The necessity of anticoagulant treatment after a pulmonary embolus or a deep venous thrombosis has been demonstrated. The modalities of this treatment have been well established, especially the usefulness of initial heparin therapy followed by a period of antivitamin K treatment with an "ideal target INR" between 2 and 3. One of the last questions in this therapeutic protocol is the duration of antivitamin K treatment. The choice of duration of treatment must be made on numerous criteria. It is necessary to distinguish the circumstances of the occurrence of the DVT or the PE and the context. It is thus possible for less than 3 months treatment in secondary venous thrombo-embolic disease, which occurs in precise, recognised circumstances for which the cause will have been controlled. Otherwise, in so-called idiopathic venous thrombo-embolic disease, which is distinguished by a higher prevalence of recurrences, it is known that long-term antivitamin K treatment is effective for the thrombo-embolic recurrences but at the price of a risk of haemorrhage. Finally thrombo-embolic recurrences also benefit from a long treatment. These circumstances of occurrence are thus important in order to decide the choice of treatment duration. But, in our opinion, the compliance to antivitamin K treatment remains the primary criterion to consider. The dilemma facing the prescriber is to evaluate the risk-benefit ratio of each patient, asking especially if the antivitamin K treatment surveillance of a particular patient will be done as well as in the randomised studies. For the future, long-term antivitamin K does not perhaps represent the only therapeutic option. The results of studies evaluating the durations of long-term treatment with less intense levels of anticoagulation (INR < 2) as well as therapeutic alternatives to antivitamin K (antiaggregants or other antithrombins) are awaited.