Ischemic stroke and vascular cognitive impairment are leading causes of long-term disability and constitute a major public health burden and a significant economic burden to health systems. An increasing body of evidence demonstrates that disorders of glucose metabolism including diabetes, and the intermediate states of impaired fasting glucose and impaired glucose tolerance, as well as the cluster of risk factors known as the metabolic syndrome, are important risk factors for ischemic stroke. The associations with accelerated cognitive decline and dementia are also discussed. Underlying pathogenetic mechanisms are myriad but include insulin resistance, endothelial dysfunction, dyslipidemia, chronic inflammation, procoagulability, and impaired fibrinolysis. The high risk associated with diabetes and other disorders of glucose metabolism carries important implications for preventive strategies for cerebrovascular disease and vascular cognitive impairment that are currently under investigation.