Numerous reports indicate that individuals with serious mental illness (SMI) are overrepresented in the criminal justice system. This review focuses on offenders with schizophrenia, schizoaffective disorder, bipolar disorder, or major depression. Prevalence estimates of SMI among incarcerated adults range from 15 percent to 25 percent. These estimates are three to five times as high as in the general population, in which the prevalence of SMI ranges from 5 percent to 8 percent. Research conducted in the United States found that between 28 percent and 52 percent of those with SMI have been arrested at least once. This review is about interventions provided to offenders with SMI who are detained in a jail, prison, or forensic hospital or who are transitioning from one of these settings back to the community. This is an especially vulnerable population because "jails and prisons have cultures that often lead to maladaptive behaviors in offenders with SMI that subsequently undermine treatment" both in and out of incarceration settings. Jails house inmates who are awaiting adjudication of their cases or who are serving short-term sentences (less than 1 year) for minor offenses, prisons house inmates convicted of more serious crimes for longer durations, and forensic hospitals house offenders for varying lengths of time. Forensic hospitals are often specialized units within State-run psychiatric hospitals. Transitional interventions are usually initiated within 3 months of an inmate's release date and continue once he or she is back in the community (e.g., home/family, halfway house). Programs designed to prevent or minimize incarceration, such as mobile crisis intervention teams or other interventions delivered at the point of contact with the police, are beyond the scope of this report. Also beyond the scope of this report are court-ordered, involuntary treatments intended to restore competency to stand trial and other postbooking strategies, such as mental health courts, designed to divert offenders with SMI to a treatment environment in lieu of incarceration. This report focuses on the comparative effectiveness of interventions provided to offenders with SMI (schizophrenia, schizoaffective disorder, bipolar disorder, or major depression), with or without a co-occurring substance use disorder, during incarceration in jail, prison, or forensic hospital or during transition from incarceration in these settings to the community. An important goal of this review is to describe incarceration-based and incarceration-to-community transitional interventions in a manner that will allow treatment providers to replicate effective treatments and to identify gaps in the scientific literature for future research in the field. This report addresses the following Key Questions (KQs): Key Question 1. What is the comparative effectiveness of interventions applied within a jail, prison, or forensic hospital setting for adults with SMI (schizophrenia, schizoaffective disorder, bipolar disorder, or major depression) with or without a co-occurring alcohol/substance abuse diagnosis? Is there a difference in the comparative effectiveness of interventions based on the setting (jail, prison, forensic hospital) in which the interventions are provided? Key Question 2. What is the comparative effectiveness of incarceration-to-community transitional interventions for adults with SMI (schizophrenia, schizoaffective disorder, bipolar disorder, or major depression) with or without a co-occurring alcohol/substance abuse diagnosis? Is there a difference in the comparative effectiveness of interventions based on the setting (jail to community, prison to community, forensic hospital to community) in which the interventions are provided