A cutting-edge review of the latest findings on the complexities of platelet function and the various means of inhibiting platelet clot formation. The authors delineate an up-to-date picture of platelet biology and describe methods for assessing platelet function, including the commonly used platelet aggregation, thromboxane production, procoagulant function, platelet function under flow, and the expression of platelet activation markers. The focus is both on the technology and the outcome of research on platelets, including the fast developing fields of proteomics and genomics and their application to platelet research. The clinical applications of the various methods for the assessment of platelet function in vivo, as well as antiplatelet therapy, are fully discussed.