The longitudinal data presented in this study clearly support the hypothesis of criminalization of the mentally ill. After deinstitutionalization, there were fewer significant differences in the arrest and mental health histories of civil patients and ISTs. Both samples displayed increases in prior hospitalization and arrest records. Among the civil patients, there was a dramatic increase in the frequency and seriousness of criminal activity. These findings indicate that public and law enforcement officials are at an increased risk of being victimized. The criminal justice system will be processing more and more mentally ill offenders as arrest rates among the mentally ill increase. More restrictive civil commitment standards have prevented the hospitalization of mentally ill persons who may deteriorate to the point of becoming violent. The author supports the practice followed in some States of removing the dangerousness standard from their civil commitment process. 4 tables and 28 references