An overview of the risks and benefits of aspirin therapy in primary prevention of cardiovascular diseases (ischemic heart disease, thromboembolic complications of atrial fibrillation, pulmonary embolism...) in the light of old and new evidence. (1-3) For decades it has been considered that aspirin can prevent myocardial infarction and stroke. And until recently, despite the unconvincing evidence, primary prevention trough aspirin was thought to be a sensible treatment strategy. Meta-analyzes on this topic have even indicated that it might be beneficial in terms of reducing overall mortality and reducing the risk of colon cancer. This year, three major prospective studies on the role of aspirin in primary prevention of cardiovascular disease in patients at risk (ASPREE, ASCEND and ARRIVE) have been published, with not only no evidence of benefit compared with placebo but also significant negative consequences (gastrointestinal bleeding) and even a paradoxical increase in mortality. Also, despite convincing evidence, there is still an unusually prevalent use of aspirin in the prevention of thromboembolic complications of atrial fibrillation. Possible reasons for this are multiple.