Three complexes of importance in psychiatry require clear description: (1) the behavioral response to institutionalization, (2) the personality syndrome of institution-proneness, and (3) the institutional structure and procedure. These complexes are overlapping, so that one must attend to both their common denominators and their differences. 1. Typical Responses to Institutionalization might be stated summarily as follows: (a) claustrophobia and/or claustrophilia; (b) overdependency and/or overindependency; (c) externalized and/or internalized hostility; and (d) rationalization and/or self-incrimination. These responses to institutionalization are often confused with features of the particular deviancy for which the person was institutionalized, such as schizophrenia or criminality. 2. The Institution-Prone Personality shows the following characteristics: (a) immaturity that is rationalized; (b) underachievement and deviancy; (c) the tendency for covert symbiotic relationships; (d) denial of the personal; and (e) extremes of over- and under-compliance with social norms. 3. There are particular sets of counter-dependent-dependent relationships institutionalized in our society that carry over to become the keeper-inmate reciprocals in the total institution. Each inmate is subjected to these reciprocals as part of theinstitutional structure and procedure. His reaction to the influences tends either to increase or decrease his institution-proneness. Depending upon certain variables, he may become rehabilitated or he may be trained to conform to the institutional life.