The discovery of rTAP has provided a wealth of important scientific information ranging from the structural and kinetic characterization of a novel serine protease inhibitor to the importance of factor Xa in the thrombotic process. The results obtained with this inhibitor thus far have broadened our understanding of hemostasis and thrombosis and ultimately may result in the development of newer and more efficient therapeutic agents to combat one of the leading causes of morbidity and mortality in man today.