The purpose of this article is to provide the reader with an orientation to the concepts and principles of autonomy and self-determination and the application of those concepts and principles to working with children and adolescents who have intellectual and developmental disabilities (ID/DD), including autism. Self-determination is essentially the ability of a person to be autonomous as to meaningful life choices and encompasses activities such as problem solving, decision making, goal setting, self-observation and evaluation, self-management and reinforcement, acquiring an internal locus of control, experiencing positive attributions of efficacy and outcome expectancy, developing a realistic and positive self-image, and self awareness. The lack of opportunities for self-determination, personal expression and consideration of personal preferences experienced by this population has been associated with increased psychiatric disturbance. Several principles supporting self-determination, including positive psychology and use of positive alternatives, are discussed by the authors. Further, practices that generate more opportunities for individuals to exercise personal control and autonomy across activities and environments in order to prevent psychological problems are discussed. Finally, the school psychologist's role in promoting the development of autonomy and self initiative among children and adolescents with ID/DD are outlined within the contexts of assessment practices, interventions and curriculums, positive behavior support technology, and continued educational reforms and systems change. (Contains 1 table.)