Atrial fibrillation (FA) is the most common arrhythmia, and frequency of its occurrence increases with age. The aim of this study was to assess the influence of sinus rhythm (SR) restoration on heart rate (HR) and ventricular arrhythmia (AEV) and pauses (PA) occurrence in patients in over 70 years age. Study group consists with 104 patients with nonrheumatic FA of different etiology, which were divided to two groups: in younger and older age. In group I (younger patients) were 52 patients (25 women and 27 men), 38 to 69 (mean 51.2 +/- 14.2) years old. In group II (older patients) were 52 patients (23 women and 29 men), 70 to 86, (mean 71.3 +/- 5.5) years old. In all patients Holter monitoring before reversion of atrial fibrillation was performed. Consequently sinus rhythm (SR) was restored using pharmacological or electrical cardioversion. After SR stabilization next Holter monitoring was performed. The following electrocardiographic parameters was assessed: mean heart rate (HR mean), maximal heart rate (HR max), minimal heart rate (HR min), occurrence of AEV and PA over 2000 ms duration time. The PA over 2000 ms duration time occurred significantly more often during FA than after SR restoration. HR max was significantly higher during FA compared to during SR. Similar changes in HR mean was noted. HR min was nearly constant both in FA and SR. The frequency of AEV occurrence was different according to Lown class. In clinically benign arrhythmia (class I and II) similar occurrence of ventricular ectopic beat either during FA and SR was observed. However ventricular arrhythmia Lown's class III and IV was observed more frequently during FA than after SR restoration. Ventricular arrhythmia Lown's class V only in one older patient during FA was recorded, and after reversion to SR wasn't observed. Reversion of FA to SR allows to better control HR and may prevent to arise or increase heart failure in the elderly. Number of PA during SR is considerably smaller compared to FA, which reduce risk of central nervous system ischemia in the elderly.