THE FULL RANGE OF DELINQUENT ACTS WAS INCLUDED IN THE INTERVIEW TO DETERMINE WHETHER DELINQUENCY IN THE STUDY POPULATION WAS A SPECIALIZED OR HETEROGENEOUS ACTIVITY. THE RELATIONSHIP BETWEEN THE RANGE OF DELINQUENT ACTS AND THE FREQUENCY OF COMMITTAL OF ANY ACT WAS EXAMINED ALSO. THE BOYS LIVED AND ATTENDED SCHOOL IN A MODERN, PREDOMINANTLY WORKING-CLASS AREA IN ENGLAND. FIFTY-FOUR BOYS 11-12 YEARS OF AGE WERE INCLUED IN THE FIRST SELF-REPORTING INTERVIEW, AND 51 BOYS 13-14 YEARS OF AGES WERE INCLUDED IN THE SECOND. PATTERNS OF GROUP FORMATION AND SOCIAL ACTIVITIES WERE AGE RELATED. FORTY-EIGHT ITEMS ON THE SELF-REPORTING DELINQUENCY INTERVIEW WERE DESIGNED TO ELICIT INFORMATION ABOUT THE AMOUNT OF CRIME COMMITTED WHETHER DELINQUENCY WAS A SPECIALIZED ACTIVITY, PROBLEMS OF MEMORY AND CONCEALMENT, CONTACT WITH THE POLICE, AND TYPE OF OFFENSE. THE LEVEL OF CRIME COMMITTED APPEARED TO BE MUCH GREATER THAN THE LEVEL ADMITTED. BOYS WHO COMMITTED MORE OFFENSES ALSO COMMITTED A MORE VARIED RANGE OF OFFENSE. THERE WAS SOME EVIDENCE OF SPECIALIZATION IN TYPES OF OFFENSES COMMITTED AT 13-14 YEARS, THIS SPECIALIZATION BEING LINKED TO PATTERNS OF GROUP FORMATION AND GROUP-RELATED OFFENSE. MISBEHAVIOR, SUCH AS SMOKING AND TRUANCY, ALSO WAS LINKED TO THE GENERAL FACTOR OF DELINQUENCY. RESPONSES TO PARTICULAR ITEMS ON THE INTERVIEW FORM WERE MUCH MORE VARIABLE THAN RESPONSES TO ALL ITEMS IN GENERAL. BOYS WHO COMMITTED MORE OFFENSES WERE MORE LIKELY TO HAVE BEEN CONVICTED, FORMALLY CAUTIONED, OR INFORMALLY WARNED BY THE POLICE. THE SERIOUSNESS OF OUTCOME WAS RELATED TO THE NUMBER OF TYPES OF CRIMES ADMITTED IN A POSITIVE DIRECTION. MOST DELINQUENT ACTIVITIES INVOLVED OTHER BOYS, AND VERY LITTLE CRIME WAS COMMITTED WITH ADULTS. GROUP OFFENSES WERE SUGGESTED MORE OFTEN BY OTHER BOYS THAN BY THE BOY HIMSELF, WITH THE ROLE OF ADULT PARTICIPATION BEING NEGLIGIBLE. IT IS CONCLUDED THAT DELINQUENCY IS HETEROGENIOUS RATHER THAN SPECIALIZED ACTIVITY AND THAT THE SELF-REPORTING DELINQUENCY INTERVIEW ALLOWS FOR THE STUDY OF SOCIAL PARAMETERS OF DELINQUENT ACTS AND THE RELATIONSHIP OF THESE ACTS TO ACTIVITY PATTERNS IN A MORE EFFECTIVE MANNER THAN DOES THE STUDY OF OFFICIAL CONVICTIONS. SUPPORTING DATA, REFERENCES, AND A LIST OF ITEMS IN THE SELF-REPORTING DELINQUENCY INTERVIEW ARE INCLUDED. (DEP)