In addition to determining this group's extent of contact with the juvenile justice system, the study addressed the age of onset of offending and the characteristics of offenses. Formal apprehension by police was the measure of contact with the juvenile justice system. There were nearly 21,000 individuals born in 1984 who lived in South Australia between 1994 and 2001, when they were between the ages of 10 and 17. Of this cohort, 16.8 percent were apprehended by police at least once when they were juveniles. Included in this group were 28 juveniles who were apprehended for the first time at age 18 for offenses committed while they were 17 years old or younger. This group was included in most, but not all, of the analyses reported in this paper. Of the 1984 cohort apprehended by police at least once as adolescents, 76.9 percent were male. Indigenous youth were overrepresented by 6.9 percent. The level of overrepresentation was more pronounced for Indigenous females. Of the youth apprehended, 86 percent were apprehended less than 5 times; however, 3.2 percent were apprehended more than 10 times during their adolescence. The average age at first apprehension was 15.2 years. In order of frequency, the offenses for which juveniles were most often apprehended were theft and related offenses, property damage, traffic and vehicle regulatory offenses, breaking and entering, and acts intended to cause injury. The frequency of each type of offense is analyzed in relation to the ages of the offenders. 33 figures, 16 tables, and 4 references