Large-scale trials have shown that primary prevention using acetylsalicylic acid is useful in all patients with a cardiovascular risk exceeding 1.5% annually. In these patients the benefits of prevention outweigh the risks of bleeding. Almost all patients with diabetes mellitus are at high risk of developing cardiovascular disease. Additionally, most diabetics have other cardiovascular risks besides diabetes, providing further argument for prevention with acetylsalicylic acid. Only very few prospective trials have confirmed that acetylsalicylic acid treatment in patients with diabetes mellitus reduces their risk of cardiovascular disease and myocardial infarction. Treatment with acetylsalicylic acid should be considered in all patients with diabetes, especially in view of their decreased survival after a cardiovascular event, myocardial infarction in particular. If acetylsalicylic acid is contra-indicated treatment with clopidogrel is an alternative.