The article first provides background information on the long-standing problem of people with serious mental illness (PSMI) being processed through the criminal justice system instead of the mental health system. It explores the concept of criminalization and what that term means with respect to current practices related to PSMI. The author argues that true criminalization is a relic of past police practices and is no longer the primary factor that brings PSMI into courts, jails, or prisons. The large increases in the number of PSMI in jails and prisons is believed to be the policy of deinstitutionalizing the mentally ill committed to institutions for treatment. The deinstitutionalization movement was fueled by journalistic stories of patient abuse, effective new medications for treating severe mental illness, Federal entitlement programs that paid for community-based mental health services and the availability of insurance coverage for inpatient psychiatric care in general hospitals. Although deinstitutionalization reduced the populations of State mental hospitals, it never succeeded in providing adequate or well-coordinated outpatient treatment for large percentages of PSMI, particularly those with severe and chronic mental disorders. This led to an increasing number of PSMI bring managed through jail and prison regimes. The increasing involvement of PSMI with the criminal justice system has been largely due to punitive crime control policies and the war on drugs. This article briefly describes programs that have been implemented to serve PSMI under the authority of law enforcement, courts, and corrections. The difficulty of managing PSMI in the criminal justice system is further complicated by mental illness being only one of a number of problems experienced by criminally involved PSMI. 82 references