Police respond to calls involving people with mental illnesses which can be complex, requiring a response that reflects the laws, resources and other distinct characteristics of a jurisdiction. A growing number of communities are implementing Specialized Policing Responses (SPRs) that are designed to improve outcomes for everyone involved in these incidents. Although there are many common elements to SPRs, there are also important differences across jurisdictions that should be reflected in the design of any law enforcement-mental health initiative. This study explores the program design process for a variety of SPR modelsincluding crisis intervention teams, law enforcement/mental health co-response teams, and case management approachesthat take into account such factors as jurisdiction size, demographics, mental health and law enforcement agency resources, and relevant State laws. Also considered is how the design may vary depending on the type of problem (such as officer and public safety, frequent repeat calls for service, inefficient or ineffective use of resources, and poor outcomes for people with mental illnesses) that jurisdiction leaders most want to address. This study demonstrates there is no one-size-fits-all approach for law enforcement responses to people with mental illnesses. Quotes from practitioners and examples from several communities from across the country are included, along with detailed lessons learned from four jurisdictions selected for on-site study: Akron, OH; Fort Wayne, IN; Los Angeles, CA; and New River Valley, VA. Appendixes