Chronic atrial fibrillation (AF) has often been associated with systemic embolization, and patients with mitral stenosis (MS) have the highest thromboembolic risk. Increased risk of thromboembolism could be in part due to impaired fibrinolytic function. Global fibrinolytic capacity (GFC) is an innovative technique for evaluating the entire fibrinolytic system. The aim of our study was to evaluate fibrinolytic activity in patients with rheumatic and nonrheumatic chronic AF To investigate fibrinolytic activity, we assessed GFC in peripheral blood samples of 32 patients with nonrheumatic AF (14 women; mean age, 56 +/- 1 years), 30 patients with rheumatic MS and AF (23 women; mean age, 35 less than or equal to 9 years), and 32 patients with rheumatic MS and sinus rhythm (24 women; mean age, 36 +/- 8 years). The control group comprised 30 healthy adult subjects in normal sinus rhythm. Patients with chronic AF (rheumatic and nonrheumatic) had lower GFC than did the controls (P =.0001). The rheumatic AF group also showed decreased levels of GFC compared with the nonrheumatic A-F group, with the rheumatic MS and sinus rhythm group, and with controls (P =.03, P =.02, P =.0001, respectively). GFC was lower in patients with rheumatic MS and sinus rhythm than in controls (P =.003). Although there were correlations between GFC and mitral valve area, transmitral mean gradient, left atrial diameter, and mitral calcification in patients with rheumatic MS, multivariate analysis showed only transmitral gradient as an independent factor affecting GFC. Patients with AF have decreased GFC, a finding that suggests the presence of a hypofibrinolytic state. Fibrinolytic dysfunction was more pronounced in rheumatic MS patients with AF than in those with nonrheumatic AF. Moreover, patients with rheumatic MS and sinus rhythm had decreased global fibrinolytic activity. Hypofibrinolysis documented by decreased GFC can be one of the important causes of increased risk of embolism in patients with A-F and rheumatic MS.