Three types of cross-sectional studies of IDU's recruited in Sydney were reviewed. Study 2 involved four cross-sectional studies repeated over 4 years and collapsed into one dataset. Data for studies 1 and 3 were collected over a discrete period. Similar recruitment methods were used in all three studies; i.e., participants were either current IDU's, heroin users, or in a methadone maintenance program. No particular ethnic group was targeted, and all participants were volunteers. All interviews were conducted face-to-face with trained interviewers. Data for study 1 were collected in 2000-2001 with a total sample of 399 IDU's (17 percent Indigenous). Data for study 2 were obtained in 1997-2000 for 636 IDU's (19 percent Indigenous); and data for study 3 were collected in 1999 from 150 IDU's (15 percent Indigenous). The studies found that there were few differences between Indigenous and non-Indigenous IDU's; however, there were more female Indigenous IDU's than non-Indigenous IDU's in all studies; this was significant in study 1 (56 percent compared with 33 percent). In each study the lifetime prevalence of incarceration was higher in the Indigenous subjects than the non-Indigenous subjects; however, this difference reached significance only in study 2 (68 percent compared with 49 percent). Indigenous IDU's were more likely to report heroin as their main drug than non-Indigenous IDU's in all studies. This difference reached significance in study 1 (87 percent compared with 76 percent). Indigenous IDU's were less likely to report using a needle or syringe after another person in the last month than non-Indigenous IDU's; however, this difference was not significant in any of the studies. These findings suggest that services may need to be more attuned to the needs of Indigenous IDU's; barriers to treatment must be addressed, along with other IDU needs, such as blood-borne virus testing. Given the high rate of incarceration reported by Indigenous IDU's, prison may be an ideal opportunity to promote treatment and blood-borne virus testing and to address some of the barriers identified by Indigenous IDU's. 4 tables and 9 references