Atrial fibrillation is associated with a prothrombotic state and endothelial dysfunction. To understand whether the prothrombotic state was correlated with endothelial dysfunction and whether the latter was related to atrial dimension (endocardial damage), we studied systemic hemocoagulative activity and markers of endothelial dysfunction in 45 patients with chronic nonrheumatic atrial fibrillation and in 35 controls. We assessed fibrinogen, antithrombin III, protein C, markers of platelet activation (platelet factor 4 and beta-thromboglobulin) as markers of fibrinolysis, and D-dimer, tissue plasminogen activator, plasminogen activator inhibitor, von Willebrand's factor and soluble thrombomodulin as endothelial dysfunction. Plasma fibrinogen (P<0. 005), platelet factor 4 (P<0.001), thromboglobulin (P<0.001), D-dimer (P<0.03), tissue plasminogen activator (P<0.006), plasminogen activator inhibitor (P<0.04) and both von Willebrand's factor (P<0.0001) and soluble thrombomodulin (P<0.03) were significantly higher in the patients than in the controls. Positive significant linear correlations were found between fibrinogen and markers of endothelial dysfunction and left atrial volume and fibrinogen or markers of endothelial dysfunction. These findings confirm that chronic nonrheumatic atrial fibrillation is associated with a prothrombotic state but also suggest that there is a correlation between endothelial dysfunction, coagulation factors and left atrial dimension.