Microparticles released from cells (MPs) may play a role in the normal hemostatic response to vascular injury and a role in clinical diseases because they express phospholipids, which function as procoagulants. Although flow cytometry is the most widely used method for studying MPs, some novel assays such as tissue factor-dependent procoagulant assay or the ELISA method have been reported. However, the use of MP quantification as a clinical tool is still a matter of debate. Elevated platelet-derived MP, endothelial cell-derived MP, and monocyte-derived MP concentrations are documented in almost all thrombotic diseases occurring in both venous and arterial beds. However, the clear significance of MPs in various clinical conditions remains controversial. For example, it is not known if MPs found in peripheral blood vessels cause thrombosis, or whether they are the result of thrombosis. On the other hand, numerous studies have shown that not only the quantity but also the cellular origin and composition of circulating MPs are dependent on the type of disease, the disease state and medical treatment. In addition, many different functions have also been attributed to MPs. Thus, the number and type of clinical disorders associated with elevated MPs is currently increasing.