Occupational and physical therapists emphasize evaluations and interventions that promote object play and manipulation, mobility, self-care, and social function. Evaluations typically focus on underlying performance components, with emphasis on neuromotor function and the interaction of those components in an environmental context. This article emphasizes theoretic approaches that are widely used in occupational and physical therapy practice with children. Neuromaturational theory, developmental theory, and dynamic systems are described, and assessments that represent those theories are identified. Strategies employed for selection and use of evaluation instruments within these theoretic approaches are defined.