This paper reviews current research concerning psychosocial adaptation to chronic illness and disability and presents recommendations for future development of theories in this area. First, those who craft or adapt theories must use nondisabling, respectful, and empowering language. Rehabilitation professionals must avoid terms that connote pathology, deviance, and abnormality when describing the adaptation to disability process. Instead, they must use language that focuses on the positive, growth-producing aspects of human behavior, which, for example, is the focus of the emerging area of positive psychology. Second, theories should be comprehensible not only to rehabilitation counselors, educators, and researchers, but also to consumers of rehabilitation services. Finally, theories should be based on mathematical models, should lend themselves to prediction, as well as description, and should account for continuous and discontinuous behavior.