A total of 2,411 male and 304 female inmates were evaluated for substance use disorders using the SUDDS-IV and the DSM-IV diagnosis criteria. Alcohol was the most prevalent drug used, with 31 percent meeting the diagnosis criteria for alcohol dependence and 46 percent meeting the criteria for either alcohol dependence or abuse. Marijuana was the second most prevalent substance abused by inmates, followed by cocaine and other stimulants. Of the inmates who were dependent on drugs, 59 percent were dependent on only one drug. However, there was a great deal of overlap noted between alcohol use and other drug use; 57 percent of the alcohol dependent inmates were also dependent on another substance. Severity indications were also measured in order to understand the severity of the substance dependency. Those inmates who were dependent on marijuana had the fewest dependency indicators, while those dependent on heroin or other opiates had the most severe dependency indicators. Findings are also summarized by gender and by race. Female inmates were noted to have substantially greater severity of substance use disorders than male inmates. Among the male inmates, Caucasians and Native Americans were the most likely to be dependent on at least one substance, while Hispanics were least likely to be dependent. Section 2 of the report discusses issues related to study reliability and validity, while section T3 presents the findings in table format. In conclusion, the findings indicate that a combination of addiction treatment, basic education, and vocational training is required to provide appropriate and effective rehabilitation.