The need for mental health services in correctional facilities has been established in the literature, but better description is needed about what constitutes mental health care within jails. A detailed examination of service activity enhances understanding about who receives mental health services while incarcerated and to what extent. This type of description is essential in order to begin to assess the appropriateness and adequacy of care and to guide future efforts related to resource allocation and program design, development, and evaluation. This study used retrospective review of inmate health and mental health records. A disproportionate stratified systematic random sample was drawn from a list of inmates housed in the Mental Health Units (MHU) from March through November 1998. Results show that there was a longer average stay on the MHU and greater number of service episodes for men compared to women and for whites compared to persons of color. There was a non-significant trend for white patients in a forensic psychiatric unit to have a longer stay than Black patients. Schizophrenics or inmates with other psychotic disorders received significantly more service episodes than inmates without this type of diagnosis did. On average, inmates with substance-related disorders spent considerably less time on the MHU, and inmates with adjustment orders received less clinical attention while there. Some notable programs that show promise for treatment of mentally ill inmates are jail-to-street transitional case management services, housing for the homeless mentally ill upon release, and attention to treating dual diagnoses. Structuring short-term interventions around stabilization and the development of community-based care plans for inmates likely to be released quickly might be a useful way to use the assessment information gathered soon after jail entry. Even the inmates that stay longer could benefit from coordinated care plans upon their release. 5 tables, 20 references