This chapter discusses the factors affecting athlete development in parasport and highlights several important areas for future work. Performer constraints are mental and physical characteristics that are embodied in an individual, and have two general subdivisions: structural constraints, which relate to body structure, and functional constraints, which are behavioural characteristics. Task constraints relate to the goal of the task, and the rules that constrain possible responses. In all sports, there are specific rules and policies that regulate the types and amounts of specific behaviours demonstrated in competition. The most obvious constraint in parasport that makes it unique from non-parasport is the issue of classification. Classifications in Paralympic individual sports reflect the unique individual limitations that need to be accommodated. Because classification of an athlete's impairment can vary so considerably, team sports have created rules to standardize the performance environment to prevent any team from taking advantage. Environmental constraints are those that generally do not change the nature of the task.