This chapter documents the significance of TXA2 and PGI2 in the pathologic events associated with active coronary artery disease. We suggest that altered metabolism of these prostanoids may result in disintegration of platelet and vascular wall reactivities accompanying coronary spasm or intravascular thrombosis associated with myocardial cell necrosis. Further studies should be carried out to determine if coronary circulatory disorders and subsequent myocardial cell injury can be affected by disintegration of the lipoxygenase system that plays a pivotal role in maintaining homeostasis in vascular endothelium and blood components.