As previously reported, CMS has launched several initiatives designed to encourage hospitals, physicians and other providers to participate in “accountable care organizations” (ACOs) that offer cost-effective, coordinated care to Medicare beneficiaries. In addition to issuing a major proposed rule to implement the Affordable Care Act’s (ACA) Medicare Shared Savings Program (under which ACOs that meet certain quality standards and surpass a minimum savings target will be able to share a percentage of Medicare savings), CMS has proposed a "Pioneer ACO Model." The Pioneer ACO Model is designed to provide an opportunity for more rapid escalation of shared savings and risk to advanced ACOs -- that is, organizations with extensive experience with systematic care improvement efforts that are prepared to enter payment arrangements that include financial accountability and performance incentives. While CMS had originally indicated that letters of intent to participate in the Pioneer ACO Model would be due on June 10, 2011, CMS has extended that deadline to June 30, 2011 in response to feedback from potential applicants. Likewise, the deadline for submission of applications has been extended; they now must be postmarked by August 19, 2011 (instead of July 18).