Encounters with individuals who have mental illness account for only a small proportion of police emergency calls. However, the repetitive nature of these situations and their sometimes fatal outcomes have spurred advocates and law enforcement personnel to seek changes. Findings from a Montreal study illustrate the heavy demands that such calls place on police resources. In an analysis of data from more than 6,100 police encounters, Yanick Charette, M.Sc., and colleagues found that those involving people with mental illness (4.4%) were more likely to result in arrest, even though the offenses were less severe, and that officers spent nearly twice the number of work hours handling such calls (page 511). A widely implemented approach is the crisis intervention team (CIT) model, in which police officers receive 40 hours of specialized training to become first responders to calls involving people with mental illness. In a two-part study, researchers measured the effects of CIT training both on officers’ knowledge and attitudes and on their behavior during emergency encounters. Michael T. Compton, M.D., M.P.H., and colleagues conducted in-depth assessments of nearly 600 officers with and without CIT training and found that such training resulted in sizable and persisting improvements in knowledge, attitudes, and self-efficacy (page 517). The effectiveness of CIT training was also supported by data from the trained officers’ emergency encounters, which were more likely to result in referral or transport to services, rather than arrest—a form of prebooking jail diversion (page 523). In a commentary, Fred C. Osher, M.D., calls for stronger partnerships between the criminal justice and mental health systems, with more clinician training on criminal proceedings (page 403). Finally, this month’s Open Forum reviews the conceptual framework of the CIT model and empirical evidence of its effectiveness. Amanda Brown Cross, Ph.D., and colleagues then outline research needs in this area. Their proposed agenda addresses two major gaps: verifying that changes in officers’ attitudes and skills translate into behavioral change and determining how criminal justice–mental health partnerships affect officers’ behavior (page 530).