The analyses presented here are the product of a multi-faceted collaboration, with the goal of improving the effi ciency and effectiveness of services to one of British Columbia’s most challenging and complex sub-populations. [...] It must be noted, though, that the increase in the number of mentally ill people in the criminal justice system may be as much or more a product of the increase in the use of substances by people with mental illnesses as it is due to the deinstitutionalization of mentally ill patients. [...] In such programs, while diversion from the criminal justice system to the mental health system may occur, the focus of the program is on the identifi cation of mentally ill accused and the provision of appropriate health and human services to them. [...] Analysis of the prevalence and distribution of substance use and mental disorders is a precursor to improving the effi ciency, effectiveness, and completeness of services in association with the corrections system. [...] The anonymous linked database was built through a collaborative effort on the part of Simon Fraser University, the Ministry of Health, the Ministry of Public Safety and Solicitor General (responsible for the Provincial corrections system), and the Ministry of Employment and Income Assistance (MEIA).