Mentally ill jail inmates who were previously served by community mental health centers face three sets of problems: an unplanned disconnect with the mental health agency when they are jailed, inadequate mental health services while they are in jail, and failure to reconnect with the community agency when they exit jail. The Jail Data Link (JDL) project described in this report addresses these problems. JDL represented an improved linkage of the mental health and criminal justice systems. During the project, new detainees with mental health problems were more quickly and accurately identified based on the data linkage, aiding jail decisions on classification and housing. Further, planning for jail discharge started almost immediately after jail arrival in an effort to improve the likelihood of successful reintegration to the community and reduce recidivism.