THE STUDY WAS UNDERTAKEN TO DETERMINE WHETHER A PRISON TREATMENT PROGRAM INDUCES CHANGES THAT CAN BE CONSTRUED TO CONSTITUTE REHABILITATION AND WHETHER THESE CHANGES ARE RELATED TO PAROLE SUCCESS OR FAILURE. FIVE STANDARDIZED PSYCHOLOGICAL APTITUDE TESTS -- PROGRESSIVE READING, MINNESOTA PAPER FORM BOARD, MECHANICAL COMPREHENSION, CLERICAL SPEED AND ACCURACY, VOCABULARY -AND ONE PSYCHIATRIC TEST -- MINNESOTA MULTIPHASIC PERSONALITY INVENTORY (MMPI) -- WERE ADMINISTERED TO 273 INMATES CONSECUTIVELY RELEASED FROM THE CALIFORNIA INSTITUTION FOR MEN, CHINO, CALIF. THE INMATES' TEST SCORES UPON ADMISSION AND PRIOR TO RELEASE WERE COMPARED. CHANGES IN TEST SCORES INDICATE THAT THE PRISON'S PROGRAM PRODUCES IMPROVEMENTS IN PSYCHOLOGICAL APTITUDE AND IN THE AREA OF PERSONALITY. ON THE BASIS OF THE INMATES' TEST SCORES, AN INDEX OF REHABILITATION IS CONSTRUCTED. THE INDEX COMBINES TWO MEASURES -- AN INDEX OF PERFORMANCE (PSYCHOLOGICAL APTITUDE TEST SCORE CHANGE) AND AN INDEX OF PERSONALITY (MMPI SCORE CHANGES) -- INTO A SINGLE INDEX OF OVERALL CHANGE. THE ABILITY OF THE REHABILITATION INDEX TO PREDICT WHETHER AN INMATE WILL SUCCEED OR FAIL ON PAROLE IS ASSESSED BY EXAMINING THE SUBJECTS' PAROLE RECORDS. IMPLICATIONS OF THE FINDINGS ARE DISCUSSED, AND SUGGESTIONS FOR RELATED RESEARCH ARE OFFERED. SUPPORTING DATA AND A LIST OF REFERENCES ARE INCLUDED. (LKM)