Mail surveys, interviews, and site visits were conducted to examine handling of the MIMR offender by the State's lockups and jails, mental health services, courts, and prisons. Results indicate that there exists a population of MIMR offenders who frequently and repeatedly come in contact with the criminal justice system. Most jails in Illinois are not equipped to address the needs of this special population, and programs in prisons have been developed on an ad hoc basis. Major problems identified in the correctional response include lack of access to adequate mental health services, inadequate information and training among court and corrections personnel, and insufficient interagency coordination and cooperation. A significant number of these offenders could be identified and diverted when they come to the attention of police and jails. The courts should be more active in developing and using community-based alternatives to incarceration. Probation should serve the court system by monitoring compliance with court orders, linking offenders with assessment and treatment services, and coordinating activities with community service providers. Systematic screening, monitoring, and diversion to appropriate rehabilitative and habilitative programs would protect MIMR offenders from inappropriate incarceration, better meet their special needs, be more humane, and contribute to public safety. Survey forms and supplemental data are appended. Chapter tables, glossary, and 16 references.