Cardiovascular disease (CVD) is a leading cause of mortality.1 For example, in 2000, it accounted directly for around 2 million deaths in the European Union. Worldwide, many people take aspirin daily in the belief that doing so helps to prevent CVD. This approach is established for the secondary prevention of recurrent vascular events. However, there has been some uncertainty about the place of aspirin for the primary prevention of cardiovascular events.6 In particular, there have been doubts about whether any benefits of aspirin in people with no history of CVD outweigh the risks (e.g. the fact that long-term low-dose aspirin therapy almost doubles the likelihood of gastrointestinal haemorrhage). Here we consider the place of low-dose aspirin in primary prevention of CVD.