The purpose of our research was to study indices of heart rate variability at patients with paroxysmal and persistent forms of atrial fibrillation/flutter. 133 patients (mean age 53.8 ± 0.9 years) have been included into research: 113 patients with paroxysmal (28 %) and persistent (72 %) forms of atrial fibrillation/flutter with various cardiac diseases, but without significant structural changes of a myocardium. Twenty patients were included into thef control group (rather healthy young men without presence any cardiac pathology and atrial fibrillation). In patients with atrial fibrillation/atrial flutter considerable deterioration of autonomic nervous system status mas observed. The estimation of indicators heart rate variability may be used for prediction of atrial fibrillation/flutter course: prevalence of paroxysms, their character and probability of the permanent form development.