The prevalence of diabetes mellitus (DM) varies from 1.2 to 13.3% in the general population. The most frequent is type 2 (non-insulin-dependent) DM, which constitutes 90-95% of all cases. DM increases the risk of cardiac disease, stroke, retinopathy, nephropathy, neuropathy and gangrene, and the disease is associated with an increased prevalence of other cardiovascular risk factors such as hypertension, hypercholesterolaemia, asymptomatic carotid artery disease, and obesity. The risk of stroke may be directly and indirectly increased by the presence of DM. Epidemiological data show that DM independently amplifies the risk of ischaemic stroke from 1.8- up to 6-fold, so that prevention of cardiovascular risk in diabetics is of utmost importance. The main goal is to control glycaemia, although it has never been shown to be beneficial in stroke patients. Other preventive strategies include antiplatelet treatment. The open-label Primary Prevention Project trial tested the efficacy of low-dose acetylsalicylic acid (ASA) in prevention of ischaemic events in high-risk patients, but failed to demonstrate a significant benefit of ASA in diabetic patients. However, in the CAPRIE trial, the benefit of clopidogrel was amplified in patients with DM versus those without DM in preventing ischaemic events. This difference was even more striking when comparing patients treated with insulin versus non-diabetics. Another trial -- MATCH -- tested the benefit of adding ASA to clopidogrel versus clopidogrel alone in the prevention of ischaemic events in high-risk cerebrovascular patients, two-thirds of whom had DM. Further research is needed to clarify the effects of different antiplatelet regimens in stroke prevention in diabetic patients, who should be considered as high vascular-risk patients.