An Accountable Care Organization (ACO) is a formal group of physicians, hospitals, or other care providers that voluntarily work together to deliver high-quality coordinated care to Medicare beneficiaries. The goal of an ACO is to provide affordable care through reducing or eliminating unnecessary duplication of tests or services, lowering the risk of medical errors. For each ACO, there is a defined patient population, primarily composed of Medicare beneficiaries, for which it is held accountable in terms of care cost, gross savings, and quality. 

The following list highlights the top 25 ACOs by patient population, representing over 15.7 million patients with an average population of 628,000.  Of the top 25, 92 percent are classified as commercial ACOs— an ACO model with a non-government payer.

TMA PracticeEdge, a commercial ACO based out of Austin, TX, ranks first with a patient population of five million — 112-percent higher than the next highest ACO, Aetna-Children’s Hospital of Philadelphia (CHOP) which has a patient population of 1.4 million. 

Top 25 Accountable Care Organizations by Patient Population 

Definitive's Healthcare Insights are developed with data from the Definitive Healthcare platform. Want even more insights? Start a Free Trial now and get access to the highest quality data and intelligence on hospitals, physicians, and other healthcare providers.

RankDefinitive IDACO NameACO TypeCityStateACO Start DatePatient PopulationExplore This Dataset
1810909TMAPracticeEdge(Texas Medical Association - Blue Cross and Blue Shield of Texas ACO)Commercial ACOAustinTX2015 Q15,000,000Explore This Profile
2842940Aetna -ChildrensHospital of Philadelphia (CHOP) ACOCommercial ACOPhiladelphiaPA2015 Q41,400,000Explore This Profile
3552096Steward Integrated Care NetworkMedicare Next Generation ACONeedhamMA2016 Q11,000,000Explore This Profile
3552289Aetna - Carilion Clinic ACOCommercial ACORoanokeVA2011 Q31,000,000Explore This Profile
5552388CapitalBluecross- Heritage Medical Group ACOCommercial ACOLemoynePA2011 Q2700,000Explore This Profile
6579844Anthem Blue Cross of California - Healthcare Partners ACOCommercial ACOTorranceCA2013 Q4675,000Explore This Profile
7579912Aetna - Riverside Health System ACOCommercial ACONewport NewsVA2013 Q2500,000Explore This Profile
7585269Horizon Blue Cross Blue Shield of New Jersey - Partners in Care ACOCommercial ACOEast BrunswickNJ2014 Q1500,000Explore This Profile
9823406Aetna - Virtual Medical Group ACOCommercial ACOMarltonNJ2015 Q1400,000Explore This Profile
10552285AdvocatecareACOCommercial ACOChicagoIL2011 Q1375,000Explore This Profile
10969400BCBS Illinois - Advocate Physician Partners Accountable CareCommercial ACORolling MeadowsIL2012 Q3375,000Explore This Profile
12969315BCBS Arizona - Banner Health Network ACOCommercial ACOPhoenixAZ2012 Q1350,000Explore This Profile
12553402Cigna - Banner Health Network ACOCommercial ACOPhoenixAZ2012 Q4350,000Explore This Profile
14577487UnitedHealthcare - Seton Health Alliance ACOCommercial ACOAustinTX2013 Q3320,000Explore This Profile
15578002Partners for Kids ACOMedicaid ACOColumbusOH2012 Q3300,000Explore This Profile
15969460HealthPartners - Northwest Metro AllianceCommercial ACOBloomingtonMN2010 Q1 300,000Explore This Profile
17585460Blue Shield of California - EPIC ACOCommercial ACORedlandsCA2014 Q1273,000Explore This Profile
18835846University Hospitals - Anthem Blue Cross and Blue Shield ACOCommercial ACOClevelandOH2015 Q3270,000Explore This Profile
19849729Humana - DeKalb PHO ACOCommercial ACODecaturGA2016 Q1250,000Explore This Profile
19858080DeKalb Medical Physicians Group - UnitedHealthcare ACOCommercial ACODecaturGA2016 Q3250,000Explore This Profile
19947978Cigna - DeKalb Physicians Health OrganizationCommercial ACODecaturGA2015 Q4250,000Explore This Profile
22552351Cigna -WestmedMedical Group ACOCommercial ACOPurchaseNY2012 Q2237,000Explore This Profile
23553396OptumCare- North American Medical Management California ACOCommercial ACOOntarioCA2012 Q4229,000Explore This Profile
24574791Rainbow Care ConnectionCommercial ACOClevelandOH2012 Q3200,000Explore This Profile
24777076Health Choice UtahMedicaid ACOSouth JordanUT2013 Q1200,000Explore This Profile

Fig 1.  Data from Definitive Healthcare from the Accountable Care Organizations Database. Data is from the Center for Medicare & Medicaid Services and Definitive Healthcare proprietary data. Most recent data available, accessed in April 2020.