Largely the result of prison officials needing to safely and efficiently manage a volatile inmate population, administrative segregation or supermax facilities are criticized as violating basic human needs, particularly for mentally ill inmates. The present study compared Colorado offenders with mental illness (OMIs) to nonOMIs in segregated and non-segregated environments. OMIs committed a large portion of institutional misbehaviors, likely a symptomatic expression of their illness, causing them to be placed at a disproportionately high rate in segregation. Even when OMIs cannot be managed in a less restrictive setting, corrections officials must provide enhanced services to monitor their psychological well-being. (Contains 4 tables and 2 figures.)