Over the past few years, microparticles (MPs) which are small vesicles originating from the budding of cellular membranes have emerged as important biological entities regulating hemostasis. MPs expose at their surface procoagulant molecules such as phosphatidylserin and tissue factor (TF). All data obtained in mouse models support a role of MPs in venous thrombosis mediated by the TF activation. Moreover, results from clinical studies showed that TF-MPs was associated with the risk of venous thrombosis. However, the predictive value of TF-MPs in the recurrence of VTE is unknown. Besides, no study has taken into account the recent progresses in the understanding of the role of MPs in haemostasis. Indeed, MPs vectorize molecules which are not only procoagulant but also profibrinolytic. The net result depends on a balance between both activities (the coagulo-lytic balance). This balance is can be measured by two complimentary assays on MPs.