BACKGROUND Evidence from two surveys in Wales, one of the countries of the United Kingdom, shows that there is an under-use of aspirin for secondary prophylaxis. A rapid health impact assessment of a policy of aspirin promotion in Wales is undertaken, with some estimates on service provision. METHODS In this analysis, a general population approach rather than gender-specific calculations was undertaken to estimate scale of magnitude. Readily available epidemiological data from the Welsh population was combined with effect estimates of aspirin derived from randomised controlled trials (RCTs). RESULTS An additional 700 vascular events may be avoided annually, but the impact of aspirin promotion in the 30-45% of non-compliant individuals might range from 400 to 1200. This relates to about two vascular events being avoided each day if aspirin were used at a maximum level, with 100% compliance. An individual general medical practitioner might case-find 25-35 individuals who should be taking aspirin regularly. DISCUSSION The promotion of aspirin to post-vascular event individuals who are non-compliant might be achieved through routine clinical management of patients. Person-centred approaches to improving compliance might be introduced.