Platelets playa fundamental, life-saving role in hemostasis and blood clotting at sites of vascular injury. Unwanted platelet activation and arterial thombus formation are, however, implicated in the onset of myocardial infarction, stroke, and other cardiovascular diseases. Acceptance that platelets play a major role in the pathogenesis of atherosclerosis including coronary heart disease has revolutionized the pharmacological treatment of cardiovascular diseases, and aspirin is now an essential antiplatelet drug and the golden standard for future developments. Yet the search for better and perhaps safer antiplatelet drugs is one of the most active areas of investigation in both basic and clinical research. Platelets, especially human platelets, have also emerged as one of the major models for the study of inter- and intracellular signal transduction pathways. Many biochemists, cell biologists, pharmacologists, pathologists, hematologists, and cardiologists find platelets useful for studying processes such as adhesion, inside-out and outside-in signalling through the plasma membrane, channels, calcium homeostasis, protein kinases, the network of intracellular signal transduction cascades, and the release of vasoactive substances. The aim of the editors has been to compile chapters summarizing the current state-of-the-art information on the biochemistry, cell biology, pharmacology, and physiologic and pathophysiologic roles of human platelets. We hope that this volume represents the major aspects of current platelet research although it is perhaps inevitable that certain areas are covered less thoroughly than others. We would like to acknowledge the excellent help and support of the Springer-Verlag staff, in particular that of Ms. Doris Walker.