The aim of platelet inhibitory therapy in cardiology is to prevent undesired thrombus formation and, thus, to prevent complications of cardiovascular diseases. In Germany, 5 substances are approved for antiplatelet therapy. Acetylsalicylic acid, an inhibitor of platelet cyclooxygenase, has been shown to be effective at both high and low doses in the secondary prevention of myocardial infarction, coronary heart disease, and cerebrovascular disease. In addition, acetylsalicylic acid is effective in reducing the complications of unstable angina pectoris and coronary angioplasty, and in reducing the occlusion rate of aortocoronary bypass grafts. The addition of dipyridamole to acetylsalicylic acid has not been shown to result in any additional benefit in many clinical studies. Ticlopidine, an antagonist of ADP-induced platelet aggregation has been similarly effective as acetylsalicylic acid in the treatment of coronary heart disease. The principal side effect of the drug, the occurrence of neutropenia in about 1% of treated patients, makes regular blood cell counts mandatory during treatment. In the secondary prevention of cerebrovascular disease, the drug may be superior to acetylsalicylic acid. Trapidil is an anti-platelet substance which acts on platelets through various mechanisms including inhibition of the release of "platelet derived growth factor". In 3 smaller randomized studies, trapidil has been found to reduce the restenosis rate after coronary angioplasty. Abciximab, the Fab-fragment of an antibody against the platelet fibrinogen receptor glycoprotein 11b/IIIa has been shown to be effective in the prevention of acute and long-term complications of high-risk coronary angioplasty.