Introduction. It is known that cardiovascular diseases, including cardiac arrhythmias, are accompanied by increased activation of the sympathetic-adrenal system (SAS). Hyperactivation of the SAS causes an increase in the level of circulating catecholamines - adrenaline and norepinephrine, resulting in desensitization of β-adrenergic receptors (β-AR), aggravation of myocardial contractile dysfunction and the development of arrhythmia. Indicators of SAS tension are β-adrenergic reactivity of erythrocyte membranes (β-ARM) and the level of circulating catecholamines. One of the most common arrhythmias is atrial fibrillation (AF), which leads to a decrease in the quality of life, disability and high mortality. Therefore, among patients with AF, it is important to study the functional viability of β-AR in different periods of the disease. Purpose: to evaluate β-ARM and the level of adrenaline, norepinephrine in patients with AF before and after surgical treatment. Materials and methods. The sample included 47 patients - 31 men and 16 women, the age in the sample was 51 (26; 77) years. All patients were diagnosed with AF based on ECG and 24-hour monitoring. Among the entire sample, 59.6% of patients had paroxysmal, 25.5% persistent, 14.9% long-term persistent forms of AF. All patients underwent surgical treatment of AF using radiofrequency or cryoablation. β-ARM was determined by the method of assessing changes in erythrocyte osmotic resistance as a result of blockade of β-AR in vitro with a selective β-adrenergic blocker (Β-ARM, AGAT, Russia). Plasma epinephrine and norepinephrine concentrations were determined by enzyme-linked immunosorbent assay using Adrenalin ELISA and Noradrenalin ELISA kits (Tecan IBL International, Germany). The parameters were studied in all patients before treatment, in 44 patients after 3 days, in 18 patients after 3 months and in 9 patients after 12 months after ablation. The significance of changes in β-ARM and catecholamine levels before and after ablation was assessed using the Wilcoxon test. The strength of the linear relationship between quantitative indicators was assessed using the Spearman rank correlation coefficient. Results. In the study sample, there were no statistically significant changes in β-ARM and adrenaline levels before and at different times after ablation. Thus, the level of β-ARM before surgery was 18.2 (12.6; 25.4), after 3 days - 22.3 (14.4; 26.6), after 3 months - 20.3 (9.3 ; 29.3), and 12 months after the operation - 27.7 (16.8; 36.7). The level of adrenaline before surgery, 3 days, 3 months and 12 months after surgery was 4.4 (3.7; 6.9), 4.7 (3.0; 6.4), 4.6 (2 .5; 6.6), 5.6 (9.1; 8.8). However, an increase in the level of norepinephrine was found 12 months after ablation compared with the values before treatment and 3 days after treatment by 1.7 and 1.8 times, respectively (p = 0.028). The level of norepinephrine before surgery, 3 days, 3 months and 12 months after surgery was 40.9 (18.7; 56.6), 38.6 (14.8; 49.6), 46.7 (25 .6; 57.3), 69.3 (65.1; 80.1). Before surgery, β-ARM and norepinephrine levels were linearly correlated (r = 0.335, p = 0.037), but after treatment, the linear correlation disappeared. At 3 and 12 months after ablation, there was a strong linear correlation between adrenaline and norepinephrine levels (r = 0.611, p = 0.012; r = 0.786, p = 0.036, respectively). Conclusion. In the sample of patients with AF, β-ARM and norepinephrine levels were linearly correlated before treatment, but after ablation, the correlation disappeared. At the same time, the values of β-ARM do not change statistically significantly, and the level of norepinephrine increases during a 12-month follow-up. Thus, 12 months after treatment in patients with AF, the activity of the CAS increases, but the functional viability of beta-AR does not change significantly.