The Centers for Medicare & Medicaid Services (CMS) has announced “interim” first year savings data from both the Medicare Shared Savings Program Accountable Care Organizations (ACOs) and the Pioneer ACOs. In its press release, CMS reports that among the 114 Medicare Shared Savings Program ACOs, 54 reduced Medicare expenses by $128 million. 29 of those 54 Medicare ACOs were eligible for shared savings totaling more than $126 million. Updating data reported earlier, CMS also reports that 9 of the 23 remaining Pioneer ACOs (9 Pioneer ACOs left the program after its first year) together reduced Medicare expenses by $147 million. While these initial year one results do show significant reductions in Medicare expenses, the fact that less than half of each type of ACOs achieved the total savings is not encouraging. The level of total savings also is far less than projected, highlighting the challenge of generating significant savings so quickly in a 12-month timeframe. CMS states that “final” first year savings totals will be reported later in 2014.