The information on substance abuse reflects self-reported drug use during the 6-month period prior to incarceration and scores of 9 or above on the Michigan Alcohol Screening Test (MAST). Based on the self-reports and MAST scores, 67 percent (n=46,446) of the total inmate population, 66 percent (n=43,810) of male inmates, and 70 percent (n=2,636) of female inmates can be identified as substance abusers. These percentages of identified substance abusers in the inmate population must be considered a conservative estimate. If calculations excluded inmates for whom substance use data are missing, an estimated 74 percent (46,446) of the remaining inmates for whom data are available would be classified as substance abusers. The report presents data on drug and alcohol abuse, type of drug use, crime of commitment, region of commitment, minimum sentence, maximum sentence, second felony status, current age, educational level and ethnic background. Tables