The laboratory assessment of platelet biology and coagulation has traditionally focused on abnormalities, congenital or acquired, that provide insights for understanding hemostatic defects, unexplained bleeding, and pharmacologic titration of compounds designed to attenuate thrombotic potential. Because atherosclerotic vascular disease is associated with thrombotic events and there exists a clear link between atherosclerosis, inflammation, and thrombosis, the development of markers that have pathobiologic, prognostic, and treatment-related relevance has taken on a role of considerable importance.