In humans, hyperglycemia during acute stroke has been associated with inferior clinical outcomes. Intravenous insulin infusion is the common method for effectively lowering and controlling hyperglycemia exceeding 180 mg/dL during acute illness. Diabetes is a clear risk factor for stroke, so it is reasonable to strictly control diabetes using the local guidelines for the prevention of stroke recurrence without any contraindications. The risks of Alzheimer`s disease and vascular dementia are increased in diabetics. Glycemic control plays an important role in the preservation of cognitive performance in patients with diabetes. However, glycemic control in dementia patients is neglected by many physicians. We recommend the same glycemic targets for dementia patients as for general diabetic patients without a high level of functional dependency or a limited life expectancy. (Korean Clinical Diabetes J 11:291-293, 2010)