The essential role of human platelets in hemostatis and circulation is well recognized. Basic research of the last two decades has clearly established that platelets play a major role in hemorrhagic/thrombotic and cardiovascular diseases including atherosclerosis and cerebral/myocardial infarction. Very recently, important advances in our understanding of platelet structure, function and regulation at the molecular level have been made. Particularly, advances in our understanding of the physiology, pathophysiology and pharmacology of adhesion receptors have paved the way for novel, innovative therapeutics. This book highlights areas of platelet physiology, pathophysiology and pharmacology in which our understanding of the molecular structure, function and regulation is rapidly expanding.