Cerebrovascular disease is an important cause of cognitive Impairment and dementia in elderly patients. This review highlights the challenges involved in examining the role of cerebrovascular disease In dementia, areas in which consensus is emerging, and an operational framework for clinicians. Two important challenges exist. First, there is no accepted neuropathologic scheme for quantitating cerebrovascular disease In cognitive disturbances. Second, agreement on clinical definitions of vascular dementia is incomplete. Despite the barriers posed by these 2 deficiencies, many consistencies in the clinical, imaging, epidemiological, and neuropathologic aspects of cerebrovascular disease and cognitive impairment have been Identified. Different levels of cerebrovascular disease related to cognitive impairment can be suggested on clinical and Imaging grounds. The overlap between cerebrovascular disease and Alzheimer disease produces a disorder that might be amenable to therapeutic approaches based on either mechanism.