THE SUBJECTS WERE FROM A FOLLOWUP STUDY OF INVESTIGATION INITIATED IN 1964 BY THE CENTER FOR STUDIES IN CRIMINOLOGY AND CRIMINAL LAW AT THE UNIVERSITY OF PENNSYLVANIA. THE ORIGINAL STUDY, PUBLISHED AS 'DELINQUENCY IN A BIRTH COHORT,' WAS A COMPREHENSIVE ANALYSIS OF A COHORT OF MALES BORN IN 1945 WHO LIVED IN PHILADELPHIA FROM THEIR TENTH TO THEIR EIGHTEENTH BIRTHDAY. DATA WERE GATHERED ON 9,945 SUBJECTS. OF THIS NUMBER, A WORKING SAMPLE OF 567 SUBJECTS, 26 YEARS OF AGE CONSIDERED REPRESENTATIVE OF THE ORIGINAL SAMPLE WAS INTERVIEWED FOR THE PRESENT STUDY. DATA WERE COLLECTED BY MEANS OF A PERSONAL INTERVIEW WITH EACH OF THE SUBJECTS. THE STRUCTURED INTERVIEW CONSISTED OF 231 CLOSED AND OPEN-ENDED QUESTIONS DESIGNED TO ELICIT DATA ON THE LIFE HISTORY OF THE SUBJECT UP TO THE AGE OF 26. THE FOLLOWING PROPOSITIONS SUMMARIZE STUDY FINDINGS: (1) THE OVERALL INCIDENCE AND SERIOUSNESS OF SELF-REPORTED DELINQUENT BEHAVIOR ARE APPROXIMATELY EVENLY DISTRIBUTED ACROSS SOCIOECONOMIC STATUS LEVELS; (2) OFFICIAL DELINQUENTS REPORT A HIGHER OVERALL INCIDENCE AND SERIOUSNESS FOR THEIR HIDDEN DELINQUENCY THAN DO OFFICIAL NONDELINQUENTS; (3) MEMBERSHIP IN A GANG OR DELINQUENT SUBCULTURE STIMULATES A VERY HIGH OVERALL INCIDENCE AND SERIOUSNESS OF OFFENSE; (4) THE INCIDENCE AND SERIOUSNESS OF HIDDEN JUVENILE DELINQUENCY HAS A STRONG, POSITIVE RELATIONSHIP TO THE OVERALL INCIDENCE AND SERIOUSNESS OF HIDDEN ADULT CRIME; (5) WITH THE EXCEPTION OF ADULT SERIOUSNESS, THERE ARE NO RACIAL DISPARITIES IN THE OFFENSE AND SERIOUSNESS RATES OF SELF-REPORTED DELINQUENCY AND CRIME; AND (6) SUBJECTS WHO HAVE OFFICIAL ARRESTS AS JUVENILES OR ADULTS REPORT A HIGHER INCIDENCE AND SERIOUSNESS IN THEIR HIDDEN OFFENSES THAN OFFICIAL NONOFFENDERS. THESE FINDINGS ARE COMPARED TO ANALOGOUS STATISTICS IN OFFICIAL DATA. THE APPENDIXES INCLUDE A SAMPLE OF THE QUESTIONNAIRE, DATA OBTAINED IN THE STUDY, AND THE RESULTS OF ANALYSIS. (RCB)