The effect of renal transplantation on left ventricular function was evaluated in 14 patients with end-stage renal disease requiring maintenance hemodialysis. They had no apparent clinical evidence of heart disease. Ischemic heart disease was excluded by history, electrocardiography and radionuclide ventriculography. Echocardiography and radionuclide ventriculography were recorded in the interdialytic periods. Sixty-four per cent of the patients had abnormal left ventricular function despite adequate hemodialysis. Left ventricular function was reassessed within the first two months after successful renal transplantation. All parameters improved shortly after the transplantation. Cardiac index increased by an average of 0.76 +/- 0.11/min/m2 (P less than 0.001), stroke volume by 23.9 +/- 0.5 ml (P less than 0.001), ejection fraction by 9.7 +/- 1.9% (P less than 0.001), mean normalized posterior wall velocity by 0.17 +/- 0.06 second-1 (P less than 0.01), mean velocity of circumferential fiber shortening by 0.28 +/- 0.02 circle/second (P less than 0.001), and mitral valve diastolic closure rate by 17.2 +/- 2.3 mm/second (P less than 0.01). Our findings support the existence of a specific uremic cardiomyopathy which is a functional defect probably related to poorly dialyzed uremic toxins.