This article describes research conducted to examine the patterns of alcohol and drug use and self concepts of incarcerated adult offenders in relation to age, gender, and ethnicity in a western state. The purpose of this research was to estimate the extent and variety of alcohol and drug use in the prison population and design a data collection instrument. Individual interviews with every newly admitted sentenced felon (N = 157 men and 39 women) were conducted. Inmates reported nearly universal alcohol use and marijuana use and extensive use of cocaine, crack, heroin, crystal methamphetamine (ice) and using various other schedule drugs, usually in combination with alcohol and other drugs. The problem for the interviewers was not how to elicit admissions of drug use but how to categorize the large number of combinations. Polydrug use, often in combination with alcohol, is the rule, not the exception. Starting, switching and quitting, and combining or substituting drugs is reported by the vast majority of inmates. While patterns varied, it was difficult to discern a special class of drug addicts among the inmates. Our findings suggest that large percentages of prison inmates are frequent substance abusers, perceive problems from use, but are often not interested in drug treatment in prison. Many inmates who by their own reports seem appropriate for alcohol or drug treatment do not seek treatment. This is not influenced by the extent of drug use or experience with previous treatment. Female prisoners seem to be more often and more extensively involved in addicting drugs than male prisoners. This is particularly problematic because there are very few specialized treatment or training programs for women offenders. Since drug use is very widespread, urine monitoring is increasing and continued criminalization of all drugs except alcohol enjoys wide support, correctional agencies must search to develop effective and affordable strategies for dealing with drug use.