A subarachnoid haemorrhage (SAH) is a type of stroke due to bleeding in the subarachnoid space, which is the small space between the brain and the skull, and which contains blood vessels that supply the brain. The cause of the bleeding is usually a rupture of a bulge in one of these vessels, which is called an aneurysm. The outcome of patients after SAH is generally poor: 50% of patients die within one month after the haemorrhage, and of those who survive the initial month, 50% remain dependent on someone else for help with activities of daily living (eg, walking, dressing, bathing). One of the causes of poor outcome is a complication of SAH called secondary ischaemia (ischaemia means lack of blood). This complication occurs four to 10 days after the haemorrhage (hence secondary). The cause is not exactly known, but besides contraction of the blood vessels in the brain, there is evidence that clotting of blood platelets plays a role as well. Therefore, trials have been performed with agents that prevent clotting of blood platelets (antiplatelet agents). In this review of seven trials, including 1385 patients, that studied the effects of antiplatelet agents on the outcome after SAH, we found that patients who were treated with antiplatelet agents had a poor outcome less often, and secondary ischaemia less often than patients that received no antiplatelet agent, but the results were not statistically significant and so no definite conclusion can be drawn. Moreover, patients who are treated with antiplatelet agents might have a slightly higher risk of bleeding. Based on these results we conclude that antiplatelet agents after SAH cannot be recommended at the present time.