The essential elements outlined in this document apply to specialized probation responses to people with mental illnesses that focus primarily on initiatives in which participants have been adjudicated and sentenced to participate, with conditions, in a specialized probation initiative after or in lieu of a jail term. Each of the 10 essential elements contains a short statement describing criteria that specialized probation initiatives should meet in order to be effective, followed by an explanation of the element's importance and how its principles can be achieved. This report is meant to guide agents of change in communities that want to develop a specialized probation intervention. It can be used as a practical planning tool at each stage of the process (designing the initiative, developing or enhancing policies and procedures, monitoring practices, and conducting evaluations). It can also be used by personnel from seasoned, longstanding initiatives to improve the organization and functioning of an existing effort. This document is intended to be a "living document" that will be updated or supplemented as specialized probation responses mature, incorporating new research findings that can provide a stronger base of knowledge about how these initiatives can best impact the community, as well as the relative importance of each of the essential elements. Data were collected from a variety of sources, including the experiences of probation officials, mental health professionals, advocates, and consumers of mental health services, as well as a review of the scholarly and policy literature. 1 figure