AbstractConsistent with principles of developmental psychopathology, this paper presents a broad psychodynamic structural developmental perspective that establishes conceptual continuities between processes of normal personality development, personality organization, concepts of psychopathology, and processes of therapeutic change. The major assumption of this approach is that personality development proceeds in a dialectic synergistic interaction between the development of capacities for interpersonal relatedness and the development of self-definition or identity. Extensive research demonstrates that these two dimensions define two broad types of personality organization, each with a particular experiential mode; preferred forms of cognition, defense, and adaptation; unique qualities of interpersonal relatedness and specific types of object and self-representation. Severe disruptions of this normal dialectic developmental process result in various forms of psychopathology organized in two basic configurations in which there is distorted defensive preoccupation, at different developmental levels, with one of these polarities (relatedness or self-definition) at the expense of the development of the other dimension. This paper reviews empirical findings supporting this approach to normal and disrupted personality development throughout the life cycle and considers its relationship to the internalizing–externalizing distinction in childhood and adolescence, attachment theory, and research on the interaction between biological and psychosocial factors in development across the life span. Finally, we discuss the implications of this approach for intervention and prevention.