As spinoffs of the current revolution in the cognitive and neurosciences, clinical neuropsychologists in the 21st century will be employing biological tests of intelligence and cognition which record individual differences in brain functions at the neuromolecular, neurophysiologic, and neurochemical levels. Assessment of patients will focus more on better use of still intact functions, as well as rehabilitating or bypassing impaired functions, than emphasizing diagnosis, as is the focus today. Better developed successors to today's scales for assessing personal competency and adaptive behavior, as well as overall quality of life, also will be in wide use in clinical settings. With more normal individuals, use of new generations of paper and pencil inventories as well as biological measures for assessing differences in interests, attitudes, personality styles, and predispositions is predicted. Two figures and one table illustrate the discussion, and a 63-item list of references is included. (Author/SLD)