Aim. To evaluate changes in hereditary burden of sick sinus syndrome (SSS) in families of patients with SSS and assess heart rate variability (HRV) in patients with SSS.Results. 33 families of patients with SSS were examined. Clinical study, ECG-Holter monitoring, atropine test, transesophageal left atrial stimulation, echocardiography, veloergometry were fulfilled in all probands and their relatives in 1990 and 2005-2006. Cardiorhythmography was done in patients with SSS only in 2005-2006.Results. Increase in hereditary burden with SSS from 31 to 35% is registered during 15 years. Significant growth of patients with SSS was observed among daughters (from 50 to 71%), nephews (from 33 to 50%) and nieces (from 0 to 20%). HRV analysis shows prevalence of sympathetic system activity in patients with SSS.Conclusion. Growth of hereditary burden with SSS especially among female relatives is shown. HRV analysis can be used for SSS diagnostics.