Neuropsychological assessment potentially subserves several functions in subjects in whom Alzheimer's disease (AD) is suspected. Such assessment can detect the presence of brain disease once significant neuronal disruption has occurred. Analysis of the pattern and evolution of cognitive deficits allows inferences to be drawn regarding the likely underlying pathology. Neuropsychological assessment enables delineation of the particular cognitive strengths and weaknesses of individual patients, facilitating the construction of individual management programs. Lastly, cognitive testing provides a cost-effective means of monitoring disease progression and the effects of treatment. This review describes the typical pattern and evolution of cognitive deficits in AD, outlines a number of variant presentations, discusses the differential diagnosis from other dementias, and addresses the issue of progression to clinically probable AD in the cognitively impaired, non-demented elderly. It is anticipated that biomarkers for AD will complement neuropsychological assessment by enabling disease detection before unequivocal cognitive deterioration has ensued, and by improving the accuracy of clinical diagnosis of dementia type. The development of reliable biomarkers will also enable improvements in the sensitivity and accuracy of neuropsychological assessment in AD to be made, more quickly and efficiently than is currently possible using longitudinal studies.