The Correctional Service of Canada (CSC) conducted a national survey to assess the mental health status of Federal inmates in 1988. The survey relied on a structured interviewing instrument called the Diagnostic Interview Schedule (DIS). Provisions were embedded in the Offender Intake Assessment (OIA) process to permit estimation of trends and to alert managers where additional assessments would be warranted. Mental health indicators were collected with reference to both the “current” and “previous” status of the offender. Flow trends were examined by analyzing OIAs for male and female admissions from 1997 to 2001. The data show a significant increase in the number and proportion of positive assessments on the mental health indicators embedded in OIA. The proportion of Federal inmates with an assessed prior history of mental illness was also found to have increased during this period. Based on these results, it is clear that the percentage of the Federal population with mental health problems is growing, even though overall prison admission and the institutional population counts have been in decline. Although mentally disordered offenders still represent a relatively small proportion of the overall population, this fact is still a matter of concern. Managing offenders with mental health issues presents additional challenges beyond those normally associated with Federal offenders. These inmates require special assistance to enhance their abilities to cope with daily prison life. They often require special supervision, accommodation, and interventions. 2 figures, 5 tables, 7 notes