THE HISTORY AND PURPOSES OF INCARCERATION, THE PHYSICAL AND SOCIAL STRUCTURE OF CONFINEMENT, PSYCHOLOGICAL ADAPTATION TO LIFE IN PRISON, AND THE INEFFECTIVENESS OF VARIOUS TREATMENT MODALITIES IN REDUCING RECIDIVISM ARE DISCUSSED AS FACTORS IN UNDERSTANDING THE PRISON ENVIRONMENT AS A COMPLEX SOCIAL AND POLITICAL SYSTEM THAT EXERTS A POWERFUL FORCE ON HUMAN BEHAVIOR. IT IS NOTED THAT THE GENERAL KINDS OF PSYCHOPATHOLOGY THAT THE PRISON ENVIRONMENT PRODUCES IN INCARCERATED PEOPLE ARE MORE RELEVANT TO AN UNDERSTANDING OF THE PATHOLOGICAL CONSEQUENCES OF THE PRISON EXPERIENCE THAN ARE THE KINDS OF IDIOSYNCRATIC PATHOLOGY THAT SOME PEOPLE MAY BRING INTO PRISONS. FROM THIS POINT OF VIEW, IT IS POSSIBLE TO INTERPRET WHAT APPEARS TO BE ABNORMAL OR DISORDERED BEHAVIOR ON THE PART OF INMATES AS BEING IN REALITY NORMAL, FUNCTIONAL ADAPTATION TO EXTREME, PATHOLOGICAL CIRCUMSTANCES. THE ABSENCE OF LONG-TERM STUDIES ON THE EFFECTS OF OCCUPATIONAL STRESS ON PRISON GUARDS IS NOTED, AS IS THE NEED FOR RESEARCH ON PRISON BEHAVIOR TO BE CONDUCTED BY IMPARTIAL OBSERVERS. A SIMULATION STUDY (NCJ 10301) IS CITED IN WHICH STUDENTS PLAYED ROLES AS GUARDS AND PRISONERS FOR A 2-WEEK PERIOD. HALF OF THE MOCK PRISONERS HAD TO BE RELEASED WITHIN 5 DAYS BECAUSE OF SEVERE EMOTIONAL DISTRESS. ALL OF THE MOCK GUARDS AT SOME TIME BEHAVED CRUELLY, BRUTALLY, AND SADISTICALLY. THE ENTIRE EXPERIMENT HAD TO BE TERMINATED PREMATURELY BECAUSE THE SUBJECTS APPEARED TO HAVE LOST SIGHT OF THE BOUNDARY BETWEEN ROLE IDENTITY AND SELF-IDENTITY. THIS AND OTHER RESEARCH IS SAID TO POINT TO THE FORCES THAT TOTAL INSTITUTIONS BRING TO BEAR IN MODIFYING BELIEFS, PERCEPTIONS, VALUES, AND BEHAVIOR. A LIST OF REFERENCES IS INCLUDED.