Background: This study investigated the demographic characteristics, service use patterns, and needs of people who were high users of the homeless services, Cook County Jail, or hospital systems in Chicago, Illinois.

Methods: Definitions of "high users" in each system were based on number of stays and days. K-means cluster analysis was performed on the subset of individuals who interacted with all three systems and were high users of at least one system.

Results: Cluster analysis was conducted on 1,232 individuals and revealed three profiles. The largest cluster (N=1,059; 86%) consisted of older single individuals exhibiting high rates of disabling conditions and health issues. A second cluster (N=124; 10%) distinguished a particularly vulnerable subgroup with the highest rates of medical and mental health needs. The final, smallest cluster (N=49; 4%) consisted of predominantly younger Black women with children who exhibited the lowest rates of behavioral health issues, but high hospital use.