The mean age at first heroin use was 19 years, (SD 6.0, range 9–43 years) and the mean age of first injection was 21 years (SD 6.3, range 13–43 years). The mean age of first heroin use and first heroin injection was similar for males (18 years for both) and females (18 and 19 years, respectively). There were no differences in terms of ethnicity for either age of first heroin use (18 years for all groups) or first heroin injection (18, 19 and 18 years for Australians, 'other Australians' and Indigenous Australians respectively).
