THE JESNESS INVENTORY (JESNESS, 1966) IS INDICATED TO HAVE BEEN DESIGNED TO HELP CLASSIFY TYPES OF DELINQUENTS, PREDICT SOCIAL AND PERSONALITY PROBLEMS, AND ASSESS CHANGE OVER A RELATIVELY SHORT PERIOD. THE TEST CONSISTS OF 10 SCALES AND A DERIVED PREDICTIVE SCORE, THE ASOCIAL INDEX. NOTING THAT THE NECESSITY OF VALID MEASURES OF DELINQUENCY IS OF IMMEDIATE IMPORTANCE IN NORTHERN IRELAND, THE JESNESS INVENTORY WAS SELECTED AS A POTENTIALLY USEFUL INSTRUMENT IN IDENTIFYING AND MONITORING LEVELS OF DEVIANCE AMONG VARIOUS GROUPS IN THE PROVINCE. THE CONCERN OF THIS STUDY IS TO DETERMINE WHETHER THE INSTRUMENT CAN DISTINGUISH BETWEEN DIFFERING LEVELS OF DEVIANCE AND DISCRIMINATE BETWEEN DELINQUENTS AND NONDELINQUENTS. THE INVENTORY WAS PRESENTED ON TAPE TO SMALL GROUPS OF SUBJECTS, WITH THE STATED INTENTION OF HELPING TO OVERCOME LITERACY PROBLEMS, AN ACCEPTED METHOD OF ADMINISTRATION. THREE GROUPS OF SUBJECTS WERE TESTED: (1) 961 BOYS FROM 8 SECONDARY SCHOOLS, (2) 229 BOYS COMMITTED BY THE COURTS TO THE TWO MALE TRAINING SCHOOLS IN THE PROVINCE, AND (3) 95 YOUNG OFFENDERS IN BORSTALS (USED FOR YOUNG ADULT OFFENDERS WHO CANNOT BE LEFT IN THE COMMUNITY, BUT WHO ARE NOT SO DANGEROUS AS TO WARRANT IMPRISONMENT). FIVE OF THE JESNESS SCALES CLEARLY DIFFERENTIATE THE NORMAL SCHOOL GROUP FROM BOTH THE DELINQUENT SAMPLES, I.E., SOCIAL MALADJUSTMENT, VALUE ORIENTATION, ALIENATION, AUTISM, AND THE ASOCIAL INDEX. THREE SCALES--SOCIAL ANXIETY, WITHDRAWAL, AND DENIAL--SHOW NO DIFFERENCE BETWEEN THE GROUPS. IN COMPARING THE TWO DELINQUENT SAMPLES, THE ASOCIAL INDEX IS THE ONLY SCALE TO DISCRIMINATE SIGNIFICANTLY BETWEEN THEM, WITH THE BORSTAL GROUP SCORING SIGNIFICANTLY HIGHER THAN THE TRAINING SCHOOL POPULATION. FINDINGS ARE DISCUSSED WITH REFERENCE TO OTHER BRITISH STUDIES AND TABULAR DATA FROM THE STUDY ARE PROVIDED, ALONG WITH REFERENCES. (RCB)