We performed retrospective analysis of 135 case histories of patients with first episode of non-valvular atrial flutter (AF): 116 (85.9 %) men and 19 (14.1 %) women aged 55.7±1.0 years. Over 15 years of follow-up permanent atrial fibrillation or flutter was registered in 85.8 % of patients, rare paroxysms – in 10.2 % patients, frequent paroxysms (at least once per 3 months) – in 2.4 %, no arrhythmias – in 1.6 %. The maximum frequency of the permanent AF was registered in the first 10 years. No antiarrhythmic drug therapy was needed in 83.3 % patients with sinus rhythm preserved over 15-year period. Prognosis of AF and the effectiveness of catheter treatment is defined by the presence of concomitant atrial fibrillation.