Physician groups figure prominently among 88 new accountable-care organizations (ACOs) added to the Medicare Shared Savings Program’s participants on July 1, 2012. With the latest announcement from CMS,1 154 organizations are now participating in the initiative, covering more than 2.4 million beneficiaries. According to CMS, almost half of the participants are physician-driven organizations serving fewer than 10,000 beneficiaries. Participating organizations will be required to meet standards for 33 quality measures related to care coordination and patient safety, appropriate use of preventive health services, improved care for at-risk populations, and patient and caregiver experiences of care. The newly announced ACOs run the gamut of size and geographic diversity (with the larger states being particularly well represented). Of the new participants, 10 are based in Florida and six are in California. They range in size from the 29-physician Accountable Healthcare Alliance, PC (East Lansing, Michigan), composed of networks of individual ACO practices that will serve Medicare beneficiaries in Michigan, to the 2,249-physician Mount Sinai Care, LLC (New York, New York), formed of networks of individual ACO practices and hospitals employing ACO professionals (which will serve Medicare beneficiaries in New York). The application period for organizations that wish to participate in the Shared Savings Program beginning in January 2013 was intended to be open from August 1 through September 6, 2012. CMS, however, is no longer accepting applications for the 2013 program year, suggesting that the program is attracting greater interest than anticipated. More information (including application requirements) is available at http://www.cms.gov/Medicare/Medicare-Fee-for-Service-Payment/sharedsavingsprogram/Application.html.