Extracellular vesicles (EVs) are small (<1 μm in diameter) particles surrounded by bilipid membranes that carry DNA, RNA, proteins, and other intracellular molecules from the cell that released the EV to a recipient cell—facilitating intercellular communication. EVs are naturally released by all types of cells in response to injury or cell death, with the aim of eliciting help from their surroundings to aid in cellular debris removal and tissue repair. The type of signals that induce EV release (i.e., injury vs apoptosis) can change the makeup of the EV membrane surface, sometimes resulting in EVs that have a more procoagulant phenotype, which is often manifested by phosphatidylserine (PS) exposure and/or tissue factor (TF) expression. These procoagulant EVs potentiate thrombosis and are associated with an increased risk of both arterial and venous thromboembolism. The goal of this chapter is to provide information and protocols with which to evaluate the procoagulant potential of EVs derived from cells in the vasculature, where prothrombotic activity can cause the most harm.