This document discusses establishing an Extensivist model of care to coordinate care for high-cost, high-need patients. It describes how an Extensivist clinic would function, with an Extensivist leading a care team to provide integrated care for patients' medical, behavioral and social needs. It also outlines challenges in implementing this model, such as gaining hospital privileges, changing patient behaviors, and developing new capabilities. The goal is to improve outcomes and lower costs through coordinated, preventative and patient-centered care for the most complex patients.