The role of antiplatelet therapy (chiefly aspirin) for the secondary prevention of heart attacks and strokes is firmly established for many high-risk people with diagnosed arterial disease, and the proportional reductions in these cardiovascular events appear to be about one quarter, whether or not such patients have diabetes. But, most younger and middle-aged people with diabetes do not have manifest arterial disease - although they are still at significant cardiovascular risk - and yet few trials have tested aspirin in such individuals. As a result, there is substantial uncertainty about the role of aspirin for the prevention of heart attacks and strokes among apparently healthy people with diabetes, and only a small minority receives it.