The Center for Medicare and Medicaid Innovation (CMMI) within CMS is tasked with fostering “healthcare transformation by finding new ways to pay for and deliver care that can lower costs and improve care.” An important component of CMMI’s agenda is the accountable care organization (ACO) model in fee-for-service (FFS) traditional Medicare (TM). CMS defines ACOs as “groups of doctors, hospitals, and other health care professionals that work together to give patients high-quality, coordinated service and health care, improve health outcomes, and manage costs. ACOs may be in a specific geographic area and/or focused on patients who have a specific condition, like chronic kidney disease.” The Medicare Shared Savings Program (MSSP) made ACOs a permanent feature of TM in 2012. CMMI’s past ACO models include Pioneer ACO; ACO Investment Model; Advance Payment; Comprehensive ESRD Care, which focuses on end-stage renal disease; and Next Generation ACOs (NGACOs). Current models as of November 2024 include Kidney Care Choices, Making Care Primary, Primary Care First, and Realizing Equity, Access, and Community Health (known as REACH). Currently, one-third of TM beneficiaries are in Medicare’s ACO models, pursuant to CMMI’s goal of having all TM beneficiaries in an accountable care relationship by 2030.