These guidelines have been prepared as a reference for those involved in collecting and supplying the data for the Alcohol and Other Drug Treatment Services National Minimum Data Set (AODTS-NMDS). Updated guidelines are released for each year of the collection. This edition is relevant to the 2009-10 collection period. These guidelines should be particularly useful to staff in Australian Government, state and territory health departments, and alcohol and other drug treatment agency staff directly involved in the collection and reporting of the data set.