The need to portray accurately the level of functioning and severity of psy
chiatric symptoms among mentally ill offenders (MIOs) is paramount from sev
eral perspectives. The prison environment may cast aspersions on the reliab
ility and validity of commonly used functional assessment tools. In additio
n, these tools do not capture environment-specific areas that may be of int
erest to the courts, clinicians. community mental health centers, and other
correctional facilities. Male MIOs (n = 61) who had been treated for at le
ast three months in a (male) Washington state prison mental health program
were evaluated using clinical assessment tools, data abstraction from medic
al records, and structured assessments from correctional officers. Clinical
assessments occurred at their current site of incarceration. The semistruc
tured clinical assessments had high construct validity and correlation for
psychiatric symptoms and diagnosis. The ability of evaluators to determine
accurately relative treatment compliance within the prison was low compared
with the reports from correctional staff, particularly with respect to att
endance at programs. In general, the officers did not recognize lack of pro
gram participation and reclusive behavior as potential signs of mental illn
ess. Despite a significant history of psychiatric symptoms severe enough to
warrant inpatient treatment, 70 percent of the MIO individuals were functi
oning reasonably well in a general population. A fully informed functional
assessment of MIOs likely requires input from both clinicians and correctio
nal officers.