About 2,000 youths aged 12 to 18 were interviewed and divided into 5 groups. There were juveniles who reported no offenses, who reported offenses but no police contact, who reported both offenses and police contacts, who reported offenses and had recorded police contact, and who reported offenses and had to appear before the public prosecutor. The study instrument was a structured interview schedule; self-reported delinquency and police contacts were validated in the police files. The youths were asked questions about the nature and frequency of delinquency; family, school, and social integration; contacts with the juvenile justice system; leisure time; and values and norms. About half the youths reported at least one out of the seven offenses they were asked about, and about one-third of the youths interviewed revealed a more serious pattern of offenses. Girls were found to be more conforming than boys in all respects, and social status was only slightly related to delinquent behavior. Failure in school was determined to be the most important determinant of delinquency. Forty tables, 4 figures, and 18 references are included.