A 27-year-old man was admitted to our hospital with the complaints of swelling of his face and lower limbs. Echocardiography showed minimal pericardial effusion accompanied by disordered diastolic function. Cardiac catheterization was performed to rule out constrictive pericarditis. Normal pressure tracings of the right heart rule out constrictive pericarditis, however, a. narrowing of the inferior vena cava was observed. Venographies of the inferior and superior vena cavae showed extensive thrombotic involvement of these great veins. Protein C, protein S, anticardiolipin antibodies, fibrinogen, antithrombin-III, activated protein C resistance, and factor V levels were in normal limits. Heterozygosity for factor V Leiden mutation was detected. We conclude that factor V Leiden mutation can cause extensive thrombotic involvement of major veins and should be considered in idiopathic thrombosis of them.