Inhibitors of thrombocyte aggregation are generally accepted in the therapy and prophylaxis of ischemic cerebrovascular disease. The frequency of re-infarction, morbidity and mortality after TIA, PRIND and minor stroke is influenced favourably. There are controversial opinions, however, about the usefulness for patients suffering from completed strokes. In patients with progressive stroke, cerebral embolism of cardiac source, or non-infective thrombosis of sinuses or cerebral veins, inhibitors of thrombocyte aggregation are used if anticoagulation therapy is not possible. Additionally, they are applied in cases of infective thrombosis of sinuses or cerebral veins, after termination of anticoagulation therapy, after cardiac valve replacement, and after surgical reconstructions of craniocervical vessels. Acetylsalicylic acid is the clinically best examined substance; its effect--especially in males--was proven by numerous prospective trials. A combined treatment with dipyridamole, sulfinpyrazone or other drugs seems to be unnecessary. A daily dose of not more than 300 to 325 mg acetylsalicylic acid is recommended for prophylaxis after ischemic cerebral events; in connection with that dose severe gastrointestinal side effects are hardly to be expected. Whether even lower doses would yield the same prophylactic effects will have to be clarified by further studies.