Objective:To determine whether CA-125 is elevated in medically stable patients with chronic atrial fibrillation (AF) compared with patients without AF and to examine whether levels of CA-125 are associated with demographic and clinical variables in a sample of patients under study.Methods:55 patients with chronic AF and 58 control patients in sinus rhythm were included into the study.Patients with acute heart failure (HF),chronic inflammatory or neoplastic disease were excluded from the study.Circulating levels of CA-125 were assessed; all patients underwent clinical examination,assessment and medical records including demographic data,history of comorbid conditions,current use of cardiac medications,and the results of cardiac tests including electrocardiograms.Results:The mean age of the study sample was 53.2±6.5 years and 48％ were men.Patients with sinus rhythm were significantly more likely to have lower heart rates,smaller dimensions of left atrium,and to be treated with aspirin.Coumadin,coumadin and digoxin were more often prescribed in patients with chronic AF.The CA-125 levels were significantly higher in patients with chronic AF than in patients in sinus rhythm (48.5±7.65 U/ml and 28.43±5.48 U/ml,P＜0.005).An inverse relation was found between CA-125 levels and left ventricular ejection fraction (LVEF) (r=-0.48,P＜0.001).CA-125 was significantly related to the left atrium (LA) diameter,left ventricular end-diastolic diameter (LVEDD),left ventricular end-systolic diameter (LVESD) and brain natriuretic peptide (BNP).There was no significant correlation between CA-125 and age.Conclusion:In subjects with chronic AF,CA-125 levels are increased; CA-125 was significantly related to the LA diameter,LVEDD,LVESD and BNP.