This paper sought to synthesize what is currently known about mentally ill offenders in American jails and prisons based upon the most recent government and congressional reports and relevant literature review. The primary goal is to provide a detailed picture of the status of mentally ill offenders—including prevalence, basic demographic information, bio-psycho-social status, mental health, and family histories—and also to identify the problems, conditions, and obstacles faced while under the jurisdiction of the criminal justice system. Mentally ill offenders are constitutionally guaranteed basic mental health treatment. A review of the literature indicates that this constitutional guarantee is not being adequately fulfilled. Implications and suggestions for change are discussed.