The 2010 healthcare law encourages the development of accountable-care organizations as a way to improve care and reduce costs. So what exactly are accountable-care organizations, anyway? In broad outline, these entities propose to unite doctors and clinics or hospitals in groups that pool their resources with the goal of trimming spending while boosting the quality of care. When the group can show that it is improving care and delivers it for less than the cost projected—arrived at by crunching historical patient data for that market—a share of the savings goes to the ACO's bottom line. ACOs exist more on paper than in reality, for now. But a few organizations up and running for decades do closely resemble how the concept can work.