Ecological validity, the functional and predictive relationship between a patient's performance on a set of neuropsychological tests and their behavior in a variety of real-world settings, is emerging as a powerful tool. Since neuropsychological data were not designed to be ecologically valid, attempts to use the data in such a manner have been filled with pitfalls. The authors present a strong argument for reevaluating existing tests and/or developing new measurements.Special attention is given to specific functions such as the cognitive constructs of attention, perception, working memory, language, and executive function. Additional consideration is given to the assessment of special populations: children, minorities, substance abusers, elderly, and emotionally disturbed neurological populations.One area in which neuropsychology can lend tremendous assistance is in predicting a client's ability to resume activities of daily living, but more important, when a client can return to work. Ecological Validity of Neuropsychological Testing covers this issue extensively and details the role of vocational rehabilitation and the lack of exposure many within neuropsychology have to these specific needs of their clients.