P-selectin and P-selectin glycoprotein ligand 1 (PSGL-1) are vascular adhesion molecules that play an important role in leukocyte-endothelial and leukocyte-platelet interaction during the inflammatory response. Their functions are now known to include a role in thrombus formation, specifically in relation to fibrin generation and propagation. Recent findings have demonstrated that leukocyte-derived microparticles, bearing both tissue factor and PSGL-1, circulate in the blood and accumulate in the developing platelet-rich thrombus following vessel wall injury, thus concentrating tissue factor at the site of vascular injury and initiating blood coagulation.