This chapter considers that the mental and personality disorders primarily reflect a deficit, deficiency, or failure in the final stage of ego maturation, namely, in the process of desatellization, which ordinarily takes place mostly in adolescence. It discusses both types of inadequate and immature personality disorder—the basic type indicative of failure in desatellization and the reactive, counter-aggressive type that resembles it only phenotypically— along with: the most common type of narcotic addiction; and the mental disorder. Complicating considerably the interpretation and diagnosis of the maturational condition involving defect or failure in desatellization at adolescence is the existence of a phenotypically very similar condition of maturational failure that, genotypically, is completely different in terms of developmental background and etiology. Despite the superficial resemblance between Process Schizophrenia and Infantile Autism and the prior tendency of child psychiatrists to group these latter disorders together, they are really quite different.