Data show that 63.6 percent of the male prison population and 61.2 percent of the female prison population are currently incarcerated for an offense that was directly related to substance abuse. Data also show that 52.9 percent of the male inmate population and 43.2 percent of the female inmate population self-reported being under the influence of one or more substances at the time they committed the offense for which they were incarcerated. To determine the substance abuse treatment need of the inmates, participating agencies designed an assessment tool that focuses on the substance abuse history of the inmate. This report recommends that the Department of Corrections consider the feasibility of modifying the method used to classify and identify the program needs of inmates. Also, the levels of substance abuse and treatment needs within the inmate population suggest the need to examine the level and use of substance abuse treatment resources not only while in prison but also while offenders are under community supervision. 10 tables and 12 figures