This chapter attempts a systematic application of the dynamics of ego development to the pathogenesis of the behavior disorders. In psychoanalytic theory, "the unconscious" forms the cornerstone of psychopathology. It is the domain of instinctual urges and the locus of repressed libidinal impulses referable to earlier alleged stages of psychosexual development which for some reason had become fixated at a primitive level of evolution. Broadly speaking then with certain notable exceptions, most persons can be divided into two main groups in terms of ego development outcomes and susceptibility or vulnerability to the various mental disorders, namely, satellizers and nonsatellizers. As in man, primary behavior disorders in animals are also caused by psychosocial factors in which neurobiological variables play a mediating role, whereas secondary behavior disorders, as in man, reflect impairment of the neural substrate itself. The causes of frustration and conflict in human beings must also be largely formulated in terms of ego needs.