The developmental approaches to psychopathology and self-image reviewed in this article as well as Zigler's broad body of research on mental retardation owe a primary theoretical debt to organismic developmental theory (e.g., Werner, 1948; 1957; Werner & Kaplan, 1963). The research and the formulations of the developmental approach to adult psychopathology that unfolded over the course of more than 40 years demonstrate the power of organismic-developmental theory for understanding and interrelating many major variables in psychopathology. The application of developmental theory has enabled the generation and testing of hypotheses about premorbid social competence, symptomatology, diagnosis, paranoid-nonparanoid status in schizophrenia, prognosis, outcome, and self-images as personality variables. This has created a broad body of data through which these diverse phenomena can be integrated and understood in relation to each other. With respect to psychopathology as well as other aspects of behavior, the developmental framework has allowed the functioning of people with mental retardation to be understood and integrated with the broad body of knowledge about the functioning of people without mental retardation.