43 patients with end-stage renal failure maintained on hemodialysis were studied by echocardiography before and after hemodialysis. Considering possibility, that left ventricule can be enlarged due to intrinsic factors impairing their performance, like myocardial fibres damage in coronary disease or inflammation and extrinsic factors like hypertension, overhydration, anemia, arteriovenous shunt and humoral changes (electrolyte imbalance, uremic toxins, acidosis) three groups of patients were chosen: A--with normal left ventricular diameter, B--with enlarged left ventricule before and after dialysis, C--with enlarged left ventricule only before dialysis. Mean velocity of circumferential fibre shortening (mVcf) and ejection fraction (EF) as left ventricular contractility indexes and end-systolic meridional wall stress as afterload index were determined. Stress-shortening relations before and after hemodialysis were compared in groups, to determine possible intrinsic contractility impairment of the left ventricule. No differences in groups were found in preload reduction (weight loss) and humoral changes (BUN, creatinine, pH, potassium, calcium, hematocrit), also blood pressure was not significantly different in all groups. Hemodialysis improved contractility only in patients with normal left ventricular diameter and significant reduction of afterload. In group A and C stress-shortening relation increased after dialysis. In group B decreased probably because of the lack of mVcf improvement despite reduction of stress in two patients. It is possible that these two patients had impaired contractility and enlarged left ventricle due to intrinsic factors.