The recent development of symptomatic pharmacological treatment for Alzheimer's disease (AD) and the probable introduction of new therapies in a near future make the assessment of dementia at its different stages an even greater scientific and public health challenge. Neuropsychological tests, together with clinical data, are at present the only in vivo non-invasive screening and diagnostic tools for AD and related disorders. This chapter reviews the application to AD of standard batteries and short screening tests. It also analyzes the tests to be applied to detect and assess the specific deficits of the disease, and discusses the advantages and flaws of current screening and diagnostic tests of dementia. Emphasis is placed on the need to devise and use tests developed in a rational manner, with high sensitivity and specificity, not only in the moderate stages of the disease, but also in the very early and even "preclinical" stages, as well as during the late stages (severe dementia). It is known that neuropsychological tests allow one to determine various patients' profiles. Future research should determine the possible predictive value of these profiles. This has important implications for therapeutic trials. The current implicit assumption that all patients with AD tend to evolve and decline in a similar fashion needs to be critically re-examined.