Montefiore Medical Center is an integrated delivery system in the Bronx and lower Westchester and the University Hospital for Albert Einstein College of Medicine. Montefiore provides care for a diverse population with a high rate of chronic disease and low socioeconomic status. This chapter traces the history of Montefiore’s Accountable Care Organization (ACO) development including care management experience prior to the Affordable Care Act, administrative structure, and the use of care management as a central element in its ACO.