Dementia affects about 5% of the elderly population over age 65 years and has an unexplained predominance in women and a low rate in some cultures. Different forms of dementia are now distinguished-Alzheimer's disease, dementia with Lewy bodies, frontotemporal dementia, and dementia secondary to disease, such as AIDS dementia. However, such nosological boundaries are being re-evaluated because different dementias are believed to have common underlying neuropathology. Neurochemical and neurobiological research has led to advances in understanding causes of dementia, and functional imaging has allowed identification of possible biomarkers; from these, a range of potential treatment approaches have arisen that focus on enhancement of neurotransmitter function, intervention at the level of amyloid production and deposition, and reduction of secondary risk factors such as hypertension, depression, and hypolipidaemia. Molecular diagnostic testing and genetic counselling for families with autosomal dominant early-onset dementia are new developments; however, this approach is not useful for late-onset dementia, in which the identified candidate susceptibility genes have a relatively small effect on risk. While fundamental research works towards new biological treatment strategies, much remains to be done in the area of disease management and the development of appropriate models of long-term care.