Platelet microparticles are submicron vesicles that can support thrombin generation on externalized negatively charged phospholipids. Increased numbers of circulating platelet microparticles have been investigated as the basis of hypercoagulability in a variety of prothrombotic conditions. Measurement of platelet microparticles is not standardized and a number of preanalytic considerations can influence accurate analysis. We describe methodology for light scatter-based flow cytometry as well as impedance-based flow cytometry for the enumeration and characterization of platelet microparticles.