The possibilities of anticoagulant therapy in patients with atrial fibrillation significantly increased during last years. The warfarin therapy can be ineffective in those patients who can't neatly follow regimen of treatment, to control international normalized ratio in blood or international normalized ratio is retained with difficulty on recommended level. The scale SAMe-TT2R2 is considered as appropriate one to apply for more exact preliminary evaluation of possibility of achieving anticoagulation under application of antagonists of vitamin K. The purpose of study was to validate scale SAMe-TT2R2 on the group of observed out-patients in a real clinical practice. The study included 55 patients receiving warfarin because of non-valvular atrial fibrillation. In 30 patients (54.5%) a paroxysmal atrial fibrillation was observed and in 25 patients (45.5%) – permanent form of this disease. The examined group included 14 females and 41 males with average age of 71,3 ± 7,52 years. The patients receiving warfarin were in target range of international normalized ratio (2–3) 64,3 ± 12,91%of intake time. The percentage of patients residing within target range of international normalized ratio 60% of time and more comprised 58.9%. In average, patients taking during a year warfarin as anticoagulant controlled international normalized ratio 9,6 ± 0,41 times. In the examined group, 30 patients had according scale SAMe-TT2R2 0-1 point and 25 patients - 2 and more points. The scale had low diagnostic value (the square under ROC-curve 0.582), low sensitivity model 0.429 and moderate specificity 0.758 in relation to prediction of residence time in the target range of international normalized ratio 60%. For the value TTR 60% the diagnostic value turned out higher – 0.619 (sensitivity 0.547, specificity 0.789).