THIS STUDY PROFILES THE COMPLAINANTS IN JUVENILE CASES; AND EXAMINES THE CONDITIONS, ACTS, OR INCIDENTS WHICH COMPLAINANTS REPORT; AND THE LEGALLY SUBSTANTIVE OR MORAL INTERESTS OF COMPLAINANTS WHICH ARE SERVED BY THE POLICE WHEN THEY TAKE A JUVENILE INTO CUSTODY. DATA WERE COLLECTED AS PART OF THE POLICING OF JUVENILES PROJECT, AN 18-MONTH PARTICIPANT OBSERVER STUDY FOCUSING ON DAILY ASPECTS OF POLICE HANDLING OF JUVENILES IN CHICAGO, ILL. ALSO, ALL ARREST REPORTS COMPLETED ON JUVENILES TAKEN INTO CUSTODY AND OFFICIALLY PROCESSED IN EACH TARGET DISTRICT WERE COLLECTED. DATA WERE EXAMINED FOR CONTENT AND SORTED INTO 'POLICE CASES' ON THE BASIS OF WHO INITIATED THE COMPLAINT THAT LED TO THE JUVENILE'S ARREST. DATA SHOW THAT BROAD-RANGING INTERPERSONAL PROBLEMS ARE BROUGHT TO POLICE ATTENTION BY CITIZEN COMPLAINANTS. FURTHER, COMPLAINANTS FREQUENTLY PREFER, OR EVEN DEMAND, THAT THE JUVENILE BE TAKEN INTO CUSTODY AS A RESOLUTION TO THE PROBLEM CAUSING THE COMPLAINT. MOST OF THE INTERPERSONAL PROBLEMS ABOUT WHICH COMPLAINTS WERE LODGED WERE OF MINOR LEGAL SIGNIFICANCE. LEGAL ISSUES AND PRIORITIES WERE LESS SIGNIFICANT INFLUENCES ON POLICE REACTION THAN THE COMPLAINANTS' PERCEPTIONS OF JUVENILE BEHAVIOR. THIS MORAL-LEGAL NEXUS SHOULD BE ANALYZED IN ANY EFFORTS TO DEVELOP POLICY FOR POLICE HANDLING OF JUVENILES. TABULAR DATA ARE PROVIDED. (RCB)