A SERIES OF STUDIES WAS UNDERTAKEN WITH A SAMPLE OF OVER 2,000 OFFENDERS, 18 TO 27 YEARS OLD, AT THE TALLAHASSEE FEDERAL CORRECTIONAL INSTITUTION (FLORIDA). THUS FAR THESE STUDIES HAVE DEMONSTRATED THAT THE MMPI PROFILES OF YOUTHFUL OFFENDERS FALL INTO DISTINCT CLUSTERS, THAT CLINICIANS CAN RELIABLY SORT MMPI PROFILES INTO THESE GROUPS, THAT OPERATIONAL DEFINITIONS FOR THESE GROUPS MAY BE FORMULATED WHICH ENNABLE A CLINICIAN OR A COMPUTER TO RELIABLY ASSIGN MMPI PROFILES TO 10 DISTINCT GROUPS, THAT YOUTHFUL OFFENDERS SO CLASSIFIED DIFFER SIGNIFICANTLY ACROSS GROUPS IN A WIDE VARIETY OF SOCIOPSYCHOLOGICAL AND DEMOGRAPHIC VARIABLES, AND THAT THESE DIFFERENCES IMPLY DIFFERING TREATMENT SETTINGS AND TREATMENT STRATEGIES. RESEARCH IN PROGRESS IS DESIGNED TO FURTHER DEFINE THE DIFFERENTIATING CHARACTERISTICS AND TO EXAMINE GROUP DIFFERENCES IN ADJUSTMENT TO INCARCERATION, RESPONSE TO THE INSTITUTION, AND POSTRELEASE RECIDIVISM. INDIVIDUAL RESPONSE VARIATIONS WITHIN GROUPS WILL BE EXAMINED, AS WILL GROUP RESPONSES TO TREATMENT. FURTHER RESEARCH WILL BE NEEDED TO EXAMINE INDIVIDUAL RESPONSES WITHIN GROUP VARIATIONS IN RESPONSE TO A SPECIFIED TREATMENT MODE AND WITHIN GROUP VARIATIONS IN RESPONSE TO A VARIETY OF TREATMENT MODES. GENERAL APPLICATION OF THE RESULTS OF THE 10 GROUPS TO OTHER SAMPLES IS ALSO BEING INVESTIGATED IN A SAMPLE OF STATE AND FEDERAL FEMALE INMATES AND IN A CALIFORNIA YOUTH AUTHORITY POPULATION CONTAINING A HIGH PROPORTION OF CHICANO OFFENDERS. STUDIES WITH OLDER MALE PRISONERS AND PROBATIONERS ARE ALSO PLANNED. WITHIN GROUP AND INTERGROUP VARIATIONS IN DIFFERING POPULATIONS WILL ALSO REQUIRE STUDY. INDIVIDUAL CHANGES IN GROUP CLASSIFICATION OVER TIME AND CONDITIONS WILL ALSO NEED TO BE RESEARCHED. WHILE THESE STUDIES ARE DESIGNED TO HAVE PRIMARILY PRACTICAL AND CLINICAL UTILITY A NUMBER OF THEORETICAL IMPLICATIONS OF THE TAXONOMY COULD ALSO BE EXPLORED TO ADVANTAGE. SUCH STUDIES COULD EXAMINE PHYSIOLOGICAL, COGNITIVE/PERCEPTUAL, OR ETIOLOGICAL VARIABLES. TWO REFERENCES ARE INCLUDED. FOR THE OTHER PAPERS IN THIS STUDY, SEE NCJ 47695-47699. (JAP)