The main cause of mortality in patients on renal replacement therapy are disturbances in circulatory system including sudden death. Cardiac hypertrophy, ischemic heart disease, degenerative changes as a consequence of uremic cardiomyopathy and electrolyte disturbances constitute the main cause of cardiac arrhythmia. The differences in duration of QT interval in ECG leads are known as QT dispersion and may indicate on prevalence of cardiac arrhythmia leading to sudden cardiac death. In the paper we described prognostic significance of QT dispersion in patients on maintenance dialysis.