease, 3 had an overfunctioning arteriovenous fistula, and 3 had valvular heart disease. In 10 patients progressive cardiac failure developed without any apparent cause. The diagnosis of congestive cardiomyopathy was established in the latter by left ventricular catheterization. Their myocardial dysfunction was characterized by a significant increase in left ventricular end-diastolic volume when compared to control values. The mean myocardial contractility indices were significantly decreased, as was the index of normalized ventricular rigidity. Of the 10 patients, 6 presented the complete picture of the disease. The remaining 4 also had marked left ventricular dilatation and a decreased normalized rigidity index but their ejection fractions were in the normal range and their myocardial contractility indices only moderately decreased. 7 had coronarography, their coronary arteries were found normal. Of the 5 patients with angina, 3 had significant coronary artery disease as demonstrated by coronary angiography but 2 had angiographic and hemodynamic findings compatible with congestive cardiomyopathy and hypertrophic cardiomyopathy, respectively, in the absence of coronary heart disease. Among the remaining 6 patients with variable underlying etiologies 3 had myocardial dysfunction also compatible with congestive cardiomyopathy while 3 others had left ventricular function near normal. The severe ventricular dysfunction of one of them was possibly related with both aortic and mitral insufficiency. 5 of them had coronary angiography. No significant coronary artery disease could be demonstrated in them. It is concluded that congestive cardiomyopathy in the absence of significant atherosclerotic coronary disease is an important feature of cardiac dysfunction in uremic patients with cardiomegaly undergoing intermittent hemodialysis.