The study, a subproject within a SCOR in Thrombosis, should help to improve the long-term clinical outcome of patients with proximal deep-vein thrombosis (popliteal, femoral or iliac vein thrombosis) by improving their survival and reducing morbidity from recurrent thromboembolic events, and should help to determine if one or more specific biochemical measures, including antiphospholipid antibodies and activated factor VII, will define a subset of patients at increased risk of recurrent venous thromboembolism.