Antiphospholipid syndrome is the most frequent cause of acquired thrombophilia. Aspirin may have some indications. CURRENT KONWLEDGE AND KEY POINTS: The usefulness of low doses of aspirin is now well demonstrated in the prevention of obstetric complications associated with antiphospholipid antibodies (especially pregnancy loss). When heparin is combined with low-dose aspirin, the recurrent rate of fetal loss is lower than 30%. In patients with arterial or venous thrombosis, there is a high rate of recurrence during the two first years except if high-dose warfarin was used (i.e., INR > or = 3). The association warfarin-aspirin in secondary prevention of thrombosis may be evaluated in prospective studies. It is not so clear in the literature and in our experience that warfarin is superior to aspirin in stroke recurrence prevention in patients with antiphospholipid antibodies, except in Sneddon's syndrome. There are no guidelines in primary thrombosis prevention in patients with antiphospholipid antibodies. In lupus patients, aspirin may not be sufficient after many years of follow-up in preventing a first episode of thrombosis. Prospective studies may be undertaken. Atherosclerotic patients with antiphospholipid antibodies are particularly exposed to the risk of thrombosis after revascularisation or angioplasty and stent implantation. Aspirin may have a place in those patients but these must be evaluated. FUTUR PROSPECTS AND PROJECTS: Except in prevention of obstetric complications, the usefulness of aspirin in patients with antiphospholipid antibodies must be evaluated in prospective studies.