The Juvenile Statistics Division of the Juvenile Court Judges' Commission compiled the data. Data are given on population changes, arrests, Juvenile Probation Office referrals, referral characteristics, dispositions, commitments, diversions, and transfers to adult courts. Also, delinquency cohort data and comparative data by county are presented. In summary, arrests, probation office referrals, and commitments have remained almost steady for 5 years; a slight decline is perceptible in 1979. The State's juvenile population will soon decrease by about 20 percent. Status arrests have been reduced nearly 50 percent since 1975, and nondelinquency referrals to the county juvenile probation offices have declined by more than 60 percent. The secure detention of such nondelinquency referrals has been reduced by more than 98 percent during these 5 years. The rate of informal adjustment dispositions is 280 percent of the rate during 1974. Since that year, adjudicatory probation and consent decree dispositions have increased 28 percent. The secure detention of delinquents has increased by over 60 percent since 1974, while other court-ordered care placements for delinquents are 368 percent of what they were during 1976. Flow charts, data graphs and tables, and comparison figures for 1974 to 1978 are included. (Author abstract modified)