Within two years of embarking on its quest to establish an accountable care organization, the Cambridge Health Alliance, a large public safety-net health system in Massachusetts, was well on its way to transforming health care delivery for the vulnerable populations it serves. In a new Commonwealth Fund case study, Karen Hacker of the Institute for Community Health and colleagues describe the organization’s four major strategies: establishing medical homes, entering alternative payment arrangements with managed care organizations, launching a care management program for complex patients, and establishing a partnership with a tertiary care institution.