Presents survey data on offenders who were in prison or jail or on probation and who reported prior treatment for a mental or emotional problem. About 10% of prison and jail inmates reported a mental or emotional condition; and 10% said they had stayed overnight in a mental hospital or program. Together, 16% or an estimated 283,800 inmates reported either a mental condition or an overnight stay in a mental hospital, and were identified as mentally ill. The report examines the characteristics of mentally impaired offenders, including sex, age, race, and Hispanic origin; provides data on current offense, criminal history, and substance abuse; and describes their mental health treatment since admission to jail or prison. Findings are based on self-reported data from the 1997 Survey of Inmates in State and Federal Correctional Facilities, the 1996 Survey of Inmates in Local Jails, and the 1995 Survey of Adults on Probation.