Vascular dementia (VaD) is the second-most-common cause of dementia in the elderly, after Alzheimer's disease (AD). VaD is defined as loss of cognitive function resulting from ischemic, hypoperfusive, or hemorrhagic brain lesions due to cerebrovascular disease or cardiovascular pathology. Diagnosis requires the following criteria: cognitive loss, often predominantly subcortical; vascular brain lesions demonstrated by imaging; a temporal link between stroke and dementia; and exclusion of other causes of dementia. Poststroke VaD may be caused by large-vessel disease with multiple strokes (multiinfarct dementia) or by a single stroke (strategic stroke VaD). A common form is subcortical ischemic VaD caused by small-vessel occlusions with multiple lacunas and by hypoperfusive lesions resulting from stenosis of medullary arterioles, as in Binswanger's disease. Unlike with AD, in VaD, executive dysfunction is commonly seen, but memory impairment is mild or may not even be present. The cholinesterase inhibitors used for AD are also useful in VaD. Prevention strategies should focus on reduction of stroke and cardiovascular disease, with attention to control of risk factors such as hypertension, diabetes mellitus, hypercholesterolemia, and hyperhomocysteinemia.