Vascular disease is the second commonest cause of dementia after Alzheimer's disease. There are difficulties in classifying patients with this type of cognitive impairment owing to varied clinical presentation and different types of arterial disease. There is some degree of overlap in the neuropathology of Alzheimer's and vascular dementia. Deficient cholinergic neurotransmission, a characteristic of Alzheimer's disease, has been postulated to contribute to the cognitive impairment of vascular disease of the brain. Cholinesterase inhibitors, such as donepezil, may therefore be a rational treatment.