In 2015, the Office of Diversion and Reentry Division (ODR), an internal department of the Los Angeles County Department of Health Services, was created to redirect individuals with serious mental illness from the criminal justice system. Part of ODR’s mission is to identify individuals currently incarcerated in a Los Angeles County jail who are experiencing a serious mental health disorder and, to the extent practical, provide them with appropriate community-based care with the goals of reducing recidivism and improving health outcomes. Such redirection from the traditional criminal justice process is often characterized as diversion. To better build and scale efforts to support this work, in 2018, the Los Angeles County’s Board of Supervisors asked for a study of the existing county jail mental health population to identify those who would likely be eligible for diversion based on legal and clinical factors. The resulting report from the RAND Corporation found that an estimated 61 percent of the jail mental health population were likely appropriate candidates for diversion; 7 percent were potentially appropriate; and 32 percent were likely not appropriate candidates for diversion. These findings can help the county determine how it would need to scale community-based treatment programs to accommodate these individuals. The authors also provide recommendations for future programming and research.