Acetylsalicylic acid (ASA) as secondary prophylaxis after ischaemic cerebrovascular events is well established and its efficacy unquestioned since over 15 years. According to the results of two European studies a dose of 100 mg per day is sufficient to reduce the incidence of further stroke, myocardial infarction, and death due to cardiovascular causes. This satisfactory response to low-dose ASA applies to patients with transient ischaemic attacks, reversible ischaemic events, and minor strokes. In cases with severe cardiac disease, however, a high dosage of ASA or anticoagulation therapy may be necessary to prevent further vascular events.