The concept of adaptation is approached from several directions: (1) a discussion of the meanings of adaptation; (2) a functional socio-cultural set of considerations on which one can base measurement in adaptive behavior; and (3) a practical, applied conceptualization relative to the utilization of the obtained information and the reasons for this type of measurement, and why criterion-referenced measurement is both more logical and more useful to the concept than norm-referenced approaches. The blend between the specific demands of society and the idiosyncratic needs of the handicapped do not fall into systematic or predictable patterns of growth and development. Developmentally disabled persons are not homogeneous, but they do have in common a failure to respond to "necessary and desirable" social demands in an appropriate manner. Once their mode of response is determined, a method of reversal can be developed on an individualized program basis. Appropriate measurement thus becomes the basis for prioritized identification of the reversable aspects of the problem. (Author)