SUMMARY THE AIM of the investigation was to study especially and communications of functional state of kidneys in patients with chronic heart failure different classes with atrial fibrillation. PATIENTS AND METHODS. 75 patients with CHF (43-male, 32-female, mean age 59 ±12 years) were evaluated. The cause of CHF in 18 (24%) patients was arterial hyperpressure, in 24 (32 %) –IHD, in 33 (44 %) their combination and 37 (49 %) patients had myocardial infarction. The speed of glomerular filtration (SGF) was counted by MDRD formulae. 28 patients had persistent atrial fibrillation. RESULTS. SGF was 67,6±18,7 ml/min/1,73 m2 and in 25 (33 %) patients it was<60 ml/min/1,73 m2. In most patients – 51 (68 %) of the left ventricular ejection fraction stayed the same (EF>50%). Patients with decreased kidney function had higher diameter of the left ventricular. SGF was lower in patients with AF, than without AF (57,6±15,3 against 68,2±17,6 ml/min/1,73 m2, accordingly, р<0,001). CKD and functional class CHF were independently associated with atrial fibrillation. CONCLUSION. So the predisposes to atrial fibrillation in patients with chronic heart failure.