The paper discusses current views on the mechanisms of acetylsalicylic acid action, its pharmacokinetics, adverse effects, the issue of resistance and its benefit in clinical practice. Inthe primary prevention, long-term administration of medication containing acetylsalicylic acid (ASA) has been proven to favorably influence only the incidence of myocardial infarction in secondary prevention, it also lowers the occurrence of repeat strokes and transitent ischemic attacks (TIAs) by 13–25 %. In the treatment of acute ischemic stroke, the initial dose of 160–325 mg ASA is recommended within 48 hours from the stroke, since it lowers – mildly but significantly – the probability of early recurrence of ischemic stroke. After lengthy discussions and repeated experimental, pharmacological and clinical studies, the currently recommended dose for secondary prevention of stroke/TIA is 50–325 mg ASA daily.

        Key words: acetylsalicylic acid, adverse effects, aspirin resistance, primary prevention, secondary prevention, acute stroke, dose height