Treatment with aspirin in patients at high risk of occlusive vascular disease, reduces the risk of serious vascular events (non-fatal myocardial infarction, non-fatal stroke, death from vascular causes) (BMJ 1994, 308: 81-106; BMJ 2002, 324: 71-86). When you start treatment with aspirin you must also consider the risk of bleeding. In secondary prevention, the benefit of treatment with aspirin exceeds the risk, while in primary prevention the cost-benefit is less clear. Current guidelines recommend the use aspirin in primary prevention in people at risk for coronary heart disease (Ann Intern Med 2009; 150: 396-404; Circulation 2002; 106: 388-91; Heart 2005; 91 (suppl 5): v1-52). Also, because age is considered as one of the major determinants of coronary heart disease risk, it is suggested to begin the intake of aspirin above a certain age (2005, 330: 1440-41; Heart 2008; 94: 1429-32; BMJ 2003; 326: 1419). Of course the alternative to starting a treatment in primary prevention is to wait for the event. The negative aspect is that this event could be fatal or very disabling for the person, the benefit of waiting to treat is that this reduces the risk of brain hemorrhage or major extracranial bleeding. The authors conducted a meta-which included six trials of primary prevention (95,000 individuals with a low average risk, 3.554 serious vascular events) and 16 trials in secondary prevention (17,000 individuals with a high average risk, 3.306 serious vascular events) on the long-term treatment with aspirin versus control. The results were as follows: 1) in trials in primary prevention has been a decrease of 12% of serious vascular events (0.51% vs. aspirin vs 0.57% control per year); 2) for mortality in primary prevention has not been a difference statistically significant; 3) an increase in primary prevention of intestinal and extracranial bleeding (0.10% vs 0.07% per year); 4) in secondary prevention a significant reduction of serious vascular events (6.7% vs 8.2% per year); 5) in secondary prevention is not a significant increase in hemorrhagic stroke; 6) in trials in primary and secondary prevention the reduction of serious vascular events was similar in men and women. The authors conclude by saying that more trials are needed, which are in progress, to solve definitively the question of cost / benefit of treatment in primary prevention.