Main findings from the period 2000 through 2001 and 2003 through 2004 indicated that the number of young persons under juvenile supervision declined by approximately 5 percent nationally. Approximately 12,900 young people were under supervision orders in Australia each year, including about 10,000 who were aged 10 through 17 years. Data about juvenile offenders revealed that nearly two-thirds of juvenile offenders were at least 15 years old when they experienced their first juvenile supervision order. Community supervision was much more common than detention-based supervision throughout the study period, although differences in the length and type of supervision were noted by age, sex, and Indigenous status. The majority of juveniles under supervision were males, nearly three-quarters were aged 14 to 17 years, and over 30 percent were Aboriginal. The supervision periods ranged from less than 7 days to 12 months or longer, and the median periods were 3 to 6 months. The average length of detention-based supervision in Australia during 2003 through 2004 was 792 days. The NMDS includes three datasets and data that are extracted from the administrative systems of the State and territory departments responsible for juvenile justice in Australia: (1) young people under juvenile justice supervision; (2) juvenile justice supervision periods; and (3) juvenile justice centers. The appendix includes a description of the key elements of the juvenile justice systems in each State and territory in Australia. Tables, figures, appendixes, glossary, and references