This report is based on the Juvenile Justice National Minimum Data Set (NMDS), which contains three data collections: young people under juvenile justice supervision, juvenile justice episodes (supervision periods), and juvenile justice centers. Results suggest that the number of young people under juvenile justice supervision declined from 2000-2001 and 2003-2004 by approximately 5 percent nationally (excluding Australian Capital Territory for which data are not available for earlier years); that the rate for 10- to 17-year-olds under juvenile justice supervision declined from 4.8 per 1,000 to 4.5 per 1,000; that almost two-thirds of young people were at least 15 years old when they had their first ever juvenile justice supervision; that most young people completed one supervision period during a year, with community-based supervision being much more common than detention-based; that very short supervision periods were more likely to include episodes of pre-sentence remand; and that supervision periods of medium or longer lengths were more likely to include episodes of sentenced detention or community based supervision respectively. Differences were found according to demographics such as age, sex and indigenous status in both the length and type of supervision. These data, which include both community-based and detention-based supervision, were collected by the AIHW from the departments in each State and territory with particular responsibility for juvenile justice. Tables, figures, references, glossary, and appendixes