14 patients with advanced uremia had a mean cardiac index (CI) of 4.37 +/- 0.25 liters/min/m2, a mean stroke work index (SWI) of 65.6 +/- 3.7 g/m/m2 and a mean left ventricular filling pressure (LVFP) of 16.3 +/- 2.1 mm Hg. The left ventricular performance was estimated to be normal when CI or SWI changes were correlated with simultaneous variation of the LVFP attained during peritoneal dialysis or afterload reduction. CI was high at a normal LVFP, it decreased at low or high LVFP. Guanidines retention, metabolic acidosis and hypocalcemia did not prevent the maintenance of a high CI or SWI. Out of 32 patients, left ventricular hypertrophy and pericardial effusion, conditions which may affect ventricular distensibility, were present in 25 and in 22 echocardiograms, respectively. We suggest that in uremic subjects, LVFP is primarily influenced by volume loads and by ventricular distensibility modifications.