Aspirin has public health potential to reduce the risk of ischaemic vascular events and sporadic cancer. One objection to the wider use of aspirin for primary prevention, however, is the undesirable effects of the medicine, which include increasing risk of bleeding and haemorrhagic stroke. Marathons also carry risks of serious events such as cardiac arrests and sudden death. Based on epidemiological estimates, a person running a marathon might be 20 to 100 times more likely to end up in hospital than a person who is taking an aspirin tablet. Yet the cumulative risk of daily aspirin use for primary prophylaxis may be important. One option open to middle-aged individuals who want to take aspirin is to start with an infrequent regime, such as once per week, in order to then build to daily use. It is important to get all concerns into perspective and comparisons can offer a challenge to any excessive risk aversion regarding the public health potential of aspirin.