Some studies have demonstrated circadian incidence of sudden cardiac death (SCD), ventricular ectopies, acute coronary syndromes and heart rate variability. One of new parameters applied in non-invasive stratification of sudden cardiac death is heart rate turbulence (HRT). Detection of circadian oscillations in HRT and optimised measurement of HRT can increase the positive predictive value of HRT as a sign of SCD risk. The set consisted of 48 patients in a sequence order aged 45 +/- 12 years (of which 23 men and 25 women), indicated for Holter monitoring ofventricular ectopies who had good left ventricular function with LV EF 0.53 +/- 0.11. HRT was measured in two-hour intervals within a 24 hour period, followed by an analysis of circadian dependence of HRT. A significant circadian oscillation in the TS (turbulence slope) parameter was recorded. No circadian signs were detected for the TO (turbulence onset) parameter. The project is supported by grant no. NR/8478-3.