The national sample included 1,725 adolescents between 11 and 17 years of age in 1976. Annual reports of delinquent behavior were obtained from 1976 to 1980 in confidential personal interviews. Prevalence rates on a general delinquency scale indicated that most youth had some involvement in delinquent behavior in 1976. An estimated 67 percent of youth reported committing 1 or more of 24 offenses included in the scale. For most youth, delinquency involvement was limited to rather trivial or nonserious offenses. The 67-percent figure remained fairly constant between 1976 and 1980. Prevalence rates for an index offense scale showed that involvement in serious crime decreased substantially over the 4-year period. While the annual proportion of youth involved in some type of delinquent behavior remained relatively constant between 1976 and 1980, the annual rate of offending clearly increased. The rate at which delinquent offenses occurred within the youth population was very high; youth reported an average of 36 offenses in 1976 and 53 offenses in 1980. Appendixes contain supplemental information on the survey sample and items. 312 tables and 18 figures