Fibrinolytic efficiency in the treatment of deep venous thrombosis is superior to heparin efficiency, but appears as more expensive. It must thus been used only if strongly required. Thrombolytic role is then demonstrated on the clot lysis, as far as the latter is recent, near, and not really obstructive. Such a thrombosis can be performed such a treatment, thus reducing sequelae of post-phlebitic disease. However, it increases by 2.9 the hemorrhagic risk, thus requiring extreme caution as for fibrinolysis and by 70 for SK and up to 200 for UK as for the cost. On a practical point of view, using SK (100,000 U/h) UK (4,000 U/kg/h) after an initial dose or UK (2,000 U/kg/h) combined with heparin, the treatment will be performed at least three days and followed up every 6 hours thanks to a fibrinemia, biological control as for therapeutic efficiency, numeration and a TCK. Fibrinolytics are thus prescribed to young patients presenting with a recent phlebitis demonstrated thanks to phlebography.