Thromboses affecting venous superficial system have been considered as benign diseases. Recent studies demonstrate that they might be associated with more severe venous events (as deep venous thrombosis [DVT] or pulmonary embolism [PE]), initially or during 3-month followup. The POST study presents clinical evolution of 844 patients with superficial venous thrombosis (SVT) of lower limbs. Of note, concomitant DVT and/or symptomatic PE were initially found in one quarter of them. Among the 586 patients with isolated SVT (i. e. without DVT or symptomatic PE, and at more than 3 cm of the saphenofemoral junction), 10% presented with DVT, PE, recurrent or extensive SVT during the 3-month follow-up. These results, as the heterogeneous therapeutic management, were confirmed by another cohort study (OPTIMEV). In the CALISTO study, Fondaparinux, at a dose of 2.5 mg once a day for 45 days was effective in the treatment of patients with isolated SVT of the legs and did not have serious side effects. In absence of contra-indication, this treatment may be preferred in patients with confirmed isolated SVT of lower limb.