ABSTRACT: Although formal assessment of children with severe disabilities raises many problems of measurement, evaluation by “standard rulers” is essential lest conclusions about disabled youngsters’ potential development be drawn solely by observation. Repertoires of behavior are observed and evaluated with both commonly-used instruments and some specifically designed for handicapped populations. Specialized techniques of administration and analysis can be employed to yield a profile of functional strengths and weaknesses. Data regarding cognitive, perceptual, motor, language, and social domains may be obtained with findings synthesized to provide specific recommendations for appropriate training strategies. Interventions are then prescribed to foster optimal growth and learning.