The NYS reports on delinquent behavior, alcohol and drug use, and other types of problem behavior in the American youth population. The 1,725 subjects in the longitudinal survey constituted a national probability sample. Thirteen percent were lost during the course of the study. The subjects, all 17 years old at the time of their initial interviews, reported their involvement in delinquency in confidential personal interviews, usually in the subject's home. Approximately 5 percent of persons at each age were classified as serious violent offenders, committing robberies, aggravated assaults, sexual assaults, or gang fights. Male rates were generally 7 to 8 percent, compared to 2 to 3 percent for females. Prevalence rates increased for males from age 12 to 16 and then declined to age 21. For females, the prevalence rate declined with age. At least 35 percent of the males and 11 percent of the females had been classified as serious violent offenders for at least 1 year by age 21. Self-reports showed higher levels of criminal involvement than did arrest records. Data tables and 121 references. (Author abstract modified)