Clients accessing alcohol and other drug treatment services across Australia commonly have multiple episodes of treatment spanning several years. This report categorises 3 client groups based on their patterns of service use between 1 July 2014 and 30 June 2018. While there were subtle differences in principal drug of concern and some aspects of service use between the 3 groups, overall there were many similarities. This highlights the complexities of characterising alcohol and other drug service users.