Deep vein thrombosis is a frequent disease with an annual incidence reaching 5 per thousand among subjects over 75 years. Major acquired risk factors for venous thrombosis include surgery, neoplasm, reduced mobility or paresis, and a previous episode of deep vein thrombosis. Among women, hormonal status (pregnancy, oral contraceptive, hormone replacement therapy) is responsible for the majority of all venous thrombotic events. The impact of other factors is controversial: obesity, tobacco use and varicose veins. Venous thrombosis is a multifactorial disease and analysis of the interactions between acquired and inherited risk factors is an extremely interesting field of investigation.