Because developmental psychology is the study of behavioral ontogeny, it should contribute to our understanding of children's behavior disorders. G. Stanley Hall, the founder of American developmental psychology (Kessen, 1965), envisioned it as a guide to child rearing and the prevention of maladaptive behavior. Child mental-health services, from their inception early in this century, have also stressed the developmental origins of psychopathology (cf. Achenbach, 1981). Yet, experience in child clinical settings and perusal of the developmental literature show little connection between current clinical practice and developmental research. Why?