In 2001, drug-use data were obtained from 2,135 adult male inmates in the prisons of 4 Australian jurisdictions. Indigenous offenders represented 25 percent of the sample. In 2002 and 2003, drug-use data were obtained from 5,797 adult male police detainees; 702 (12 percent) were Indigenous offenders. Overall, among both prisoners and police detainees, Indigenous male offenders were more likely to have recently used alcohol, and non-Indigenous offenders were more likely to have recently used a wide range of illicit drugs, including cocaine, heroin, morphine, hallucinogens, and ecstasy. Recent cannabis use was the same for Indigenous and non-Indigenous prisoners, but there was a significant difference in recent use of cannabis by Indigenous and non-Indigenous police detainees, with Indigenous detainees being more likely to self-report using cannabis in their lifetime, in the past 12 months, and in the past 30 days. Compared with non-Indigenous male offenders, Indigenous male offenders were younger, more likely to be married, less educated, and largely unemployed. This suggests that Indigenous offenders experience a number of factors that can lead to drug and alcohol use and abuse. Although both Indigenous and non-Indigenous male offenders had extensive histories and recent use of a wide range of drugs--with the most common (in order of prevalence) being alcohol, cannabis, and amphetamines--drug demand and harm-reduction strategies must be tailored to the use patterns of different groups in specific locations. This includes attention to differences in recent drug use by Indigenous offenders compared with non-Indigenous offenders and by Indigenous prisoners compared with Indigenous police detainees in urban settings. 4 tables and 9 references