It is increasingly apparent that each form of dementia has a distinct cognitive profile, and that this reflects the pattern of underlying neuropathological change. Advance in the understanding of the neuropsychology of the dementias has led to a greater role for neuropsychological assessment in the diagnosis and treatment of the various neurodegenerative diseases. A full neuropsychological battery produces a much wider range of scores and taps more cognitive domains, making early detection possible and providing differential diagnosis within the dementias. It is non-invasive, well tolerated by patients, relatively inexpensive, and most importantly, it may be sensitive to the prodromal phase often seen in dementia. In this review, a brief outline of the rationale for neuropsychological assessment is given, together with a description of what a detailed neuropsychological assessment can offer a clinician over and above simple rating scales such as MMSE and ADAS-cog.