The Indigenous offender population has continued to increase over recent years in terms of both numbers and imprisonment rates. This paper examines the impact of a number of data definitions and processing system issues on trends in the full-time Indigenous offender population in NSW. It uses two sets of data, Corrective Service NSW (CSNSW) thirteen year series sourced from Offender Integrated Management System, and the data serious of adult Indigenous estimated resident population (ERP) of NSW sourced from selected from ABS Prisoners in Australia. Firstly, the paper describes changes in CS NSW data collection systems and statistical definitions used to monitor trends in the Indigenous offender population. The impacts of these revisions on Indigenous offender population trends are discussed. Secondly, the paper briefly examines changes in published Indigenous offender imprisonment rates and estimates of the resident adult Indigenous community population in NSW. The impacts of these changes in interpreting trends in the Indigenous offender population are also discussed. In conclusion, the paper outlines some of the background factors that should be borne in mind in review trends in the NSW Indigenous offender population and associated imprisonment rates.